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diff --git a/src/pager.c b/src/pager.c new file mode 100644 index 0000000..37588f0 --- /dev/null +++ b/src/pager.c @@ -0,0 +1,7800 @@ +/* +** 2001 September 15 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** This is the implementation of the page cache subsystem or "pager". +** +** The pager is used to access a database disk file. It implements +** atomic commit and rollback through the use of a journal file that +** is separate from the database file. The pager also implements file +** locking to prevent two processes from writing the same database +** file simultaneously, or one process from reading the database while +** another is writing. +*/ +#ifndef SQLITE_OMIT_DISKIO +#include "sqliteInt.h" +#include "wal.h" + + +/******************* NOTES ON THE DESIGN OF THE PAGER ************************ +** +** This comment block describes invariants that hold when using a rollback +** journal. These invariants do not apply for journal_mode=WAL, +** journal_mode=MEMORY, or journal_mode=OFF. +** +** Within this comment block, a page is deemed to have been synced +** automatically as soon as it is written when PRAGMA synchronous=OFF. +** Otherwise, the page is not synced until the xSync method of the VFS +** is called successfully on the file containing the page. +** +** Definition: A page of the database file is said to be "overwriteable" if +** one or more of the following are true about the page: +** +** (a) The original content of the page as it was at the beginning of +** the transaction has been written into the rollback journal and +** synced. +** +** (b) The page was a freelist leaf page at the start of the transaction. +** +** (c) The page number is greater than the largest page that existed in +** the database file at the start of the transaction. +** +** (1) A page of the database file is never overwritten unless one of the +** following are true: +** +** (a) The page and all other pages on the same sector are overwriteable. +** +** (b) The atomic page write optimization is enabled, and the entire +** transaction other than the update of the transaction sequence +** number consists of a single page change. +** +** (2) The content of a page written into the rollback journal exactly matches +** both the content in the database when the rollback journal was written +** and the content in the database at the beginning of the current +** transaction. +** +** (3) Writes to the database file are an integer multiple of the page size +** in length and are aligned on a page boundary. +** +** (4) Reads from the database file are either aligned on a page boundary and +** an integer multiple of the page size in length or are taken from the +** first 100 bytes of the database file. +** +** (5) All writes to the database file are synced prior to the rollback journal +** being deleted, truncated, or zeroed. +** +** (6) If a super-journal file is used, then all writes to the database file +** are synced prior to the super-journal being deleted. +** +** Definition: Two databases (or the same database at two points it time) +** are said to be "logically equivalent" if they give the same answer to +** all queries. Note in particular the content of freelist leaf +** pages can be changed arbitrarily without affecting the logical equivalence +** of the database. +** +** (7) At any time, if any subset, including the empty set and the total set, +** of the unsynced changes to a rollback journal are removed and the +** journal is rolled back, the resulting database file will be logically +** equivalent to the database file at the beginning of the transaction. +** +** (8) When a transaction is rolled back, the xTruncate method of the VFS +** is called to restore the database file to the same size it was at +** the beginning of the transaction. (In some VFSes, the xTruncate +** method is a no-op, but that does not change the fact the SQLite will +** invoke it.) +** +** (9) Whenever the database file is modified, at least one bit in the range +** of bytes from 24 through 39 inclusive will be changed prior to releasing +** the EXCLUSIVE lock, thus signaling other connections on the same +** database to flush their caches. +** +** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less +** than one billion transactions. +** +** (11) A database file is well-formed at the beginning and at the conclusion +** of every transaction. +** +** (12) An EXCLUSIVE lock is held on the database file when writing to +** the database file. +** +** (13) A SHARED lock is held on the database file while reading any +** content out of the database file. +** +******************************************************************************/ + +/* +** Macros for troubleshooting. Normally turned off +*/ +#if 0 +int sqlite3PagerTrace=1; /* True to enable tracing */ +#define sqlite3DebugPrintf printf +#define PAGERTRACE(X) if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; } +#else +#define PAGERTRACE(X) +#endif + +/* +** The following two macros are used within the PAGERTRACE() macros above +** to print out file-descriptors. +** +** PAGERID() takes a pointer to a Pager struct as its argument. The +** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file +** struct as its argument. +*/ +#define PAGERID(p) (SQLITE_PTR_TO_INT(p->fd)) +#define FILEHANDLEID(fd) (SQLITE_PTR_TO_INT(fd)) + +/* +** The Pager.eState variable stores the current 'state' of a pager. A +** pager may be in any one of the seven states shown in the following +** state diagram. +** +** OPEN <------+------+ +** | | | +** V | | +** +---------> READER-------+ | +** | | | +** | V | +** |<-------WRITER_LOCKED------> ERROR +** | | ^ +** | V | +** |<------WRITER_CACHEMOD-------->| +** | | | +** | V | +** |<-------WRITER_DBMOD---------->| +** | | | +** | V | +** +<------WRITER_FINISHED-------->+ +** +** +** List of state transitions and the C [function] that performs each: +** +** OPEN -> READER [sqlite3PagerSharedLock] +** READER -> OPEN [pager_unlock] +** +** READER -> WRITER_LOCKED [sqlite3PagerBegin] +** WRITER_LOCKED -> WRITER_CACHEMOD [pager_open_journal] +** WRITER_CACHEMOD -> WRITER_DBMOD [syncJournal] +** WRITER_DBMOD -> WRITER_FINISHED [sqlite3PagerCommitPhaseOne] +** WRITER_*** -> READER [pager_end_transaction] +** +** WRITER_*** -> ERROR [pager_error] +** ERROR -> OPEN [pager_unlock] +** +** +** OPEN: +** +** The pager starts up in this state. Nothing is guaranteed in this +** state - the file may or may not be locked and the database size is +** unknown. The database may not be read or written. +** +** * No read or write transaction is active. +** * Any lock, or no lock at all, may be held on the database file. +** * The dbSize, dbOrigSize and dbFileSize variables may not be trusted. +** +** READER: +** +** In this state all the requirements for reading the database in +** rollback (non-WAL) mode are met. Unless the pager is (or recently +** was) in exclusive-locking mode, a user-level read transaction is +** open. The database size is known in this state. +** +** A connection running with locking_mode=normal enters this state when +** it opens a read-transaction on the database and returns to state +** OPEN after the read-transaction is completed. However a connection +** running in locking_mode=exclusive (including temp databases) remains in +** this state even after the read-transaction is closed. The only way +** a locking_mode=exclusive connection can transition from READER to OPEN +** is via the ERROR state (see below). +** +** * A read transaction may be active (but a write-transaction cannot). +** * A SHARED or greater lock is held on the database file. +** * The dbSize variable may be trusted (even if a user-level read +** transaction is not active). The dbOrigSize and dbFileSize variables +** may not be trusted at this point. +** * If the database is a WAL database, then the WAL connection is open. +** * Even if a read-transaction is not open, it is guaranteed that +** there is no hot-journal in the file-system. +** +** WRITER_LOCKED: +** +** The pager moves to this state from READER when a write-transaction +** is first opened on the database. In WRITER_LOCKED state, all locks +** required to start a write-transaction are held, but no actual +** modifications to the cache or database have taken place. +** +** In rollback mode, a RESERVED or (if the transaction was opened with +** BEGIN EXCLUSIVE) EXCLUSIVE lock is obtained on the database file when +** moving to this state, but the journal file is not written to or opened +** to in this state. If the transaction is committed or rolled back while +** in WRITER_LOCKED state, all that is required is to unlock the database +** file. +** +** IN WAL mode, WalBeginWriteTransaction() is called to lock the log file. +** If the connection is running with locking_mode=exclusive, an attempt +** is made to obtain an EXCLUSIVE lock on the database file. +** +** * A write transaction is active. +** * If the connection is open in rollback-mode, a RESERVED or greater +** lock is held on the database file. +** * If the connection is open in WAL-mode, a WAL write transaction +** is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully +** called). +** * The dbSize, dbOrigSize and dbFileSize variables are all valid. +** * The contents of the pager cache have not been modified. +** * The journal file may or may not be open. +** * Nothing (not even the first header) has been written to the journal. +** +** WRITER_CACHEMOD: +** +** A pager moves from WRITER_LOCKED state to this state when a page is +** first modified by the upper layer. In rollback mode the journal file +** is opened (if it is not already open) and a header written to the +** start of it. The database file on disk has not been modified. +** +** * A write transaction is active. +** * A RESERVED or greater lock is held on the database file. +** * The journal file is open and the first header has been written +** to it, but the header has not been synced to disk. +** * The contents of the page cache have been modified. +** +** WRITER_DBMOD: +** +** The pager transitions from WRITER_CACHEMOD into WRITER_DBMOD state +** when it modifies the contents of the database file. WAL connections +** never enter this state (since they do not modify the database file, +** just the log file). +** +** * A write transaction is active. +** * An EXCLUSIVE or greater lock is held on the database file. +** * The journal file is open and the first header has been written +** and synced to disk. +** * The contents of the page cache have been modified (and possibly +** written to disk). +** +** WRITER_FINISHED: +** +** It is not possible for a WAL connection to enter this state. +** +** A rollback-mode pager changes to WRITER_FINISHED state from WRITER_DBMOD +** state after the entire transaction has been successfully written into the +** database file. In this state the transaction may be committed simply +** by finalizing the journal file. Once in WRITER_FINISHED state, it is +** not possible to modify the database further. At this point, the upper +** layer must either commit or rollback the transaction. +** +** * A write transaction is active. +** * An EXCLUSIVE or greater lock is held on the database file. +** * All writing and syncing of journal and database data has finished. +** If no error occurred, all that remains is to finalize the journal to +** commit the transaction. If an error did occur, the caller will need +** to rollback the transaction. +** +** ERROR: +** +** The ERROR state is entered when an IO or disk-full error (including +** SQLITE_IOERR_NOMEM) occurs at a point in the code that makes it +** difficult to be sure that the in-memory pager state (cache contents, +** db size etc.) are consistent with the contents of the file-system. +** +** Temporary pager files may enter the ERROR state, but in-memory pagers +** cannot. +** +** For example, if an IO error occurs while performing a rollback, +** the contents of the page-cache may be left in an inconsistent state. +** At this point it would be dangerous to change back to READER state +** (as usually happens after a rollback). Any subsequent readers might +** report database corruption (due to the inconsistent cache), and if +** they upgrade to writers, they may inadvertently corrupt the database +** file. To avoid this hazard, the pager switches into the ERROR state +** instead of READER following such an error. +** +** Once it has entered the ERROR state, any attempt to use the pager +** to read or write data returns an error. Eventually, once all +** outstanding transactions have been abandoned, the pager is able to +** transition back to OPEN state, discarding the contents of the +** page-cache and any other in-memory state at the same time. Everything +** is reloaded from disk (and, if necessary, hot-journal rollback performed) +** when a read-transaction is next opened on the pager (transitioning +** the pager into READER state). At that point the system has recovered +** from the error. +** +** Specifically, the pager jumps into the ERROR state if: +** +** 1. An error occurs while attempting a rollback. This happens in +** function sqlite3PagerRollback(). +** +** 2. An error occurs while attempting to finalize a journal file +** following a commit in function sqlite3PagerCommitPhaseTwo(). +** +** 3. An error occurs while attempting to write to the journal or +** database file in function pagerStress() in order to free up +** memory. +** +** In other cases, the error is returned to the b-tree layer. The b-tree +** layer then attempts a rollback operation. If the error condition +** persists, the pager enters the ERROR state via condition (1) above. +** +** Condition (3) is necessary because it can be triggered by a read-only +** statement executed within a transaction. In this case, if the error +** code were simply returned to the user, the b-tree layer would not +** automatically attempt a rollback, as it assumes that an error in a +** read-only statement cannot leave the pager in an internally inconsistent +** state. +** +** * The Pager.errCode variable is set to something other than SQLITE_OK. +** * There are one or more outstanding references to pages (after the +** last reference is dropped the pager should move back to OPEN state). +** * The pager is not an in-memory pager. +** +** +** Notes: +** +** * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the +** connection is open in WAL mode. A WAL connection is always in one +** of the first four states. +** +** * Normally, a connection open in exclusive mode is never in PAGER_OPEN +** state. There are two exceptions: immediately after exclusive-mode has +** been turned on (and before any read or write transactions are +** executed), and when the pager is leaving the "error state". +** +** * See also: assert_pager_state(). +*/ +#define PAGER_OPEN 0 +#define PAGER_READER 1 +#define PAGER_WRITER_LOCKED 2 +#define PAGER_WRITER_CACHEMOD 3 +#define PAGER_WRITER_DBMOD 4 +#define PAGER_WRITER_FINISHED 5 +#define PAGER_ERROR 6 + +/* +** The Pager.eLock variable is almost always set to one of the +** following locking-states, according to the lock currently held on +** the database file: NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK. +** This variable is kept up to date as locks are taken and released by +** the pagerLockDb() and pagerUnlockDb() wrappers. +** +** If the VFS xLock() or xUnlock() returns an error other than SQLITE_BUSY +** (i.e. one of the SQLITE_IOERR subtypes), it is not clear whether or not +** the operation was successful. In these circumstances pagerLockDb() and +** pagerUnlockDb() take a conservative approach - eLock is always updated +** when unlocking the file, and only updated when locking the file if the +** VFS call is successful. This way, the Pager.eLock variable may be set +** to a less exclusive (lower) value than the lock that is actually held +** at the system level, but it is never set to a more exclusive value. +** +** This is usually safe. If an xUnlock fails or appears to fail, there may +** be a few redundant xLock() calls or a lock may be held for longer than +** required, but nothing really goes wrong. +** +** The exception is when the database file is unlocked as the pager moves +** from ERROR to OPEN state. At this point there may be a hot-journal file +** in the file-system that needs to be rolled back (as part of an OPEN->SHARED +** transition, by the same pager or any other). If the call to xUnlock() +** fails at this point and the pager is left holding an EXCLUSIVE lock, this +** can confuse the call to xCheckReservedLock() call made later as part +** of hot-journal detection. +** +** xCheckReservedLock() is defined as returning true "if there is a RESERVED +** lock held by this process or any others". So xCheckReservedLock may +** return true because the caller itself is holding an EXCLUSIVE lock (but +** doesn't know it because of a previous error in xUnlock). If this happens +** a hot-journal may be mistaken for a journal being created by an active +** transaction in another process, causing SQLite to read from the database +** without rolling it back. +** +** To work around this, if a call to xUnlock() fails when unlocking the +** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It +** is only changed back to a real locking state after a successful call +** to xLock(EXCLUSIVE). Also, the code to do the OPEN->SHARED state transition +** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK +** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE +** lock on the database file before attempting to roll it back. See function +** PagerSharedLock() for more detail. +** +** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in +** PAGER_OPEN state. +*/ +#define UNKNOWN_LOCK (EXCLUSIVE_LOCK+1) + +/* +** The maximum allowed sector size. 64KiB. If the xSectorsize() method +** returns a value larger than this, then MAX_SECTOR_SIZE is used instead. +** This could conceivably cause corruption following a power failure on +** such a system. This is currently an undocumented limit. +*/ +#define MAX_SECTOR_SIZE 0x10000 + + +/* +** An instance of the following structure is allocated for each active +** savepoint and statement transaction in the system. All such structures +** are stored in the Pager.aSavepoint[] array, which is allocated and +** resized using sqlite3Realloc(). +** +** When a savepoint is created, the PagerSavepoint.iHdrOffset field is +** set to 0. If a journal-header is written into the main journal while +** the savepoint is active, then iHdrOffset is set to the byte offset +** immediately following the last journal record written into the main +** journal before the journal-header. This is required during savepoint +** rollback (see pagerPlaybackSavepoint()). +*/ +typedef struct PagerSavepoint PagerSavepoint; +struct PagerSavepoint { + i64 iOffset; /* Starting offset in main journal */ + i64 iHdrOffset; /* See above */ + Bitvec *pInSavepoint; /* Set of pages in this savepoint */ + Pgno nOrig; /* Original number of pages in file */ + Pgno iSubRec; /* Index of first record in sub-journal */ + int bTruncateOnRelease; /* If stmt journal may be truncated on RELEASE */ +#ifndef SQLITE_OMIT_WAL + u32 aWalData[WAL_SAVEPOINT_NDATA]; /* WAL savepoint context */ +#endif +}; + +/* +** Bits of the Pager.doNotSpill flag. See further description below. +*/ +#define SPILLFLAG_OFF 0x01 /* Never spill cache. Set via pragma */ +#define SPILLFLAG_ROLLBACK 0x02 /* Current rolling back, so do not spill */ +#define SPILLFLAG_NOSYNC 0x04 /* Spill is ok, but do not sync */ + +/* +** An open page cache is an instance of struct Pager. A description of +** some of the more important member variables follows: +** +** eState +** +** The current 'state' of the pager object. See the comment and state +** diagram above for a description of the pager state. +** +** eLock +** +** For a real on-disk database, the current lock held on the database file - +** NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK. +** +** For a temporary or in-memory database (neither of which require any +** locks), this variable is always set to EXCLUSIVE_LOCK. Since such +** databases always have Pager.exclusiveMode==1, this tricks the pager +** logic into thinking that it already has all the locks it will ever +** need (and no reason to release them). +** +** In some (obscure) circumstances, this variable may also be set to +** UNKNOWN_LOCK. See the comment above the #define of UNKNOWN_LOCK for +** details. +** +** changeCountDone +** +** This boolean variable is used to make sure that the change-counter +** (the 4-byte header field at byte offset 24 of the database file) is +** not updated more often than necessary. +** +** It is set to true when the change-counter field is updated, which +** can only happen if an exclusive lock is held on the database file. +** It is cleared (set to false) whenever an exclusive lock is +** relinquished on the database file. Each time a transaction is committed, +** The changeCountDone flag is inspected. If it is true, the work of +** updating the change-counter is omitted for the current transaction. +** +** This mechanism means that when running in exclusive mode, a connection +** need only update the change-counter once, for the first transaction +** committed. +** +** setSuper +** +** When PagerCommitPhaseOne() is called to commit a transaction, it may +** (or may not) specify a super-journal name to be written into the +** journal file before it is synced to disk. +** +** Whether or not a journal file contains a super-journal pointer affects +** the way in which the journal file is finalized after the transaction is +** committed or rolled back when running in "journal_mode=PERSIST" mode. +** If a journal file does not contain a super-journal pointer, it is +** finalized by overwriting the first journal header with zeroes. If +** it does contain a super-journal pointer the journal file is finalized +** by truncating it to zero bytes, just as if the connection were +** running in "journal_mode=truncate" mode. +** +** Journal files that contain super-journal pointers cannot be finalized +** simply by overwriting the first journal-header with zeroes, as the +** super-journal pointer could interfere with hot-journal rollback of any +** subsequently interrupted transaction that reuses the journal file. +** +** The flag is cleared as soon as the journal file is finalized (either +** by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the +** journal file from being successfully finalized, the setSuper flag +** is cleared anyway (and the pager will move to ERROR state). +** +** doNotSpill +** +** This variables control the behavior of cache-spills (calls made by +** the pcache module to the pagerStress() routine to write cached data +** to the file-system in order to free up memory). +** +** When bits SPILLFLAG_OFF or SPILLFLAG_ROLLBACK of doNotSpill are set, +** writing to the database from pagerStress() is disabled altogether. +** The SPILLFLAG_ROLLBACK case is done in a very obscure case that +** comes up during savepoint rollback that requires the pcache module +** to allocate a new page to prevent the journal file from being written +** while it is being traversed by code in pager_playback(). The SPILLFLAG_OFF +** case is a user preference. +** +** If the SPILLFLAG_NOSYNC bit is set, writing to the database from +** pagerStress() is permitted, but syncing the journal file is not. +** This flag is set by sqlite3PagerWrite() when the file-system sector-size +** is larger than the database page-size in order to prevent a journal sync +** from happening in between the journalling of two pages on the same sector. +** +** subjInMemory +** +** This is a boolean variable. If true, then any required sub-journal +** is opened as an in-memory journal file. If false, then in-memory +** sub-journals are only used for in-memory pager files. +** +** This variable is updated by the upper layer each time a new +** write-transaction is opened. +** +** dbSize, dbOrigSize, dbFileSize +** +** Variable dbSize is set to the number of pages in the database file. +** It is valid in PAGER_READER and higher states (all states except for +** OPEN and ERROR). +** +** dbSize is set based on the size of the database file, which may be +** larger than the size of the database (the value stored at offset +** 28 of the database header by the btree). If the size of the file +** is not an integer multiple of the page-size, the value stored in +** dbSize is rounded down (i.e. a 5KB file with 2K page-size has dbSize==2). +** Except, any file that is greater than 0 bytes in size is considered +** to have at least one page. (i.e. a 1KB file with 2K page-size leads +** to dbSize==1). +** +** During a write-transaction, if pages with page-numbers greater than +** dbSize are modified in the cache, dbSize is updated accordingly. +** Similarly, if the database is truncated using PagerTruncateImage(), +** dbSize is updated. +** +** Variables dbOrigSize and dbFileSize are valid in states +** PAGER_WRITER_LOCKED and higher. dbOrigSize is a copy of the dbSize +** variable at the start of the transaction. It is used during rollback, +** and to determine whether or not pages need to be journalled before +** being modified. +** +** Throughout a write-transaction, dbFileSize contains the size of +** the file on disk in pages. It is set to a copy of dbSize when the +** write-transaction is first opened, and updated when VFS calls are made +** to write or truncate the database file on disk. +** +** The only reason the dbFileSize variable is required is to suppress +** unnecessary calls to xTruncate() after committing a transaction. If, +** when a transaction is committed, the dbFileSize variable indicates +** that the database file is larger than the database image (Pager.dbSize), +** pager_truncate() is called. The pager_truncate() call uses xFilesize() +** to measure the database file on disk, and then truncates it if required. +** dbFileSize is not used when rolling back a transaction. In this case +** pager_truncate() is called unconditionally (which means there may be +** a call to xFilesize() that is not strictly required). In either case, +** pager_truncate() may cause the file to become smaller or larger. +** +** dbHintSize +** +** The dbHintSize variable is used to limit the number of calls made to +** the VFS xFileControl(FCNTL_SIZE_HINT) method. +** +** dbHintSize is set to a copy of the dbSize variable when a +** write-transaction is opened (at the same time as dbFileSize and +** dbOrigSize). If the xFileControl(FCNTL_SIZE_HINT) method is called, +** dbHintSize is increased to the number of pages that correspond to the +** size-hint passed to the method call. See pager_write_pagelist() for +** details. +** +** errCode +** +** The Pager.errCode variable is only ever used in PAGER_ERROR state. It +** is set to zero in all other states. In PAGER_ERROR state, Pager.errCode +** is always set to SQLITE_FULL, SQLITE_IOERR or one of the SQLITE_IOERR_XXX +** sub-codes. +** +** syncFlags, walSyncFlags +** +** syncFlags is either SQLITE_SYNC_NORMAL (0x02) or SQLITE_SYNC_FULL (0x03). +** syncFlags is used for rollback mode. walSyncFlags is used for WAL mode +** and contains the flags used to sync the checkpoint operations in the +** lower two bits, and sync flags used for transaction commits in the WAL +** file in bits 0x04 and 0x08. In other words, to get the correct sync flags +** for checkpoint operations, use (walSyncFlags&0x03) and to get the correct +** sync flags for transaction commit, use ((walSyncFlags>>2)&0x03). Note +** that with synchronous=NORMAL in WAL mode, transaction commit is not synced +** meaning that the 0x04 and 0x08 bits are both zero. +*/ +struct Pager { + sqlite3_vfs *pVfs; /* OS functions to use for IO */ + u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */ + u8 journalMode; /* One of the PAGER_JOURNALMODE_* values */ + u8 useJournal; /* Use a rollback journal on this file */ + u8 noSync; /* Do not sync the journal if true */ + u8 fullSync; /* Do extra syncs of the journal for robustness */ + u8 extraSync; /* sync directory after journal delete */ + u8 syncFlags; /* SYNC_NORMAL or SYNC_FULL otherwise */ + u8 walSyncFlags; /* See description above */ + u8 tempFile; /* zFilename is a temporary or immutable file */ + u8 noLock; /* Do not lock (except in WAL mode) */ + u8 readOnly; /* True for a read-only database */ + u8 memDb; /* True to inhibit all file I/O */ + u8 memVfs; /* VFS-implemented memory database */ + + /************************************************************************** + ** The following block contains those class members that change during + ** routine operation. Class members not in this block are either fixed + ** when the pager is first created or else only change when there is a + ** significant mode change (such as changing the page_size, locking_mode, + ** or the journal_mode). From another view, these class members describe + ** the "state" of the pager, while other class members describe the + ** "configuration" of the pager. + */ + u8 eState; /* Pager state (OPEN, READER, WRITER_LOCKED..) */ + u8 eLock; /* Current lock held on database file */ + u8 changeCountDone; /* Set after incrementing the change-counter */ + u8 setSuper; /* Super-jrnl name is written into jrnl */ + u8 doNotSpill; /* Do not spill the cache when non-zero */ + u8 subjInMemory; /* True to use in-memory sub-journals */ + u8 bUseFetch; /* True to use xFetch() */ + u8 hasHeldSharedLock; /* True if a shared lock has ever been held */ + Pgno dbSize; /* Number of pages in the database */ + Pgno dbOrigSize; /* dbSize before the current transaction */ + Pgno dbFileSize; /* Number of pages in the database file */ + Pgno dbHintSize; /* Value passed to FCNTL_SIZE_HINT call */ + int errCode; /* One of several kinds of errors */ + int nRec; /* Pages journalled since last j-header written */ + u32 cksumInit; /* Quasi-random value added to every checksum */ + u32 nSubRec; /* Number of records written to sub-journal */ + Bitvec *pInJournal; /* One bit for each page in the database file */ + sqlite3_file *fd; /* File descriptor for database */ + sqlite3_file *jfd; /* File descriptor for main journal */ + sqlite3_file *sjfd; /* File descriptor for sub-journal */ + i64 journalOff; /* Current write offset in the journal file */ + i64 journalHdr; /* Byte offset to previous journal header */ + sqlite3_backup *pBackup; /* Pointer to list of ongoing backup processes */ + PagerSavepoint *aSavepoint; /* Array of active savepoints */ + int nSavepoint; /* Number of elements in aSavepoint[] */ + u32 iDataVersion; /* Changes whenever database content changes */ + char dbFileVers[16]; /* Changes whenever database file changes */ + + int nMmapOut; /* Number of mmap pages currently outstanding */ + sqlite3_int64 szMmap; /* Desired maximum mmap size */ + PgHdr *pMmapFreelist; /* List of free mmap page headers (pDirty) */ + /* + ** End of the routinely-changing class members + ***************************************************************************/ + + u16 nExtra; /* Add this many bytes to each in-memory page */ + i16 nReserve; /* Number of unused bytes at end of each page */ + u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */ + u32 sectorSize; /* Assumed sector size during rollback */ + Pgno mxPgno; /* Maximum allowed size of the database */ + Pgno lckPgno; /* Page number for the locking page */ + i64 pageSize; /* Number of bytes in a page */ + i64 journalSizeLimit; /* Size limit for persistent journal files */ + char *zFilename; /* Name of the database file */ + char *zJournal; /* Name of the journal file */ + int (*xBusyHandler)(void*); /* Function to call when busy */ + void *pBusyHandlerArg; /* Context argument for xBusyHandler */ + u32 aStat[4]; /* Total cache hits, misses, writes, spills */ +#ifdef SQLITE_TEST + int nRead; /* Database pages read */ +#endif + void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */ + int (*xGet)(Pager*,Pgno,DbPage**,int); /* Routine to fetch a patch */ + char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */ + PCache *pPCache; /* Pointer to page cache object */ +#ifndef SQLITE_OMIT_WAL + Wal *pWal; /* Write-ahead log used by "journal_mode=wal" */ + char *zWal; /* File name for write-ahead log */ +#endif +}; + +/* +** Indexes for use with Pager.aStat[]. The Pager.aStat[] array contains +** the values accessed by passing SQLITE_DBSTATUS_CACHE_HIT, CACHE_MISS +** or CACHE_WRITE to sqlite3_db_status(). +*/ +#define PAGER_STAT_HIT 0 +#define PAGER_STAT_MISS 1 +#define PAGER_STAT_WRITE 2 +#define PAGER_STAT_SPILL 3 + +/* +** The following global variables hold counters used for +** testing purposes only. These variables do not exist in +** a non-testing build. These variables are not thread-safe. +*/ +#ifdef SQLITE_TEST +int sqlite3_pager_readdb_count = 0; /* Number of full pages read from DB */ +int sqlite3_pager_writedb_count = 0; /* Number of full pages written to DB */ +int sqlite3_pager_writej_count = 0; /* Number of pages written to journal */ +# define PAGER_INCR(v) v++ +#else +# define PAGER_INCR(v) +#endif + + + +/* +** Journal files begin with the following magic string. The data +** was obtained from /dev/random. It is used only as a sanity check. +** +** Since version 2.8.0, the journal format contains additional sanity +** checking information. If the power fails while the journal is being +** written, semi-random garbage data might appear in the journal +** file after power is restored. If an attempt is then made +** to roll the journal back, the database could be corrupted. The additional +** sanity checking data is an attempt to discover the garbage in the +** journal and ignore it. +** +** The sanity checking information for the new journal format consists +** of a 32-bit checksum on each page of data. The checksum covers both +** the page number and the pPager->pageSize bytes of data for the page. +** This cksum is initialized to a 32-bit random value that appears in the +** journal file right after the header. The random initializer is important, +** because garbage data that appears at the end of a journal is likely +** data that was once in other files that have now been deleted. If the +** garbage data came from an obsolete journal file, the checksums might +** be correct. But by initializing the checksum to random value which +** is different for every journal, we minimize that risk. +*/ +static const unsigned char aJournalMagic[] = { + 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7, +}; + +/* +** The size of the of each page record in the journal is given by +** the following macro. +*/ +#define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8) + +/* +** The journal header size for this pager. This is usually the same +** size as a single disk sector. See also setSectorSize(). +*/ +#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize) + +/* +** The macro MEMDB is true if we are dealing with an in-memory database. +** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set, +** the value of MEMDB will be a constant and the compiler will optimize +** out code that would never execute. +*/ +#ifdef SQLITE_OMIT_MEMORYDB +# define MEMDB 0 +#else +# define MEMDB pPager->memDb +#endif + +/* +** The macro USEFETCH is true if we are allowed to use the xFetch and xUnfetch +** interfaces to access the database using memory-mapped I/O. +*/ +#if SQLITE_MAX_MMAP_SIZE>0 +# define USEFETCH(x) ((x)->bUseFetch) +#else +# define USEFETCH(x) 0 +#endif + +/* +** The argument to this macro is a file descriptor (type sqlite3_file*). +** Return 0 if it is not open, or non-zero (but not 1) if it is. +** +** This is so that expressions can be written as: +** +** if( isOpen(pPager->jfd) ){ ... +** +** instead of +** +** if( pPager->jfd->pMethods ){ ... +*/ +#define isOpen(pFd) ((pFd)->pMethods!=0) + +#ifdef SQLITE_DIRECT_OVERFLOW_READ +/* +** Return true if page pgno can be read directly from the database file +** by the b-tree layer. This is the case if: +** +** * the database file is open, +** * there are no dirty pages in the cache, and +** * the desired page is not currently in the wal file. +*/ +int sqlite3PagerDirectReadOk(Pager *pPager, Pgno pgno){ + if( pPager->fd->pMethods==0 ) return 0; + if( sqlite3PCacheIsDirty(pPager->pPCache) ) return 0; +#ifndef SQLITE_OMIT_WAL + if( pPager->pWal ){ + u32 iRead = 0; + (void)sqlite3WalFindFrame(pPager->pWal, pgno, &iRead); + return iRead==0; + } +#endif + return 1; +} +#endif + +#ifndef SQLITE_OMIT_WAL +# define pagerUseWal(x) ((x)->pWal!=0) +#else +# define pagerUseWal(x) 0 +# define pagerRollbackWal(x) 0 +# define pagerWalFrames(v,w,x,y) 0 +# define pagerOpenWalIfPresent(z) SQLITE_OK +# define pagerBeginReadTransaction(z) SQLITE_OK +#endif + +#ifndef NDEBUG +/* +** Usage: +** +** assert( assert_pager_state(pPager) ); +** +** This function runs many asserts to try to find inconsistencies in +** the internal state of the Pager object. +*/ +static int assert_pager_state(Pager *p){ + Pager *pPager = p; + + /* State must be valid. */ + assert( p->eState==PAGER_OPEN + || p->eState==PAGER_READER + || p->eState==PAGER_WRITER_LOCKED + || p->eState==PAGER_WRITER_CACHEMOD + || p->eState==PAGER_WRITER_DBMOD + || p->eState==PAGER_WRITER_FINISHED + || p->eState==PAGER_ERROR + ); + + /* Regardless of the current state, a temp-file connection always behaves + ** as if it has an exclusive lock on the database file. It never updates + ** the change-counter field, so the changeCountDone flag is always set. + */ + assert( p->tempFile==0 || p->eLock==EXCLUSIVE_LOCK ); + assert( p->tempFile==0 || pPager->changeCountDone ); + + /* If the useJournal flag is clear, the journal-mode must be "OFF". + ** And if the journal-mode is "OFF", the journal file must not be open. + */ + assert( p->journalMode==PAGER_JOURNALMODE_OFF || p->useJournal ); + assert( p->journalMode!=PAGER_JOURNALMODE_OFF || !isOpen(p->jfd) ); + + /* Check that MEMDB implies noSync. And an in-memory journal. Since + ** this means an in-memory pager performs no IO at all, it cannot encounter + ** either SQLITE_IOERR or SQLITE_FULL during rollback or while finalizing + ** a journal file. (although the in-memory journal implementation may + ** return SQLITE_IOERR_NOMEM while the journal file is being written). It + ** is therefore not possible for an in-memory pager to enter the ERROR + ** state. + */ + if( MEMDB ){ + assert( !isOpen(p->fd) ); + assert( p->noSync ); + assert( p->journalMode==PAGER_JOURNALMODE_OFF + || p->journalMode==PAGER_JOURNALMODE_MEMORY + ); + assert( p->eState!=PAGER_ERROR && p->eState!=PAGER_OPEN ); + assert( pagerUseWal(p)==0 ); + } + + /* If changeCountDone is set, a RESERVED lock or greater must be held + ** on the file. + */ + assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK ); + assert( p->eLock!=PENDING_LOCK ); + + switch( p->eState ){ + case PAGER_OPEN: + assert( !MEMDB ); + assert( pPager->errCode==SQLITE_OK ); + assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile ); + break; + + case PAGER_READER: + assert( pPager->errCode==SQLITE_OK ); + assert( p->eLock!=UNKNOWN_LOCK ); + assert( p->eLock>=SHARED_LOCK ); + break; + + case PAGER_WRITER_LOCKED: + assert( p->eLock!=UNKNOWN_LOCK ); + assert( pPager->errCode==SQLITE_OK ); + if( !pagerUseWal(pPager) ){ + assert( p->eLock>=RESERVED_LOCK ); + } + assert( pPager->dbSize==pPager->dbOrigSize ); + assert( pPager->dbOrigSize==pPager->dbFileSize ); + assert( pPager->dbOrigSize==pPager->dbHintSize ); + assert( pPager->setSuper==0 ); + break; + + case PAGER_WRITER_CACHEMOD: + assert( p->eLock!=UNKNOWN_LOCK ); + assert( pPager->errCode==SQLITE_OK ); + if( !pagerUseWal(pPager) ){ + /* It is possible that if journal_mode=wal here that neither the + ** journal file nor the WAL file are open. This happens during + ** a rollback transaction that switches from journal_mode=off + ** to journal_mode=wal. + */ + assert( p->eLock>=RESERVED_LOCK ); + assert( isOpen(p->jfd) + || p->journalMode==PAGER_JOURNALMODE_OFF + || p->journalMode==PAGER_JOURNALMODE_WAL + ); + } + assert( pPager->dbOrigSize==pPager->dbFileSize ); + assert( pPager->dbOrigSize==pPager->dbHintSize ); + break; + + case PAGER_WRITER_DBMOD: + assert( p->eLock==EXCLUSIVE_LOCK ); + assert( pPager->errCode==SQLITE_OK ); + assert( !pagerUseWal(pPager) ); + assert( p->eLock>=EXCLUSIVE_LOCK ); + assert( isOpen(p->jfd) + || p->journalMode==PAGER_JOURNALMODE_OFF + || p->journalMode==PAGER_JOURNALMODE_WAL + || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC) + ); + assert( pPager->dbOrigSize<=pPager->dbHintSize ); + break; + + case PAGER_WRITER_FINISHED: + assert( p->eLock==EXCLUSIVE_LOCK ); + assert( pPager->errCode==SQLITE_OK ); + assert( !pagerUseWal(pPager) ); + assert( isOpen(p->jfd) + || p->journalMode==PAGER_JOURNALMODE_OFF + || p->journalMode==PAGER_JOURNALMODE_WAL + || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC) + ); + break; + + case PAGER_ERROR: + /* There must be at least one outstanding reference to the pager if + ** in ERROR state. Otherwise the pager should have already dropped + ** back to OPEN state. + */ + assert( pPager->errCode!=SQLITE_OK ); + assert( sqlite3PcacheRefCount(pPager->pPCache)>0 || pPager->tempFile ); + break; + } + + return 1; +} +#endif /* ifndef NDEBUG */ + +#ifdef SQLITE_DEBUG +/* +** Return a pointer to a human readable string in a static buffer +** containing the state of the Pager object passed as an argument. This +** is intended to be used within debuggers. For example, as an alternative +** to "print *pPager" in gdb: +** +** (gdb) printf "%s", print_pager_state(pPager) +** +** This routine has external linkage in order to suppress compiler warnings +** about an unused function. It is enclosed within SQLITE_DEBUG and so does +** not appear in normal builds. +*/ +char *print_pager_state(Pager *p){ + static char zRet[1024]; + + sqlite3_snprintf(1024, zRet, + "Filename: %s\n" + "State: %s errCode=%d\n" + "Lock: %s\n" + "Locking mode: locking_mode=%s\n" + "Journal mode: journal_mode=%s\n" + "Backing store: tempFile=%d memDb=%d useJournal=%d\n" + "Journal: journalOff=%lld journalHdr=%lld\n" + "Size: dbsize=%d dbOrigSize=%d dbFileSize=%d\n" + , p->zFilename + , p->eState==PAGER_OPEN ? "OPEN" : + p->eState==PAGER_READER ? "READER" : + p->eState==PAGER_WRITER_LOCKED ? "WRITER_LOCKED" : + p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" : + p->eState==PAGER_WRITER_DBMOD ? "WRITER_DBMOD" : + p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" : + p->eState==PAGER_ERROR ? "ERROR" : "?error?" + , (int)p->errCode + , p->eLock==NO_LOCK ? "NO_LOCK" : + p->eLock==RESERVED_LOCK ? "RESERVED" : + p->eLock==EXCLUSIVE_LOCK ? "EXCLUSIVE" : + p->eLock==SHARED_LOCK ? "SHARED" : + p->eLock==UNKNOWN_LOCK ? "UNKNOWN" : "?error?" + , p->exclusiveMode ? "exclusive" : "normal" + , p->journalMode==PAGER_JOURNALMODE_MEMORY ? "memory" : + p->journalMode==PAGER_JOURNALMODE_OFF ? "off" : + p->journalMode==PAGER_JOURNALMODE_DELETE ? "delete" : + p->journalMode==PAGER_JOURNALMODE_PERSIST ? "persist" : + p->journalMode==PAGER_JOURNALMODE_TRUNCATE ? "truncate" : + p->journalMode==PAGER_JOURNALMODE_WAL ? "wal" : "?error?" + , (int)p->tempFile, (int)p->memDb, (int)p->useJournal + , p->journalOff, p->journalHdr + , (int)p->dbSize, (int)p->dbOrigSize, (int)p->dbFileSize + ); + + return zRet; +} +#endif + +/* Forward references to the various page getters */ +static int getPageNormal(Pager*,Pgno,DbPage**,int); +static int getPageError(Pager*,Pgno,DbPage**,int); +#if SQLITE_MAX_MMAP_SIZE>0 +static int getPageMMap(Pager*,Pgno,DbPage**,int); +#endif + +/* +** Set the Pager.xGet method for the appropriate routine used to fetch +** content from the pager. +*/ +static void setGetterMethod(Pager *pPager){ + if( pPager->errCode ){ + pPager->xGet = getPageError; +#if SQLITE_MAX_MMAP_SIZE>0 + }else if( USEFETCH(pPager) ){ + pPager->xGet = getPageMMap; +#endif /* SQLITE_MAX_MMAP_SIZE>0 */ + }else{ + pPager->xGet = getPageNormal; + } +} + +/* +** Return true if it is necessary to write page *pPg into the sub-journal. +** A page needs to be written into the sub-journal if there exists one +** or more open savepoints for which: +** +** * The page-number is less than or equal to PagerSavepoint.nOrig, and +** * The bit corresponding to the page-number is not set in +** PagerSavepoint.pInSavepoint. +*/ +static int subjRequiresPage(PgHdr *pPg){ + Pager *pPager = pPg->pPager; + PagerSavepoint *p; + Pgno pgno = pPg->pgno; + int i; + for(i=0; i<pPager->nSavepoint; i++){ + p = &pPager->aSavepoint[i]; + if( p->nOrig>=pgno && 0==sqlite3BitvecTestNotNull(p->pInSavepoint, pgno) ){ + for(i=i+1; i<pPager->nSavepoint; i++){ + pPager->aSavepoint[i].bTruncateOnRelease = 0; + } + return 1; + } + } + return 0; +} + +#ifdef SQLITE_DEBUG +/* +** Return true if the page is already in the journal file. +*/ +static int pageInJournal(Pager *pPager, PgHdr *pPg){ + return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno); +} +#endif + +/* +** Read a 32-bit integer from the given file descriptor. Store the integer +** that is read in *pRes. Return SQLITE_OK if everything worked, or an +** error code is something goes wrong. +** +** All values are stored on disk as big-endian. +*/ +static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){ + unsigned char ac[4]; + int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset); + if( rc==SQLITE_OK ){ + *pRes = sqlite3Get4byte(ac); + } + return rc; +} + +/* +** Write a 32-bit integer into a string buffer in big-endian byte order. +*/ +#define put32bits(A,B) sqlite3Put4byte((u8*)A,B) + + +/* +** Write a 32-bit integer into the given file descriptor. Return SQLITE_OK +** on success or an error code is something goes wrong. +*/ +static int write32bits(sqlite3_file *fd, i64 offset, u32 val){ + char ac[4]; + put32bits(ac, val); + return sqlite3OsWrite(fd, ac, 4, offset); +} + +/* +** Unlock the database file to level eLock, which must be either NO_LOCK +** or SHARED_LOCK. Regardless of whether or not the call to xUnlock() +** succeeds, set the Pager.eLock variable to match the (attempted) new lock. +** +** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is +** called, do not modify it. See the comment above the #define of +** UNKNOWN_LOCK for an explanation of this. +*/ +static int pagerUnlockDb(Pager *pPager, int eLock){ + int rc = SQLITE_OK; + + assert( !pPager->exclusiveMode || pPager->eLock==eLock ); + assert( eLock==NO_LOCK || eLock==SHARED_LOCK ); + assert( eLock!=NO_LOCK || pagerUseWal(pPager)==0 ); + if( isOpen(pPager->fd) ){ + assert( pPager->eLock>=eLock ); + rc = pPager->noLock ? SQLITE_OK : sqlite3OsUnlock(pPager->fd, eLock); + if( pPager->eLock!=UNKNOWN_LOCK ){ + pPager->eLock = (u8)eLock; + } + IOTRACE(("UNLOCK %p %d\n", pPager, eLock)) + } + pPager->changeCountDone = pPager->tempFile; /* ticket fb3b3024ea238d5c */ + return rc; +} + +/* +** Lock the database file to level eLock, which must be either SHARED_LOCK, +** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the +** Pager.eLock variable to the new locking state. +** +** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is +** called, do not modify it unless the new locking state is EXCLUSIVE_LOCK. +** See the comment above the #define of UNKNOWN_LOCK for an explanation +** of this. +*/ +static int pagerLockDb(Pager *pPager, int eLock){ + int rc = SQLITE_OK; + + assert( eLock==SHARED_LOCK || eLock==RESERVED_LOCK || eLock==EXCLUSIVE_LOCK ); + if( pPager->eLock<eLock || pPager->eLock==UNKNOWN_LOCK ){ + rc = pPager->noLock ? SQLITE_OK : sqlite3OsLock(pPager->fd, eLock); + if( rc==SQLITE_OK && (pPager->eLock!=UNKNOWN_LOCK||eLock==EXCLUSIVE_LOCK) ){ + pPager->eLock = (u8)eLock; + IOTRACE(("LOCK %p %d\n", pPager, eLock)) + } + } + return rc; +} + +/* +** This function determines whether or not the atomic-write or +** atomic-batch-write optimizations can be used with this pager. The +** atomic-write optimization can be used if: +** +** (a) the value returned by OsDeviceCharacteristics() indicates that +** a database page may be written atomically, and +** (b) the value returned by OsSectorSize() is less than or equal +** to the page size. +** +** If it can be used, then the value returned is the size of the journal +** file when it contains rollback data for exactly one page. +** +** The atomic-batch-write optimization can be used if OsDeviceCharacteristics() +** returns a value with the SQLITE_IOCAP_BATCH_ATOMIC bit set. -1 is +** returned in this case. +** +** If neither optimization can be used, 0 is returned. +*/ +static int jrnlBufferSize(Pager *pPager){ + assert( !MEMDB ); + +#if defined(SQLITE_ENABLE_ATOMIC_WRITE) \ + || defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE) + int dc; /* Device characteristics */ + + assert( isOpen(pPager->fd) ); + dc = sqlite3OsDeviceCharacteristics(pPager->fd); +#else + UNUSED_PARAMETER(pPager); +#endif + +#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE + if( pPager->dbSize>0 && (dc&SQLITE_IOCAP_BATCH_ATOMIC) ){ + return -1; + } +#endif + +#ifdef SQLITE_ENABLE_ATOMIC_WRITE + { + int nSector = pPager->sectorSize; + int szPage = pPager->pageSize; + + assert(SQLITE_IOCAP_ATOMIC512==(512>>8)); + assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8)); + if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){ + return 0; + } + } + + return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager); +#endif + + return 0; +} + +/* +** If SQLITE_CHECK_PAGES is defined then we do some sanity checking +** on the cache using a hash function. This is used for testing +** and debugging only. +*/ +#ifdef SQLITE_CHECK_PAGES +/* +** Return a 32-bit hash of the page data for pPage. +*/ +static u32 pager_datahash(int nByte, unsigned char *pData){ + u32 hash = 0; + int i; + for(i=0; i<nByte; i++){ + hash = (hash*1039) + pData[i]; + } + return hash; +} +static u32 pager_pagehash(PgHdr *pPage){ + return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData); +} +static void pager_set_pagehash(PgHdr *pPage){ + pPage->pageHash = pager_pagehash(pPage); +} + +/* +** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES +** is defined, and NDEBUG is not defined, an assert() statement checks +** that the page is either dirty or still matches the calculated page-hash. +*/ +#define CHECK_PAGE(x) checkPage(x) +static void checkPage(PgHdr *pPg){ + Pager *pPager = pPg->pPager; + assert( pPager->eState!=PAGER_ERROR ); + assert( (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) ); +} + +#else +#define pager_datahash(X,Y) 0 +#define pager_pagehash(X) 0 +#define pager_set_pagehash(X) +#define CHECK_PAGE(x) +#endif /* SQLITE_CHECK_PAGES */ + +/* +** When this is called the journal file for pager pPager must be open. +** This function attempts to read a super-journal file name from the +** end of the file and, if successful, copies it into memory supplied +** by the caller. See comments above writeSuperJournal() for the format +** used to store a super-journal file name at the end of a journal file. +** +** zSuper must point to a buffer of at least nSuper bytes allocated by +** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is +** enough space to write the super-journal name). If the super-journal +** name in the journal is longer than nSuper bytes (including a +** nul-terminator), then this is handled as if no super-journal name +** were present in the journal. +** +** If a super-journal file name is present at the end of the journal +** file, then it is copied into the buffer pointed to by zSuper. A +** nul-terminator byte is appended to the buffer following the +** super-journal file name. +** +** If it is determined that no super-journal file name is present +** zSuper[0] is set to 0 and SQLITE_OK returned. +** +** If an error occurs while reading from the journal file, an SQLite +** error code is returned. +*/ +static int readSuperJournal(sqlite3_file *pJrnl, char *zSuper, u32 nSuper){ + int rc; /* Return code */ + u32 len; /* Length in bytes of super-journal name */ + i64 szJ; /* Total size in bytes of journal file pJrnl */ + u32 cksum; /* MJ checksum value read from journal */ + u32 u; /* Unsigned loop counter */ + unsigned char aMagic[8]; /* A buffer to hold the magic header */ + zSuper[0] = '\0'; + + if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ)) + || szJ<16 + || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len)) + || len>=nSuper + || len>szJ-16 + || len==0 + || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum)) + || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8)) + || memcmp(aMagic, aJournalMagic, 8) + || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zSuper, len, szJ-16-len)) + ){ + return rc; + } + + /* See if the checksum matches the super-journal name */ + for(u=0; u<len; u++){ + cksum -= zSuper[u]; + } + if( cksum ){ + /* If the checksum doesn't add up, then one or more of the disk sectors + ** containing the super-journal filename is corrupted. This means + ** definitely roll back, so just return SQLITE_OK and report a (nul) + ** super-journal filename. + */ + len = 0; + } + zSuper[len] = '\0'; + zSuper[len+1] = '\0'; + + return SQLITE_OK; +} + +/* +** Return the offset of the sector boundary at or immediately +** following the value in pPager->journalOff, assuming a sector +** size of pPager->sectorSize bytes. +** +** i.e for a sector size of 512: +** +** Pager.journalOff Return value +** --------------------------------------- +** 0 0 +** 512 512 +** 100 512 +** 2000 2048 +** +*/ +static i64 journalHdrOffset(Pager *pPager){ + i64 offset = 0; + i64 c = pPager->journalOff; + if( c ){ + offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager); + } + assert( offset%JOURNAL_HDR_SZ(pPager)==0 ); + assert( offset>=c ); + assert( (offset-c)<JOURNAL_HDR_SZ(pPager) ); + return offset; +} + +/* +** The journal file must be open when this function is called. +** +** This function is a no-op if the journal file has not been written to +** within the current transaction (i.e. if Pager.journalOff==0). +** +** If doTruncate is non-zero or the Pager.journalSizeLimit variable is +** set to 0, then truncate the journal file to zero bytes in size. Otherwise, +** zero the 28-byte header at the start of the journal file. In either case, +** if the pager is not in no-sync mode, sync the journal file immediately +** after writing or truncating it. +** +** If Pager.journalSizeLimit is set to a positive, non-zero value, and +** following the truncation or zeroing described above the size of the +** journal file in bytes is larger than this value, then truncate the +** journal file to Pager.journalSizeLimit bytes. The journal file does +** not need to be synced following this operation. +** +** If an IO error occurs, abandon processing and return the IO error code. +** Otherwise, return SQLITE_OK. +*/ +static int zeroJournalHdr(Pager *pPager, int doTruncate){ + int rc = SQLITE_OK; /* Return code */ + assert( isOpen(pPager->jfd) ); + assert( !sqlite3JournalIsInMemory(pPager->jfd) ); + if( pPager->journalOff ){ + const i64 iLimit = pPager->journalSizeLimit; /* Local cache of jsl */ + + IOTRACE(("JZEROHDR %p\n", pPager)) + if( doTruncate || iLimit==0 ){ + rc = sqlite3OsTruncate(pPager->jfd, 0); + }else{ + static const char zeroHdr[28] = {0}; + rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0); + } + if( rc==SQLITE_OK && !pPager->noSync ){ + rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->syncFlags); + } + + /* At this point the transaction is committed but the write lock + ** is still held on the file. If there is a size limit configured for + ** the persistent journal and the journal file currently consumes more + ** space than that limit allows for, truncate it now. There is no need + ** to sync the file following this operation. + */ + if( rc==SQLITE_OK && iLimit>0 ){ + i64 sz; + rc = sqlite3OsFileSize(pPager->jfd, &sz); + if( rc==SQLITE_OK && sz>iLimit ){ + rc = sqlite3OsTruncate(pPager->jfd, iLimit); + } + } + } + return rc; +} + +/* +** The journal file must be open when this routine is called. A journal +** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the +** current location. +** +** The format for the journal header is as follows: +** - 8 bytes: Magic identifying journal format. +** - 4 bytes: Number of records in journal, or -1 no-sync mode is on. +** - 4 bytes: Random number used for page hash. +** - 4 bytes: Initial database page count. +** - 4 bytes: Sector size used by the process that wrote this journal. +** - 4 bytes: Database page size. +** +** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space. +*/ +static int writeJournalHdr(Pager *pPager){ + int rc = SQLITE_OK; /* Return code */ + char *zHeader = pPager->pTmpSpace; /* Temporary space used to build header */ + u32 nHeader = (u32)pPager->pageSize;/* Size of buffer pointed to by zHeader */ + u32 nWrite; /* Bytes of header sector written */ + int ii; /* Loop counter */ + + assert( isOpen(pPager->jfd) ); /* Journal file must be open. */ + + if( nHeader>JOURNAL_HDR_SZ(pPager) ){ + nHeader = JOURNAL_HDR_SZ(pPager); + } + + /* If there are active savepoints and any of them were created + ** since the most recent journal header was written, update the + ** PagerSavepoint.iHdrOffset fields now. + */ + for(ii=0; ii<pPager->nSavepoint; ii++){ + if( pPager->aSavepoint[ii].iHdrOffset==0 ){ + pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff; + } + } + + pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager); + + /* + ** Write the nRec Field - the number of page records that follow this + ** journal header. Normally, zero is written to this value at this time. + ** After the records are added to the journal (and the journal synced, + ** if in full-sync mode), the zero is overwritten with the true number + ** of records (see syncJournal()). + ** + ** A faster alternative is to write 0xFFFFFFFF to the nRec field. When + ** reading the journal this value tells SQLite to assume that the + ** rest of the journal file contains valid page records. This assumption + ** is dangerous, as if a failure occurred whilst writing to the journal + ** file it may contain some garbage data. There are two scenarios + ** where this risk can be ignored: + ** + ** * When the pager is in no-sync mode. Corruption can follow a + ** power failure in this case anyway. + ** + ** * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees + ** that garbage data is never appended to the journal file. + */ + assert( isOpen(pPager->fd) || pPager->noSync ); + if( pPager->noSync || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY) + || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND) + ){ + memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic)); + put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff); + }else{ + memset(zHeader, 0, sizeof(aJournalMagic)+4); + } + + + + /* The random check-hash initializer */ + if( pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){ + sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit); + } +#ifdef SQLITE_DEBUG + else{ + /* The Pager.cksumInit variable is usually randomized above to protect + ** against there being existing records in the journal file. This is + ** dangerous, as following a crash they may be mistaken for records + ** written by the current transaction and rolled back into the database + ** file, causing corruption. The following assert statements verify + ** that this is not required in "journal_mode=memory" mode, as in that + ** case the journal file is always 0 bytes in size at this point. + ** It is advantageous to avoid the sqlite3_randomness() call if possible + ** as it takes the global PRNG mutex. */ + i64 sz = 0; + sqlite3OsFileSize(pPager->jfd, &sz); + assert( sz==0 ); + assert( pPager->journalOff==journalHdrOffset(pPager) ); + assert( sqlite3JournalIsInMemory(pPager->jfd) ); + } +#endif + put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit); + + /* The initial database size */ + put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize); + /* The assumed sector size for this process */ + put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize); + + /* The page size */ + put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize); + + /* Initializing the tail of the buffer is not necessary. Everything + ** works find if the following memset() is omitted. But initializing + ** the memory prevents valgrind from complaining, so we are willing to + ** take the performance hit. + */ + memset(&zHeader[sizeof(aJournalMagic)+20], 0, + nHeader-(sizeof(aJournalMagic)+20)); + + /* In theory, it is only necessary to write the 28 bytes that the + ** journal header consumes to the journal file here. Then increment the + ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next + ** record is written to the following sector (leaving a gap in the file + ** that will be implicitly filled in by the OS). + ** + ** However it has been discovered that on some systems this pattern can + ** be significantly slower than contiguously writing data to the file, + ** even if that means explicitly writing data to the block of + ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what + ** is done. + ** + ** The loop is required here in case the sector-size is larger than the + ** database page size. Since the zHeader buffer is only Pager.pageSize + ** bytes in size, more than one call to sqlite3OsWrite() may be required + ** to populate the entire journal header sector. + */ + for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){ + IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader)) + rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff); + assert( pPager->journalHdr <= pPager->journalOff ); + pPager->journalOff += nHeader; + } + + return rc; +} + +/* +** The journal file must be open when this is called. A journal header file +** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal +** file. The current location in the journal file is given by +** pPager->journalOff. See comments above function writeJournalHdr() for +** a description of the journal header format. +** +** If the header is read successfully, *pNRec is set to the number of +** page records following this header and *pDbSize is set to the size of the +** database before the transaction began, in pages. Also, pPager->cksumInit +** is set to the value read from the journal header. SQLITE_OK is returned +** in this case. +** +** If the journal header file appears to be corrupted, SQLITE_DONE is +** returned and *pNRec and *PDbSize are undefined. If JOURNAL_HDR_SZ bytes +** cannot be read from the journal file an error code is returned. +*/ +static int readJournalHdr( + Pager *pPager, /* Pager object */ + int isHot, + i64 journalSize, /* Size of the open journal file in bytes */ + u32 *pNRec, /* OUT: Value read from the nRec field */ + u32 *pDbSize /* OUT: Value of original database size field */ +){ + int rc; /* Return code */ + unsigned char aMagic[8]; /* A buffer to hold the magic header */ + i64 iHdrOff; /* Offset of journal header being read */ + + assert( isOpen(pPager->jfd) ); /* Journal file must be open. */ + + /* Advance Pager.journalOff to the start of the next sector. If the + ** journal file is too small for there to be a header stored at this + ** point, return SQLITE_DONE. + */ + pPager->journalOff = journalHdrOffset(pPager); + if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){ + return SQLITE_DONE; + } + iHdrOff = pPager->journalOff; + + /* Read in the first 8 bytes of the journal header. If they do not match + ** the magic string found at the start of each journal header, return + ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise, + ** proceed. + */ + if( isHot || iHdrOff!=pPager->journalHdr ){ + rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff); + if( rc ){ + return rc; + } + if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){ + return SQLITE_DONE; + } + } + + /* Read the first three 32-bit fields of the journal header: The nRec + ** field, the checksum-initializer and the database size at the start + ** of the transaction. Return an error code if anything goes wrong. + */ + if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec)) + || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit)) + || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize)) + ){ + return rc; + } + + if( pPager->journalOff==0 ){ + u32 iPageSize; /* Page-size field of journal header */ + u32 iSectorSize; /* Sector-size field of journal header */ + + /* Read the page-size and sector-size journal header fields. */ + if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize)) + || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize)) + ){ + return rc; + } + + /* Versions of SQLite prior to 3.5.8 set the page-size field of the + ** journal header to zero. In this case, assume that the Pager.pageSize + ** variable is already set to the correct page size. + */ + if( iPageSize==0 ){ + iPageSize = pPager->pageSize; + } + + /* Check that the values read from the page-size and sector-size fields + ** are within range. To be 'in range', both values need to be a power + ** of two greater than or equal to 512 or 32, and not greater than their + ** respective compile time maximum limits. + */ + if( iPageSize<512 || iSectorSize<32 + || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE + || ((iPageSize-1)&iPageSize)!=0 || ((iSectorSize-1)&iSectorSize)!=0 + ){ + /* If the either the page-size or sector-size in the journal-header is + ** invalid, then the process that wrote the journal-header must have + ** crashed before the header was synced. In this case stop reading + ** the journal file here. + */ + return SQLITE_DONE; + } + + /* Update the page-size to match the value read from the journal. + ** Use a testcase() macro to make sure that malloc failure within + ** PagerSetPagesize() is tested. + */ + rc = sqlite3PagerSetPagesize(pPager, &iPageSize, -1); + testcase( rc!=SQLITE_OK ); + + /* Update the assumed sector-size to match the value used by + ** the process that created this journal. If this journal was + ** created by a process other than this one, then this routine + ** is being called from within pager_playback(). The local value + ** of Pager.sectorSize is restored at the end of that routine. + */ + pPager->sectorSize = iSectorSize; + } + + pPager->journalOff += JOURNAL_HDR_SZ(pPager); + return rc; +} + + +/* +** Write the supplied super-journal name into the journal file for pager +** pPager at the current location. The super-journal name must be the last +** thing written to a journal file. If the pager is in full-sync mode, the +** journal file descriptor is advanced to the next sector boundary before +** anything is written. The format is: +** +** + 4 bytes: PAGER_SJ_PGNO. +** + N bytes: super-journal filename in utf-8. +** + 4 bytes: N (length of super-journal name in bytes, no nul-terminator). +** + 4 bytes: super-journal name checksum. +** + 8 bytes: aJournalMagic[]. +** +** The super-journal page checksum is the sum of the bytes in the super-journal +** name, where each byte is interpreted as a signed 8-bit integer. +** +** If zSuper is a NULL pointer (occurs for a single database transaction), +** this call is a no-op. +*/ +static int writeSuperJournal(Pager *pPager, const char *zSuper){ + int rc; /* Return code */ + int nSuper; /* Length of string zSuper */ + i64 iHdrOff; /* Offset of header in journal file */ + i64 jrnlSize; /* Size of journal file on disk */ + u32 cksum = 0; /* Checksum of string zSuper */ + + assert( pPager->setSuper==0 ); + assert( !pagerUseWal(pPager) ); + + if( !zSuper + || pPager->journalMode==PAGER_JOURNALMODE_MEMORY + || !isOpen(pPager->jfd) + ){ + return SQLITE_OK; + } + pPager->setSuper = 1; + assert( pPager->journalHdr <= pPager->journalOff ); + + /* Calculate the length in bytes and the checksum of zSuper */ + for(nSuper=0; zSuper[nSuper]; nSuper++){ + cksum += zSuper[nSuper]; + } + + /* If in full-sync mode, advance to the next disk sector before writing + ** the super-journal name. This is in case the previous page written to + ** the journal has already been synced. + */ + if( pPager->fullSync ){ + pPager->journalOff = journalHdrOffset(pPager); + } + iHdrOff = pPager->journalOff; + + /* Write the super-journal data to the end of the journal file. If + ** an error occurs, return the error code to the caller. + */ + if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_SJ_PGNO(pPager)))) + || (0 != (rc = sqlite3OsWrite(pPager->jfd, zSuper, nSuper, iHdrOff+4))) + || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper, nSuper))) + || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper+4, cksum))) + || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8, + iHdrOff+4+nSuper+8))) + ){ + return rc; + } + pPager->journalOff += (nSuper+20); + + /* If the pager is in persistent-journal mode, then the physical + ** journal-file may extend past the end of the super-journal name + ** and 8 bytes of magic data just written to the file. This is + ** dangerous because the code to rollback a hot-journal file + ** will not be able to find the super-journal name to determine + ** whether or not the journal is hot. + ** + ** Easiest thing to do in this scenario is to truncate the journal + ** file to the required size. + */ + if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize)) + && jrnlSize>pPager->journalOff + ){ + rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff); + } + return rc; +} + +/* +** Discard the entire contents of the in-memory page-cache. +*/ +static void pager_reset(Pager *pPager){ + pPager->iDataVersion++; + sqlite3BackupRestart(pPager->pBackup); + sqlite3PcacheClear(pPager->pPCache); +} + +/* +** Return the pPager->iDataVersion value +*/ +u32 sqlite3PagerDataVersion(Pager *pPager){ + return pPager->iDataVersion; +} + +/* +** Free all structures in the Pager.aSavepoint[] array and set both +** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal +** if it is open and the pager is not in exclusive mode. +*/ +static void releaseAllSavepoints(Pager *pPager){ + int ii; /* Iterator for looping through Pager.aSavepoint */ + for(ii=0; ii<pPager->nSavepoint; ii++){ + sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint); + } + if( !pPager->exclusiveMode || sqlite3JournalIsInMemory(pPager->sjfd) ){ + sqlite3OsClose(pPager->sjfd); + } + sqlite3_free(pPager->aSavepoint); + pPager->aSavepoint = 0; + pPager->nSavepoint = 0; + pPager->nSubRec = 0; +} + +/* +** Set the bit number pgno in the PagerSavepoint.pInSavepoint +** bitvecs of all open savepoints. Return SQLITE_OK if successful +** or SQLITE_NOMEM if a malloc failure occurs. +*/ +static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){ + int ii; /* Loop counter */ + int rc = SQLITE_OK; /* Result code */ + + for(ii=0; ii<pPager->nSavepoint; ii++){ + PagerSavepoint *p = &pPager->aSavepoint[ii]; + if( pgno<=p->nOrig ){ + rc |= sqlite3BitvecSet(p->pInSavepoint, pgno); + testcase( rc==SQLITE_NOMEM ); + assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); + } + } + return rc; +} + +/* +** This function is a no-op if the pager is in exclusive mode and not +** in the ERROR state. Otherwise, it switches the pager to PAGER_OPEN +** state. +** +** If the pager is not in exclusive-access mode, the database file is +** completely unlocked. If the file is unlocked and the file-system does +** not exhibit the UNDELETABLE_WHEN_OPEN property, the journal file is +** closed (if it is open). +** +** If the pager is in ERROR state when this function is called, the +** contents of the pager cache are discarded before switching back to +** the OPEN state. Regardless of whether the pager is in exclusive-mode +** or not, any journal file left in the file-system will be treated +** as a hot-journal and rolled back the next time a read-transaction +** is opened (by this or by any other connection). +*/ +static void pager_unlock(Pager *pPager){ + + assert( pPager->eState==PAGER_READER + || pPager->eState==PAGER_OPEN + || pPager->eState==PAGER_ERROR + ); + + sqlite3BitvecDestroy(pPager->pInJournal); + pPager->pInJournal = 0; + releaseAllSavepoints(pPager); + + if( pagerUseWal(pPager) ){ + assert( !isOpen(pPager->jfd) ); + sqlite3WalEndReadTransaction(pPager->pWal); + pPager->eState = PAGER_OPEN; + }else if( !pPager->exclusiveMode ){ + int rc; /* Error code returned by pagerUnlockDb() */ + int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0; + + /* If the operating system support deletion of open files, then + ** close the journal file when dropping the database lock. Otherwise + ** another connection with journal_mode=delete might delete the file + ** out from under us. + */ + assert( (PAGER_JOURNALMODE_MEMORY & 5)!=1 ); + assert( (PAGER_JOURNALMODE_OFF & 5)!=1 ); + assert( (PAGER_JOURNALMODE_WAL & 5)!=1 ); + assert( (PAGER_JOURNALMODE_DELETE & 5)!=1 ); + assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 ); + assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 ); + if( 0==(iDc & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN) + || 1!=(pPager->journalMode & 5) + ){ + sqlite3OsClose(pPager->jfd); + } + + /* If the pager is in the ERROR state and the call to unlock the database + ** file fails, set the current lock to UNKNOWN_LOCK. See the comment + ** above the #define for UNKNOWN_LOCK for an explanation of why this + ** is necessary. + */ + rc = pagerUnlockDb(pPager, NO_LOCK); + if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){ + pPager->eLock = UNKNOWN_LOCK; + } + + /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here + ** without clearing the error code. This is intentional - the error + ** code is cleared and the cache reset in the block below. + */ + assert( pPager->errCode || pPager->eState!=PAGER_ERROR ); + pPager->eState = PAGER_OPEN; + } + + /* If Pager.errCode is set, the contents of the pager cache cannot be + ** trusted. Now that there are no outstanding references to the pager, + ** it can safely move back to PAGER_OPEN state. This happens in both + ** normal and exclusive-locking mode. + */ + assert( pPager->errCode==SQLITE_OK || !MEMDB ); + if( pPager->errCode ){ + if( pPager->tempFile==0 ){ + pager_reset(pPager); + pPager->changeCountDone = 0; + pPager->eState = PAGER_OPEN; + }else{ + pPager->eState = (isOpen(pPager->jfd) ? PAGER_OPEN : PAGER_READER); + } + if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0); + pPager->errCode = SQLITE_OK; + setGetterMethod(pPager); + } + + pPager->journalOff = 0; + pPager->journalHdr = 0; + pPager->setSuper = 0; +} + +/* +** This function is called whenever an IOERR or FULL error that requires +** the pager to transition into the ERROR state may have occurred. +** The first argument is a pointer to the pager structure, the second +** the error-code about to be returned by a pager API function. The +** value returned is a copy of the second argument to this function. +** +** If the second argument is SQLITE_FULL, SQLITE_IOERR or one of the +** IOERR sub-codes, the pager enters the ERROR state and the error code +** is stored in Pager.errCode. While the pager remains in the ERROR state, +** all major API calls on the Pager will immediately return Pager.errCode. +** +** The ERROR state indicates that the contents of the pager-cache +** cannot be trusted. This state can be cleared by completely discarding +** the contents of the pager-cache. If a transaction was active when +** the persistent error occurred, then the rollback journal may need +** to be replayed to restore the contents of the database file (as if +** it were a hot-journal). +*/ +static int pager_error(Pager *pPager, int rc){ + int rc2 = rc & 0xff; + assert( rc==SQLITE_OK || !MEMDB ); + assert( + pPager->errCode==SQLITE_FULL || + pPager->errCode==SQLITE_OK || + (pPager->errCode & 0xff)==SQLITE_IOERR + ); + if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){ + pPager->errCode = rc; + pPager->eState = PAGER_ERROR; + setGetterMethod(pPager); + } + return rc; +} + +static int pager_truncate(Pager *pPager, Pgno nPage); + +/* +** The write transaction open on pPager is being committed (bCommit==1) +** or rolled back (bCommit==0). +** +** Return TRUE if and only if all dirty pages should be flushed to disk. +** +** Rules: +** +** * For non-TEMP databases, always sync to disk. This is necessary +** for transactions to be durable. +** +** * Sync TEMP database only on a COMMIT (not a ROLLBACK) when the backing +** file has been created already (via a spill on pagerStress()) and +** when the number of dirty pages in memory exceeds 25% of the total +** cache size. +*/ +static int pagerFlushOnCommit(Pager *pPager, int bCommit){ + if( pPager->tempFile==0 ) return 1; + if( !bCommit ) return 0; + if( !isOpen(pPager->fd) ) return 0; + return (sqlite3PCachePercentDirty(pPager->pPCache)>=25); +} + +/* +** This routine ends a transaction. A transaction is usually ended by +** either a COMMIT or a ROLLBACK operation. This routine may be called +** after rollback of a hot-journal, or if an error occurs while opening +** the journal file or writing the very first journal-header of a +** database transaction. +** +** This routine is never called in PAGER_ERROR state. If it is called +** in PAGER_NONE or PAGER_SHARED state and the lock held is less +** exclusive than a RESERVED lock, it is a no-op. +** +** Otherwise, any active savepoints are released. +** +** If the journal file is open, then it is "finalized". Once a journal +** file has been finalized it is not possible to use it to roll back a +** transaction. Nor will it be considered to be a hot-journal by this +** or any other database connection. Exactly how a journal is finalized +** depends on whether or not the pager is running in exclusive mode and +** the current journal-mode (Pager.journalMode value), as follows: +** +** journalMode==MEMORY +** Journal file descriptor is simply closed. This destroys an +** in-memory journal. +** +** journalMode==TRUNCATE +** Journal file is truncated to zero bytes in size. +** +** journalMode==PERSIST +** The first 28 bytes of the journal file are zeroed. This invalidates +** the first journal header in the file, and hence the entire journal +** file. An invalid journal file cannot be rolled back. +** +** journalMode==DELETE +** The journal file is closed and deleted using sqlite3OsDelete(). +** +** If the pager is running in exclusive mode, this method of finalizing +** the journal file is never used. Instead, if the journalMode is +** DELETE and the pager is in exclusive mode, the method described under +** journalMode==PERSIST is used instead. +** +** After the journal is finalized, the pager moves to PAGER_READER state. +** If running in non-exclusive rollback mode, the lock on the file is +** downgraded to a SHARED_LOCK. +** +** SQLITE_OK is returned if no error occurs. If an error occurs during +** any of the IO operations to finalize the journal file or unlock the +** database then the IO error code is returned to the user. If the +** operation to finalize the journal file fails, then the code still +** tries to unlock the database file if not in exclusive mode. If the +** unlock operation fails as well, then the first error code related +** to the first error encountered (the journal finalization one) is +** returned. +*/ +static int pager_end_transaction(Pager *pPager, int hasSuper, int bCommit){ + int rc = SQLITE_OK; /* Error code from journal finalization operation */ + int rc2 = SQLITE_OK; /* Error code from db file unlock operation */ + + /* Do nothing if the pager does not have an open write transaction + ** or at least a RESERVED lock. This function may be called when there + ** is no write-transaction active but a RESERVED or greater lock is + ** held under two circumstances: + ** + ** 1. After a successful hot-journal rollback, it is called with + ** eState==PAGER_NONE and eLock==EXCLUSIVE_LOCK. + ** + ** 2. If a connection with locking_mode=exclusive holding an EXCLUSIVE + ** lock switches back to locking_mode=normal and then executes a + ** read-transaction, this function is called with eState==PAGER_READER + ** and eLock==EXCLUSIVE_LOCK when the read-transaction is closed. + */ + assert( assert_pager_state(pPager) ); + assert( pPager->eState!=PAGER_ERROR ); + if( pPager->eState<PAGER_WRITER_LOCKED && pPager->eLock<RESERVED_LOCK ){ + return SQLITE_OK; + } + + releaseAllSavepoints(pPager); + assert( isOpen(pPager->jfd) || pPager->pInJournal==0 + || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_BATCH_ATOMIC) + ); + if( isOpen(pPager->jfd) ){ + assert( !pagerUseWal(pPager) ); + + /* Finalize the journal file. */ + if( sqlite3JournalIsInMemory(pPager->jfd) ){ + /* assert( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ); */ + sqlite3OsClose(pPager->jfd); + }else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){ + if( pPager->journalOff==0 ){ + rc = SQLITE_OK; + }else{ + rc = sqlite3OsTruncate(pPager->jfd, 0); + if( rc==SQLITE_OK && pPager->fullSync ){ + /* Make sure the new file size is written into the inode right away. + ** Otherwise the journal might resurrect following a power loss and + ** cause the last transaction to roll back. See + ** https://bugzilla.mozilla.org/show_bug.cgi?id=1072773 + */ + rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags); + } + } + pPager->journalOff = 0; + }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST + || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL) + ){ + rc = zeroJournalHdr(pPager, hasSuper||pPager->tempFile); + pPager->journalOff = 0; + }else{ + /* This branch may be executed with Pager.journalMode==MEMORY if + ** a hot-journal was just rolled back. In this case the journal + ** file should be closed and deleted. If this connection writes to + ** the database file, it will do so using an in-memory journal. + */ + int bDelete = !pPager->tempFile; + assert( sqlite3JournalIsInMemory(pPager->jfd)==0 ); + assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE + || pPager->journalMode==PAGER_JOURNALMODE_MEMORY + || pPager->journalMode==PAGER_JOURNALMODE_WAL + ); + sqlite3OsClose(pPager->jfd); + if( bDelete ){ + rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, pPager->extraSync); + } + } + } + +#ifdef SQLITE_CHECK_PAGES + sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash); + if( pPager->dbSize==0 && sqlite3PcacheRefCount(pPager->pPCache)>0 ){ + PgHdr *p = sqlite3PagerLookup(pPager, 1); + if( p ){ + p->pageHash = 0; + sqlite3PagerUnrefNotNull(p); + } + } +#endif + + sqlite3BitvecDestroy(pPager->pInJournal); + pPager->pInJournal = 0; + pPager->nRec = 0; + if( rc==SQLITE_OK ){ + if( MEMDB || pagerFlushOnCommit(pPager, bCommit) ){ + sqlite3PcacheCleanAll(pPager->pPCache); + }else{ + sqlite3PcacheClearWritable(pPager->pPCache); + } + sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize); + } + + if( pagerUseWal(pPager) ){ + /* Drop the WAL write-lock, if any. Also, if the connection was in + ** locking_mode=exclusive mode but is no longer, drop the EXCLUSIVE + ** lock held on the database file. + */ + rc2 = sqlite3WalEndWriteTransaction(pPager->pWal); + assert( rc2==SQLITE_OK ); + }else if( rc==SQLITE_OK && bCommit && pPager->dbFileSize>pPager->dbSize ){ + /* This branch is taken when committing a transaction in rollback-journal + ** mode if the database file on disk is larger than the database image. + ** At this point the journal has been finalized and the transaction + ** successfully committed, but the EXCLUSIVE lock is still held on the + ** file. So it is safe to truncate the database file to its minimum + ** required size. */ + assert( pPager->eLock==EXCLUSIVE_LOCK ); + rc = pager_truncate(pPager, pPager->dbSize); + } + + if( rc==SQLITE_OK && bCommit ){ + rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0); + if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK; + } + + if( !pPager->exclusiveMode + && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0)) + ){ + rc2 = pagerUnlockDb(pPager, SHARED_LOCK); + } + pPager->eState = PAGER_READER; + pPager->setSuper = 0; + + return (rc==SQLITE_OK?rc2:rc); +} + +/* Forward reference */ +static int pager_playback(Pager *pPager, int isHot); + +/* +** Execute a rollback if a transaction is active and unlock the +** database file. +** +** If the pager has already entered the ERROR state, do not attempt +** the rollback at this time. Instead, pager_unlock() is called. The +** call to pager_unlock() will discard all in-memory pages, unlock +** the database file and move the pager back to OPEN state. If this +** means that there is a hot-journal left in the file-system, the next +** connection to obtain a shared lock on the pager (which may be this one) +** will roll it back. +** +** If the pager has not already entered the ERROR state, but an IO or +** malloc error occurs during a rollback, then this will itself cause +** the pager to enter the ERROR state. Which will be cleared by the +** call to pager_unlock(), as described above. +*/ +static void pagerUnlockAndRollback(Pager *pPager){ + if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_OPEN ){ + assert( assert_pager_state(pPager) ); + if( pPager->eState>=PAGER_WRITER_LOCKED ){ + sqlite3BeginBenignMalloc(); + sqlite3PagerRollback(pPager); + sqlite3EndBenignMalloc(); + }else if( !pPager->exclusiveMode ){ + assert( pPager->eState==PAGER_READER ); + pager_end_transaction(pPager, 0, 0); + } + }else if( pPager->eState==PAGER_ERROR + && pPager->journalMode==PAGER_JOURNALMODE_MEMORY + && isOpen(pPager->jfd) + ){ + /* Special case for a ROLLBACK due to I/O error with an in-memory + ** journal: We have to rollback immediately, before the journal is + ** closed, because once it is closed, all content is forgotten. */ + int errCode = pPager->errCode; + u8 eLock = pPager->eLock; + pPager->eState = PAGER_OPEN; + pPager->errCode = SQLITE_OK; + pPager->eLock = EXCLUSIVE_LOCK; + pager_playback(pPager, 1); + pPager->errCode = errCode; + pPager->eLock = eLock; + } + pager_unlock(pPager); +} + +/* +** Parameter aData must point to a buffer of pPager->pageSize bytes +** of data. Compute and return a checksum based on the contents of the +** page of data and the current value of pPager->cksumInit. +** +** This is not a real checksum. It is really just the sum of the +** random initial value (pPager->cksumInit) and every 200th byte +** of the page data, starting with byte offset (pPager->pageSize%200). +** Each byte is interpreted as an 8-bit unsigned integer. +** +** Changing the formula used to compute this checksum results in an +** incompatible journal file format. +** +** If journal corruption occurs due to a power failure, the most likely +** scenario is that one end or the other of the record will be changed. +** It is much less likely that the two ends of the journal record will be +** correct and the middle be corrupt. Thus, this "checksum" scheme, +** though fast and simple, catches the mostly likely kind of corruption. +*/ +static u32 pager_cksum(Pager *pPager, const u8 *aData){ + u32 cksum = pPager->cksumInit; /* Checksum value to return */ + int i = pPager->pageSize-200; /* Loop counter */ + while( i>0 ){ + cksum += aData[i]; + i -= 200; + } + return cksum; +} + +/* +** Read a single page from either the journal file (if isMainJrnl==1) or +** from the sub-journal (if isMainJrnl==0) and playback that page. +** The page begins at offset *pOffset into the file. The *pOffset +** value is increased to the start of the next page in the journal. +** +** The main rollback journal uses checksums - the statement journal does +** not. +** +** If the page number of the page record read from the (sub-)journal file +** is greater than the current value of Pager.dbSize, then playback is +** skipped and SQLITE_OK is returned. +** +** If pDone is not NULL, then it is a record of pages that have already +** been played back. If the page at *pOffset has already been played back +** (if the corresponding pDone bit is set) then skip the playback. +** Make sure the pDone bit corresponding to the *pOffset page is set +** prior to returning. +** +** If the page record is successfully read from the (sub-)journal file +** and played back, then SQLITE_OK is returned. If an IO error occurs +** while reading the record from the (sub-)journal file or while writing +** to the database file, then the IO error code is returned. If data +** is successfully read from the (sub-)journal file but appears to be +** corrupted, SQLITE_DONE is returned. Data is considered corrupted in +** two circumstances: +** +** * If the record page-number is illegal (0 or PAGER_SJ_PGNO), or +** * If the record is being rolled back from the main journal file +** and the checksum field does not match the record content. +** +** Neither of these two scenarios are possible during a savepoint rollback. +** +** If this is a savepoint rollback, then memory may have to be dynamically +** allocated by this function. If this is the case and an allocation fails, +** SQLITE_NOMEM is returned. +*/ +static int pager_playback_one_page( + Pager *pPager, /* The pager being played back */ + i64 *pOffset, /* Offset of record to playback */ + Bitvec *pDone, /* Bitvec of pages already played back */ + int isMainJrnl, /* 1 -> main journal. 0 -> sub-journal. */ + int isSavepnt /* True for a savepoint rollback */ +){ + int rc; + PgHdr *pPg; /* An existing page in the cache */ + Pgno pgno; /* The page number of a page in journal */ + u32 cksum; /* Checksum used for sanity checking */ + char *aData; /* Temporary storage for the page */ + sqlite3_file *jfd; /* The file descriptor for the journal file */ + int isSynced; /* True if journal page is synced */ + + assert( (isMainJrnl&~1)==0 ); /* isMainJrnl is 0 or 1 */ + assert( (isSavepnt&~1)==0 ); /* isSavepnt is 0 or 1 */ + assert( isMainJrnl || pDone ); /* pDone always used on sub-journals */ + assert( isSavepnt || pDone==0 ); /* pDone never used on non-savepoint */ + + aData = pPager->pTmpSpace; + assert( aData ); /* Temp storage must have already been allocated */ + assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) ); + + /* Either the state is greater than PAGER_WRITER_CACHEMOD (a transaction + ** or savepoint rollback done at the request of the caller) or this is + ** a hot-journal rollback. If it is a hot-journal rollback, the pager + ** is in state OPEN and holds an EXCLUSIVE lock. Hot-journal rollback + ** only reads from the main journal, not the sub-journal. + */ + assert( pPager->eState>=PAGER_WRITER_CACHEMOD + || (pPager->eState==PAGER_OPEN && pPager->eLock==EXCLUSIVE_LOCK) + ); + assert( pPager->eState>=PAGER_WRITER_CACHEMOD || isMainJrnl ); + + /* Read the page number and page data from the journal or sub-journal + ** file. Return an error code to the caller if an IO error occurs. + */ + jfd = isMainJrnl ? pPager->jfd : pPager->sjfd; + rc = read32bits(jfd, *pOffset, &pgno); + if( rc!=SQLITE_OK ) return rc; + rc = sqlite3OsRead(jfd, (u8*)aData, pPager->pageSize, (*pOffset)+4); + if( rc!=SQLITE_OK ) return rc; + *pOffset += pPager->pageSize + 4 + isMainJrnl*4; + + /* Sanity checking on the page. This is more important that I originally + ** thought. If a power failure occurs while the journal is being written, + ** it could cause invalid data to be written into the journal. We need to + ** detect this invalid data (with high probability) and ignore it. + */ + if( pgno==0 || pgno==PAGER_SJ_PGNO(pPager) ){ + assert( !isSavepnt ); + return SQLITE_DONE; + } + if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){ + return SQLITE_OK; + } + if( isMainJrnl ){ + rc = read32bits(jfd, (*pOffset)-4, &cksum); + if( rc ) return rc; + if( !isSavepnt && pager_cksum(pPager, (u8*)aData)!=cksum ){ + return SQLITE_DONE; + } + } + + /* If this page has already been played back before during the current + ** rollback, then don't bother to play it back again. + */ + if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){ + return rc; + } + + /* When playing back page 1, restore the nReserve setting + */ + if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){ + pPager->nReserve = ((u8*)aData)[20]; + } + + /* If the pager is in CACHEMOD state, then there must be a copy of this + ** page in the pager cache. In this case just update the pager cache, + ** not the database file. The page is left marked dirty in this case. + ** + ** An exception to the above rule: If the database is in no-sync mode + ** and a page is moved during an incremental vacuum then the page may + ** not be in the pager cache. Later: if a malloc() or IO error occurs + ** during a Movepage() call, then the page may not be in the cache + ** either. So the condition described in the above paragraph is not + ** assert()able. + ** + ** If in WRITER_DBMOD, WRITER_FINISHED or OPEN state, then we update the + ** pager cache if it exists and the main file. The page is then marked + ** not dirty. Since this code is only executed in PAGER_OPEN state for + ** a hot-journal rollback, it is guaranteed that the page-cache is empty + ** if the pager is in OPEN state. + ** + ** Ticket #1171: The statement journal might contain page content that is + ** different from the page content at the start of the transaction. + ** This occurs when a page is changed prior to the start of a statement + ** then changed again within the statement. When rolling back such a + ** statement we must not write to the original database unless we know + ** for certain that original page contents are synced into the main rollback + ** journal. Otherwise, a power loss might leave modified data in the + ** database file without an entry in the rollback journal that can + ** restore the database to its original form. Two conditions must be + ** met before writing to the database files. (1) the database must be + ** locked. (2) we know that the original page content is fully synced + ** in the main journal either because the page is not in cache or else + ** the page is marked as needSync==0. + ** + ** 2008-04-14: When attempting to vacuum a corrupt database file, it + ** is possible to fail a statement on a database that does not yet exist. + ** Do not attempt to write if database file has never been opened. + */ + if( pagerUseWal(pPager) ){ + pPg = 0; + }else{ + pPg = sqlite3PagerLookup(pPager, pgno); + } + assert( pPg || !MEMDB ); + assert( pPager->eState!=PAGER_OPEN || pPg==0 || pPager->tempFile ); + PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n", + PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData), + (isMainJrnl?"main-journal":"sub-journal") + )); + if( isMainJrnl ){ + isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr); + }else{ + isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC)); + } + if( isOpen(pPager->fd) + && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) + && isSynced + ){ + i64 ofst = (pgno-1)*(i64)pPager->pageSize; + testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 ); + assert( !pagerUseWal(pPager) ); + + /* Write the data read from the journal back into the database file. + ** This is usually safe even for an encrypted database - as the data + ** was encrypted before it was written to the journal file. The exception + ** is if the data was just read from an in-memory sub-journal. In that + ** case it must be encrypted here before it is copied into the database + ** file. */ + rc = sqlite3OsWrite(pPager->fd, (u8 *)aData, pPager->pageSize, ofst); + + if( pgno>pPager->dbFileSize ){ + pPager->dbFileSize = pgno; + } + if( pPager->pBackup ){ + sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)aData); + } + }else if( !isMainJrnl && pPg==0 ){ + /* If this is a rollback of a savepoint and data was not written to + ** the database and the page is not in-memory, there is a potential + ** problem. When the page is next fetched by the b-tree layer, it + ** will be read from the database file, which may or may not be + ** current. + ** + ** There are a couple of different ways this can happen. All are quite + ** obscure. When running in synchronous mode, this can only happen + ** if the page is on the free-list at the start of the transaction, then + ** populated, then moved using sqlite3PagerMovepage(). + ** + ** The solution is to add an in-memory page to the cache containing + ** the data just read from the sub-journal. Mark the page as dirty + ** and if the pager requires a journal-sync, then mark the page as + ** requiring a journal-sync before it is written. + */ + assert( isSavepnt ); + assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)==0 ); + pPager->doNotSpill |= SPILLFLAG_ROLLBACK; + rc = sqlite3PagerGet(pPager, pgno, &pPg, 1); + assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)!=0 ); + pPager->doNotSpill &= ~SPILLFLAG_ROLLBACK; + if( rc!=SQLITE_OK ) return rc; + sqlite3PcacheMakeDirty(pPg); + } + if( pPg ){ + /* No page should ever be explicitly rolled back that is in use, except + ** for page 1 which is held in use in order to keep the lock on the + ** database active. However such a page may be rolled back as a result + ** of an internal error resulting in an automatic call to + ** sqlite3PagerRollback(). + */ + void *pData; + pData = pPg->pData; + memcpy(pData, (u8*)aData, pPager->pageSize); + pPager->xReiniter(pPg); + /* It used to be that sqlite3PcacheMakeClean(pPg) was called here. But + ** that call was dangerous and had no detectable benefit since the cache + ** is normally cleaned by sqlite3PcacheCleanAll() after rollback and so + ** has been removed. */ + pager_set_pagehash(pPg); + + /* If this was page 1, then restore the value of Pager.dbFileVers. + ** Do this before any decoding. */ + if( pgno==1 ){ + memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers)); + } + sqlite3PcacheRelease(pPg); + } + return rc; +} + +/* +** Parameter zSuper is the name of a super-journal file. A single journal +** file that referred to the super-journal file has just been rolled back. +** This routine checks if it is possible to delete the super-journal file, +** and does so if it is. +** +** Argument zSuper may point to Pager.pTmpSpace. So that buffer is not +** available for use within this function. +** +** When a super-journal file is created, it is populated with the names +** of all of its child journals, one after another, formatted as utf-8 +** encoded text. The end of each child journal file is marked with a +** nul-terminator byte (0x00). i.e. the entire contents of a super-journal +** file for a transaction involving two databases might be: +** +** "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00" +** +** A super-journal file may only be deleted once all of its child +** journals have been rolled back. +** +** This function reads the contents of the super-journal file into +** memory and loops through each of the child journal names. For +** each child journal, it checks if: +** +** * if the child journal exists, and if so +** * if the child journal contains a reference to super-journal +** file zSuper +** +** If a child journal can be found that matches both of the criteria +** above, this function returns without doing anything. Otherwise, if +** no such child journal can be found, file zSuper is deleted from +** the file-system using sqlite3OsDelete(). +** +** If an IO error within this function, an error code is returned. This +** function allocates memory by calling sqlite3Malloc(). If an allocation +** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors +** occur, SQLITE_OK is returned. +** +** TODO: This function allocates a single block of memory to load +** the entire contents of the super-journal file. This could be +** a couple of kilobytes or so - potentially larger than the page +** size. +*/ +static int pager_delsuper(Pager *pPager, const char *zSuper){ + sqlite3_vfs *pVfs = pPager->pVfs; + int rc; /* Return code */ + sqlite3_file *pSuper; /* Malloc'd super-journal file descriptor */ + sqlite3_file *pJournal; /* Malloc'd child-journal file descriptor */ + char *zSuperJournal = 0; /* Contents of super-journal file */ + i64 nSuperJournal; /* Size of super-journal file */ + char *zJournal; /* Pointer to one journal within MJ file */ + char *zSuperPtr; /* Space to hold super-journal filename */ + char *zFree = 0; /* Free this buffer */ + int nSuperPtr; /* Amount of space allocated to zSuperPtr[] */ + + /* Allocate space for both the pJournal and pSuper file descriptors. + ** If successful, open the super-journal file for reading. + */ + pSuper = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2); + if( !pSuper ){ + rc = SQLITE_NOMEM_BKPT; + pJournal = 0; + }else{ + const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_SUPER_JOURNAL); + rc = sqlite3OsOpen(pVfs, zSuper, pSuper, flags, 0); + pJournal = (sqlite3_file *)(((u8 *)pSuper) + pVfs->szOsFile); + } + if( rc!=SQLITE_OK ) goto delsuper_out; + + /* Load the entire super-journal file into space obtained from + ** sqlite3_malloc() and pointed to by zSuperJournal. Also obtain + ** sufficient space (in zSuperPtr) to hold the names of super-journal + ** files extracted from regular rollback-journals. + */ + rc = sqlite3OsFileSize(pSuper, &nSuperJournal); + if( rc!=SQLITE_OK ) goto delsuper_out; + nSuperPtr = pVfs->mxPathname+1; + zFree = sqlite3Malloc(4 + nSuperJournal + nSuperPtr + 2); + if( !zFree ){ + rc = SQLITE_NOMEM_BKPT; + goto delsuper_out; + } + zFree[0] = zFree[1] = zFree[2] = zFree[3] = 0; + zSuperJournal = &zFree[4]; + zSuperPtr = &zSuperJournal[nSuperJournal+2]; + rc = sqlite3OsRead(pSuper, zSuperJournal, (int)nSuperJournal, 0); + if( rc!=SQLITE_OK ) goto delsuper_out; + zSuperJournal[nSuperJournal] = 0; + zSuperJournal[nSuperJournal+1] = 0; + + zJournal = zSuperJournal; + while( (zJournal-zSuperJournal)<nSuperJournal ){ + int exists; + rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists); + if( rc!=SQLITE_OK ){ + goto delsuper_out; + } + if( exists ){ + /* One of the journals pointed to by the super-journal exists. + ** Open it and check if it points at the super-journal. If + ** so, return without deleting the super-journal file. + ** NB: zJournal is really a MAIN_JOURNAL. But call it a + ** SUPER_JOURNAL here so that the VFS will not send the zJournal + ** name into sqlite3_database_file_object(). + */ + int c; + int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_SUPER_JOURNAL); + rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0); + if( rc!=SQLITE_OK ){ + goto delsuper_out; + } + + rc = readSuperJournal(pJournal, zSuperPtr, nSuperPtr); + sqlite3OsClose(pJournal); + if( rc!=SQLITE_OK ){ + goto delsuper_out; + } + + c = zSuperPtr[0]!=0 && strcmp(zSuperPtr, zSuper)==0; + if( c ){ + /* We have a match. Do not delete the super-journal file. */ + goto delsuper_out; + } + } + zJournal += (sqlite3Strlen30(zJournal)+1); + } + + sqlite3OsClose(pSuper); + rc = sqlite3OsDelete(pVfs, zSuper, 0); + +delsuper_out: + sqlite3_free(zFree); + if( pSuper ){ + sqlite3OsClose(pSuper); + assert( !isOpen(pJournal) ); + sqlite3_free(pSuper); + } + return rc; +} + + +/* +** This function is used to change the actual size of the database +** file in the file-system. This only happens when committing a transaction, +** or rolling back a transaction (including rolling back a hot-journal). +** +** If the main database file is not open, or the pager is not in either +** DBMOD or OPEN state, this function is a no-op. Otherwise, the size +** of the file is changed to nPage pages (nPage*pPager->pageSize bytes). +** If the file on disk is currently larger than nPage pages, then use the VFS +** xTruncate() method to truncate it. +** +** Or, it might be the case that the file on disk is smaller than +** nPage pages. Some operating system implementations can get confused if +** you try to truncate a file to some size that is larger than it +** currently is, so detect this case and write a single zero byte to +** the end of the new file instead. +** +** If successful, return SQLITE_OK. If an IO error occurs while modifying +** the database file, return the error code to the caller. +*/ +static int pager_truncate(Pager *pPager, Pgno nPage){ + int rc = SQLITE_OK; + assert( pPager->eState!=PAGER_ERROR ); + assert( pPager->eState!=PAGER_READER ); + PAGERTRACE(("Truncate %d npage %u\n", PAGERID(pPager), nPage)); + + + if( isOpen(pPager->fd) + && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) + ){ + i64 currentSize, newSize; + int szPage = pPager->pageSize; + assert( pPager->eLock==EXCLUSIVE_LOCK ); + /* TODO: Is it safe to use Pager.dbFileSize here? */ + rc = sqlite3OsFileSize(pPager->fd, ¤tSize); + newSize = szPage*(i64)nPage; + if( rc==SQLITE_OK && currentSize!=newSize ){ + if( currentSize>newSize ){ + rc = sqlite3OsTruncate(pPager->fd, newSize); + }else if( (currentSize+szPage)<=newSize ){ + char *pTmp = pPager->pTmpSpace; + memset(pTmp, 0, szPage); + testcase( (newSize-szPage) == currentSize ); + testcase( (newSize-szPage) > currentSize ); + sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &newSize); + rc = sqlite3OsWrite(pPager->fd, pTmp, szPage, newSize-szPage); + } + if( rc==SQLITE_OK ){ + pPager->dbFileSize = nPage; + } + } + } + return rc; +} + +/* +** Return a sanitized version of the sector-size of OS file pFile. The +** return value is guaranteed to lie between 32 and MAX_SECTOR_SIZE. +*/ +int sqlite3SectorSize(sqlite3_file *pFile){ + int iRet = sqlite3OsSectorSize(pFile); + if( iRet<32 ){ + iRet = 512; + }else if( iRet>MAX_SECTOR_SIZE ){ + assert( MAX_SECTOR_SIZE>=512 ); + iRet = MAX_SECTOR_SIZE; + } + return iRet; +} + +/* +** Set the value of the Pager.sectorSize variable for the given +** pager based on the value returned by the xSectorSize method +** of the open database file. The sector size will be used +** to determine the size and alignment of journal header and +** super-journal pointers within created journal files. +** +** For temporary files the effective sector size is always 512 bytes. +** +** Otherwise, for non-temporary files, the effective sector size is +** the value returned by the xSectorSize() method rounded up to 32 if +** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it +** is greater than MAX_SECTOR_SIZE. +** +** If the file has the SQLITE_IOCAP_POWERSAFE_OVERWRITE property, then set +** the effective sector size to its minimum value (512). The purpose of +** pPager->sectorSize is to define the "blast radius" of bytes that +** might change if a crash occurs while writing to a single byte in +** that range. But with POWERSAFE_OVERWRITE, the blast radius is zero +** (that is what POWERSAFE_OVERWRITE means), so we minimize the sector +** size. For backwards compatibility of the rollback journal file format, +** we cannot reduce the effective sector size below 512. +*/ +static void setSectorSize(Pager *pPager){ + assert( isOpen(pPager->fd) || pPager->tempFile ); + + if( pPager->tempFile + || (sqlite3OsDeviceCharacteristics(pPager->fd) & + SQLITE_IOCAP_POWERSAFE_OVERWRITE)!=0 + ){ + /* Sector size doesn't matter for temporary files. Also, the file + ** may not have been opened yet, in which case the OsSectorSize() + ** call will segfault. */ + pPager->sectorSize = 512; + }else{ + pPager->sectorSize = sqlite3SectorSize(pPager->fd); + } +} + +/* +** Playback the journal and thus restore the database file to +** the state it was in before we started making changes. +** +** The journal file format is as follows: +** +** (1) 8 byte prefix. A copy of aJournalMagic[]. +** (2) 4 byte big-endian integer which is the number of valid page records +** in the journal. If this value is 0xffffffff, then compute the +** number of page records from the journal size. +** (3) 4 byte big-endian integer which is the initial value for the +** sanity checksum. +** (4) 4 byte integer which is the number of pages to truncate the +** database to during a rollback. +** (5) 4 byte big-endian integer which is the sector size. The header +** is this many bytes in size. +** (6) 4 byte big-endian integer which is the page size. +** (7) zero padding out to the next sector size. +** (8) Zero or more pages instances, each as follows: +** + 4 byte page number. +** + pPager->pageSize bytes of data. +** + 4 byte checksum +** +** When we speak of the journal header, we mean the first 7 items above. +** Each entry in the journal is an instance of the 8th item. +** +** Call the value from the second bullet "nRec". nRec is the number of +** valid page entries in the journal. In most cases, you can compute the +** value of nRec from the size of the journal file. But if a power +** failure occurred while the journal was being written, it could be the +** case that the size of the journal file had already been increased but +** the extra entries had not yet made it safely to disk. In such a case, +** the value of nRec computed from the file size would be too large. For +** that reason, we always use the nRec value in the header. +** +** If the nRec value is 0xffffffff it means that nRec should be computed +** from the file size. This value is used when the user selects the +** no-sync option for the journal. A power failure could lead to corruption +** in this case. But for things like temporary table (which will be +** deleted when the power is restored) we don't care. +** +** If the file opened as the journal file is not a well-formed +** journal file then all pages up to the first corrupted page are rolled +** back (or no pages if the journal header is corrupted). The journal file +** is then deleted and SQLITE_OK returned, just as if no corruption had +** been encountered. +** +** If an I/O or malloc() error occurs, the journal-file is not deleted +** and an error code is returned. +** +** The isHot parameter indicates that we are trying to rollback a journal +** that might be a hot journal. Or, it could be that the journal is +** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE. +** If the journal really is hot, reset the pager cache prior rolling +** back any content. If the journal is merely persistent, no reset is +** needed. +*/ +static int pager_playback(Pager *pPager, int isHot){ + sqlite3_vfs *pVfs = pPager->pVfs; + i64 szJ; /* Size of the journal file in bytes */ + u32 nRec; /* Number of Records in the journal */ + u32 u; /* Unsigned loop counter */ + Pgno mxPg = 0; /* Size of the original file in pages */ + int rc; /* Result code of a subroutine */ + int res = 1; /* Value returned by sqlite3OsAccess() */ + char *zSuper = 0; /* Name of super-journal file if any */ + int needPagerReset; /* True to reset page prior to first page rollback */ + int nPlayback = 0; /* Total number of pages restored from journal */ + u32 savedPageSize = pPager->pageSize; + + /* Figure out how many records are in the journal. Abort early if + ** the journal is empty. + */ + assert( isOpen(pPager->jfd) ); + rc = sqlite3OsFileSize(pPager->jfd, &szJ); + if( rc!=SQLITE_OK ){ + goto end_playback; + } + + /* Read the super-journal name from the journal, if it is present. + ** If a super-journal file name is specified, but the file is not + ** present on disk, then the journal is not hot and does not need to be + ** played back. + ** + ** TODO: Technically the following is an error because it assumes that + ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that + ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c, + ** mxPathname is 512, which is the same as the minimum allowable value + ** for pageSize. + */ + zSuper = pPager->pTmpSpace; + rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1); + if( rc==SQLITE_OK && zSuper[0] ){ + rc = sqlite3OsAccess(pVfs, zSuper, SQLITE_ACCESS_EXISTS, &res); + } + zSuper = 0; + if( rc!=SQLITE_OK || !res ){ + goto end_playback; + } + pPager->journalOff = 0; + needPagerReset = isHot; + + /* This loop terminates either when a readJournalHdr() or + ** pager_playback_one_page() call returns SQLITE_DONE or an IO error + ** occurs. + */ + while( 1 ){ + /* Read the next journal header from the journal file. If there are + ** not enough bytes left in the journal file for a complete header, or + ** it is corrupted, then a process must have failed while writing it. + ** This indicates nothing more needs to be rolled back. + */ + rc = readJournalHdr(pPager, isHot, szJ, &nRec, &mxPg); + if( rc!=SQLITE_OK ){ + if( rc==SQLITE_DONE ){ + rc = SQLITE_OK; + } + goto end_playback; + } + + /* If nRec is 0xffffffff, then this journal was created by a process + ** working in no-sync mode. This means that the rest of the journal + ** file consists of pages, there are no more journal headers. Compute + ** the value of nRec based on this assumption. + */ + if( nRec==0xffffffff ){ + assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ); + nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager)); + } + + /* If nRec is 0 and this rollback is of a transaction created by this + ** process and if this is the final header in the journal, then it means + ** that this part of the journal was being filled but has not yet been + ** synced to disk. Compute the number of pages based on the remaining + ** size of the file. + ** + ** The third term of the test was added to fix ticket #2565. + ** When rolling back a hot journal, nRec==0 always means that the next + ** chunk of the journal contains zero pages to be rolled back. But + ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in + ** the journal, it means that the journal might contain additional + ** pages that need to be rolled back and that the number of pages + ** should be computed based on the journal file size. + */ + if( nRec==0 && !isHot && + pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){ + nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager)); + } + + /* If this is the first header read from the journal, truncate the + ** database file back to its original size. + */ + if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){ + rc = pager_truncate(pPager, mxPg); + if( rc!=SQLITE_OK ){ + goto end_playback; + } + pPager->dbSize = mxPg; + if( pPager->mxPgno<mxPg ){ + pPager->mxPgno = mxPg; + } + } + + /* Copy original pages out of the journal and back into the + ** database file and/or page cache. + */ + for(u=0; u<nRec; u++){ + if( needPagerReset ){ + pager_reset(pPager); + needPagerReset = 0; + } + rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0); + if( rc==SQLITE_OK ){ + nPlayback++; + }else{ + if( rc==SQLITE_DONE ){ + pPager->journalOff = szJ; + break; + }else if( rc==SQLITE_IOERR_SHORT_READ ){ + /* If the journal has been truncated, simply stop reading and + ** processing the journal. This might happen if the journal was + ** not completely written and synced prior to a crash. In that + ** case, the database should have never been written in the + ** first place so it is OK to simply abandon the rollback. */ + rc = SQLITE_OK; + goto end_playback; + }else{ + /* If we are unable to rollback, quit and return the error + ** code. This will cause the pager to enter the error state + ** so that no further harm will be done. Perhaps the next + ** process to come along will be able to rollback the database. + */ + goto end_playback; + } + } + } + } + /*NOTREACHED*/ + assert( 0 ); + +end_playback: + if( rc==SQLITE_OK ){ + rc = sqlite3PagerSetPagesize(pPager, &savedPageSize, -1); + } + /* Following a rollback, the database file should be back in its original + ** state prior to the start of the transaction, so invoke the + ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the + ** assertion that the transaction counter was modified. + */ +#ifdef SQLITE_DEBUG + sqlite3OsFileControlHint(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0); +#endif + + /* If this playback is happening automatically as a result of an IO or + ** malloc error that occurred after the change-counter was updated but + ** before the transaction was committed, then the change-counter + ** modification may just have been reverted. If this happens in exclusive + ** mode, then subsequent transactions performed by the connection will not + ** update the change-counter at all. This may lead to cache inconsistency + ** problems for other processes at some point in the future. So, just + ** in case this has happened, clear the changeCountDone flag now. + */ + pPager->changeCountDone = pPager->tempFile; + + if( rc==SQLITE_OK ){ + /* Leave 4 bytes of space before the super-journal filename in memory. + ** This is because it may end up being passed to sqlite3OsOpen(), in + ** which case it requires 4 0x00 bytes in memory immediately before + ** the filename. */ + zSuper = &pPager->pTmpSpace[4]; + rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1); + testcase( rc!=SQLITE_OK ); + } + if( rc==SQLITE_OK + && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) + ){ + rc = sqlite3PagerSync(pPager, 0); + } + if( rc==SQLITE_OK ){ + rc = pager_end_transaction(pPager, zSuper[0]!='\0', 0); + testcase( rc!=SQLITE_OK ); + } + if( rc==SQLITE_OK && zSuper[0] && res ){ + /* If there was a super-journal and this routine will return success, + ** see if it is possible to delete the super-journal. + */ + assert( zSuper==&pPager->pTmpSpace[4] ); + memset(pPager->pTmpSpace, 0, 4); + rc = pager_delsuper(pPager, zSuper); + testcase( rc!=SQLITE_OK ); + } + if( isHot && nPlayback ){ + sqlite3_log(SQLITE_NOTICE_RECOVER_ROLLBACK, "recovered %d pages from %s", + nPlayback, pPager->zJournal); + } + + /* The Pager.sectorSize variable may have been updated while rolling + ** back a journal created by a process with a different sector size + ** value. Reset it to the correct value for this process. + */ + setSectorSize(pPager); + return rc; +} + + +/* +** Read the content for page pPg out of the database file (or out of +** the WAL if that is where the most recent copy if found) into +** pPg->pData. A shared lock or greater must be held on the database +** file before this function is called. +** +** If page 1 is read, then the value of Pager.dbFileVers[] is set to +** the value read from the database file. +** +** If an IO error occurs, then the IO error is returned to the caller. +** Otherwise, SQLITE_OK is returned. +*/ +static int readDbPage(PgHdr *pPg){ + Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */ + int rc = SQLITE_OK; /* Return code */ + +#ifndef SQLITE_OMIT_WAL + u32 iFrame = 0; /* Frame of WAL containing pgno */ + + assert( pPager->eState>=PAGER_READER && !MEMDB ); + assert( isOpen(pPager->fd) ); + + if( pagerUseWal(pPager) ){ + rc = sqlite3WalFindFrame(pPager->pWal, pPg->pgno, &iFrame); + if( rc ) return rc; + } + if( iFrame ){ + rc = sqlite3WalReadFrame(pPager->pWal, iFrame,pPager->pageSize,pPg->pData); + }else +#endif + { + i64 iOffset = (pPg->pgno-1)*(i64)pPager->pageSize; + rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset); + if( rc==SQLITE_IOERR_SHORT_READ ){ + rc = SQLITE_OK; + } + } + + if( pPg->pgno==1 ){ + if( rc ){ + /* If the read is unsuccessful, set the dbFileVers[] to something + ** that will never be a valid file version. dbFileVers[] is a copy + ** of bytes 24..39 of the database. Bytes 28..31 should always be + ** zero or the size of the database in page. Bytes 32..35 and 35..39 + ** should be page numbers which are never 0xffffffff. So filling + ** pPager->dbFileVers[] with all 0xff bytes should suffice. + ** + ** For an encrypted database, the situation is more complex: bytes + ** 24..39 of the database are white noise. But the probability of + ** white noise equaling 16 bytes of 0xff is vanishingly small so + ** we should still be ok. + */ + memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers)); + }else{ + u8 *dbFileVers = &((u8*)pPg->pData)[24]; + memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers)); + } + } + PAGER_INCR(sqlite3_pager_readdb_count); + PAGER_INCR(pPager->nRead); + IOTRACE(("PGIN %p %d\n", pPager, pPg->pgno)); + PAGERTRACE(("FETCH %d page %d hash(%08x)\n", + PAGERID(pPager), pPg->pgno, pager_pagehash(pPg))); + + return rc; +} + +/* +** Update the value of the change-counter at offsets 24 and 92 in +** the header and the sqlite version number at offset 96. +** +** This is an unconditional update. See also the pager_incr_changecounter() +** routine which only updates the change-counter if the update is actually +** needed, as determined by the pPager->changeCountDone state variable. +*/ +static void pager_write_changecounter(PgHdr *pPg){ + u32 change_counter; + if( NEVER(pPg==0) ) return; + + /* Increment the value just read and write it back to byte 24. */ + change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1; + put32bits(((char*)pPg->pData)+24, change_counter); + + /* Also store the SQLite version number in bytes 96..99 and in + ** bytes 92..95 store the change counter for which the version number + ** is valid. */ + put32bits(((char*)pPg->pData)+92, change_counter); + put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER); +} + +#ifndef SQLITE_OMIT_WAL +/* +** This function is invoked once for each page that has already been +** written into the log file when a WAL transaction is rolled back. +** Parameter iPg is the page number of said page. The pCtx argument +** is actually a pointer to the Pager structure. +** +** If page iPg is present in the cache, and has no outstanding references, +** it is discarded. Otherwise, if there are one or more outstanding +** references, the page content is reloaded from the database. If the +** attempt to reload content from the database is required and fails, +** return an SQLite error code. Otherwise, SQLITE_OK. +*/ +static int pagerUndoCallback(void *pCtx, Pgno iPg){ + int rc = SQLITE_OK; + Pager *pPager = (Pager *)pCtx; + PgHdr *pPg; + + assert( pagerUseWal(pPager) ); + pPg = sqlite3PagerLookup(pPager, iPg); + if( pPg ){ + if( sqlite3PcachePageRefcount(pPg)==1 ){ + sqlite3PcacheDrop(pPg); + }else{ + rc = readDbPage(pPg); + if( rc==SQLITE_OK ){ + pPager->xReiniter(pPg); + } + sqlite3PagerUnrefNotNull(pPg); + } + } + + /* Normally, if a transaction is rolled back, any backup processes are + ** updated as data is copied out of the rollback journal and into the + ** database. This is not generally possible with a WAL database, as + ** rollback involves simply truncating the log file. Therefore, if one + ** or more frames have already been written to the log (and therefore + ** also copied into the backup databases) as part of this transaction, + ** the backups must be restarted. + */ + sqlite3BackupRestart(pPager->pBackup); + + return rc; +} + +/* +** This function is called to rollback a transaction on a WAL database. +*/ +static int pagerRollbackWal(Pager *pPager){ + int rc; /* Return Code */ + PgHdr *pList; /* List of dirty pages to revert */ + + /* For all pages in the cache that are currently dirty or have already + ** been written (but not committed) to the log file, do one of the + ** following: + ** + ** + Discard the cached page (if refcount==0), or + ** + Reload page content from the database (if refcount>0). + */ + pPager->dbSize = pPager->dbOrigSize; + rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager); + pList = sqlite3PcacheDirtyList(pPager->pPCache); + while( pList && rc==SQLITE_OK ){ + PgHdr *pNext = pList->pDirty; + rc = pagerUndoCallback((void *)pPager, pList->pgno); + pList = pNext; + } + + return rc; +} + +/* +** This function is a wrapper around sqlite3WalFrames(). As well as logging +** the contents of the list of pages headed by pList (connected by pDirty), +** this function notifies any active backup processes that the pages have +** changed. +** +** The list of pages passed into this routine is always sorted by page number. +** Hence, if page 1 appears anywhere on the list, it will be the first page. +*/ +static int pagerWalFrames( + Pager *pPager, /* Pager object */ + PgHdr *pList, /* List of frames to log */ + Pgno nTruncate, /* Database size after this commit */ + int isCommit /* True if this is a commit */ +){ + int rc; /* Return code */ + int nList; /* Number of pages in pList */ + PgHdr *p; /* For looping over pages */ + + assert( pPager->pWal ); + assert( pList ); +#ifdef SQLITE_DEBUG + /* Verify that the page list is in ascending order */ + for(p=pList; p && p->pDirty; p=p->pDirty){ + assert( p->pgno < p->pDirty->pgno ); + } +#endif + + assert( pList->pDirty==0 || isCommit ); + if( isCommit ){ + /* If a WAL transaction is being committed, there is no point in writing + ** any pages with page numbers greater than nTruncate into the WAL file. + ** They will never be read by any client. So remove them from the pDirty + ** list here. */ + PgHdr **ppNext = &pList; + nList = 0; + for(p=pList; (*ppNext = p)!=0; p=p->pDirty){ + if( p->pgno<=nTruncate ){ + ppNext = &p->pDirty; + nList++; + } + } + assert( pList ); + }else{ + nList = 1; + } + pPager->aStat[PAGER_STAT_WRITE] += nList; + + if( pList->pgno==1 ) pager_write_changecounter(pList); + rc = sqlite3WalFrames(pPager->pWal, + pPager->pageSize, pList, nTruncate, isCommit, pPager->walSyncFlags + ); + if( rc==SQLITE_OK && pPager->pBackup ){ + for(p=pList; p; p=p->pDirty){ + sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData); + } + } + +#ifdef SQLITE_CHECK_PAGES + pList = sqlite3PcacheDirtyList(pPager->pPCache); + for(p=pList; p; p=p->pDirty){ + pager_set_pagehash(p); + } +#endif + + return rc; +} + +/* +** Begin a read transaction on the WAL. +** +** This routine used to be called "pagerOpenSnapshot()" because it essentially +** makes a snapshot of the database at the current point in time and preserves +** that snapshot for use by the reader in spite of concurrently changes by +** other writers or checkpointers. +*/ +static int pagerBeginReadTransaction(Pager *pPager){ + int rc; /* Return code */ + int changed = 0; /* True if cache must be reset */ + + assert( pagerUseWal(pPager) ); + assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER ); + + /* sqlite3WalEndReadTransaction() was not called for the previous + ** transaction in locking_mode=EXCLUSIVE. So call it now. If we + ** are in locking_mode=NORMAL and EndRead() was previously called, + ** the duplicate call is harmless. + */ + sqlite3WalEndReadTransaction(pPager->pWal); + + rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed); + if( rc!=SQLITE_OK || changed ){ + pager_reset(pPager); + if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0); + } + + return rc; +} +#endif + +/* +** This function is called as part of the transition from PAGER_OPEN +** to PAGER_READER state to determine the size of the database file +** in pages (assuming the page size currently stored in Pager.pageSize). +** +** If no error occurs, SQLITE_OK is returned and the size of the database +** in pages is stored in *pnPage. Otherwise, an error code (perhaps +** SQLITE_IOERR_FSTAT) is returned and *pnPage is left unmodified. +*/ +static int pagerPagecount(Pager *pPager, Pgno *pnPage){ + Pgno nPage; /* Value to return via *pnPage */ + + /* Query the WAL sub-system for the database size. The WalDbsize() + ** function returns zero if the WAL is not open (i.e. Pager.pWal==0), or + ** if the database size is not available. The database size is not + ** available from the WAL sub-system if the log file is empty or + ** contains no valid committed transactions. + */ + assert( pPager->eState==PAGER_OPEN ); + assert( pPager->eLock>=SHARED_LOCK ); + assert( isOpen(pPager->fd) ); + assert( pPager->tempFile==0 ); + nPage = sqlite3WalDbsize(pPager->pWal); + + /* If the number of pages in the database is not available from the + ** WAL sub-system, determine the page count based on the size of + ** the database file. If the size of the database file is not an + ** integer multiple of the page-size, round up the result. + */ + if( nPage==0 && ALWAYS(isOpen(pPager->fd)) ){ + i64 n = 0; /* Size of db file in bytes */ + int rc = sqlite3OsFileSize(pPager->fd, &n); + if( rc!=SQLITE_OK ){ + return rc; + } + nPage = (Pgno)((n+pPager->pageSize-1) / pPager->pageSize); + } + + /* If the current number of pages in the file is greater than the + ** configured maximum pager number, increase the allowed limit so + ** that the file can be read. + */ + if( nPage>pPager->mxPgno ){ + pPager->mxPgno = (Pgno)nPage; + } + + *pnPage = nPage; + return SQLITE_OK; +} + +#ifndef SQLITE_OMIT_WAL +/* +** Check if the *-wal file that corresponds to the database opened by pPager +** exists if the database is not empty, or verify that the *-wal file does +** not exist (by deleting it) if the database file is empty. +** +** If the database is not empty and the *-wal file exists, open the pager +** in WAL mode. If the database is empty or if no *-wal file exists and +** if no error occurs, make sure Pager.journalMode is not set to +** PAGER_JOURNALMODE_WAL. +** +** Return SQLITE_OK or an error code. +** +** The caller must hold a SHARED lock on the database file to call this +** function. Because an EXCLUSIVE lock on the db file is required to delete +** a WAL on a none-empty database, this ensures there is no race condition +** between the xAccess() below and an xDelete() being executed by some +** other connection. +*/ +static int pagerOpenWalIfPresent(Pager *pPager){ + int rc = SQLITE_OK; + assert( pPager->eState==PAGER_OPEN ); + assert( pPager->eLock>=SHARED_LOCK ); + + if( !pPager->tempFile ){ + int isWal; /* True if WAL file exists */ + rc = sqlite3OsAccess( + pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &isWal + ); + if( rc==SQLITE_OK ){ + if( isWal ){ + Pgno nPage; /* Size of the database file */ + + rc = pagerPagecount(pPager, &nPage); + if( rc ) return rc; + if( nPage==0 ){ + rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0); + }else{ + testcase( sqlite3PcachePagecount(pPager->pPCache)==0 ); + rc = sqlite3PagerOpenWal(pPager, 0); + } + }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){ + pPager->journalMode = PAGER_JOURNALMODE_DELETE; + } + } + } + return rc; +} +#endif + +/* +** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback +** the entire super-journal file. The case pSavepoint==NULL occurs when +** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction +** savepoint. +** +** When pSavepoint is not NULL (meaning a non-transaction savepoint is +** being rolled back), then the rollback consists of up to three stages, +** performed in the order specified: +** +** * Pages are played back from the main journal starting at byte +** offset PagerSavepoint.iOffset and continuing to +** PagerSavepoint.iHdrOffset, or to the end of the main journal +** file if PagerSavepoint.iHdrOffset is zero. +** +** * If PagerSavepoint.iHdrOffset is not zero, then pages are played +** back starting from the journal header immediately following +** PagerSavepoint.iHdrOffset to the end of the main journal file. +** +** * Pages are then played back from the sub-journal file, starting +** with the PagerSavepoint.iSubRec and continuing to the end of +** the journal file. +** +** Throughout the rollback process, each time a page is rolled back, the +** corresponding bit is set in a bitvec structure (variable pDone in the +** implementation below). This is used to ensure that a page is only +** rolled back the first time it is encountered in either journal. +** +** If pSavepoint is NULL, then pages are only played back from the main +** journal file. There is no need for a bitvec in this case. +** +** In either case, before playback commences the Pager.dbSize variable +** is reset to the value that it held at the start of the savepoint +** (or transaction). No page with a page-number greater than this value +** is played back. If one is encountered it is simply skipped. +*/ +static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){ + i64 szJ; /* Effective size of the main journal */ + i64 iHdrOff; /* End of first segment of main-journal records */ + int rc = SQLITE_OK; /* Return code */ + Bitvec *pDone = 0; /* Bitvec to ensure pages played back only once */ + + assert( pPager->eState!=PAGER_ERROR ); + assert( pPager->eState>=PAGER_WRITER_LOCKED ); + + /* Allocate a bitvec to use to store the set of pages rolled back */ + if( pSavepoint ){ + pDone = sqlite3BitvecCreate(pSavepoint->nOrig); + if( !pDone ){ + return SQLITE_NOMEM_BKPT; + } + } + + /* Set the database size back to the value it was before the savepoint + ** being reverted was opened. + */ + pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize; + pPager->changeCountDone = pPager->tempFile; + + if( !pSavepoint && pagerUseWal(pPager) ){ + return pagerRollbackWal(pPager); + } + + /* Use pPager->journalOff as the effective size of the main rollback + ** journal. The actual file might be larger than this in + ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST. But anything + ** past pPager->journalOff is off-limits to us. + */ + szJ = pPager->journalOff; + assert( pagerUseWal(pPager)==0 || szJ==0 ); + + /* Begin by rolling back records from the main journal starting at + ** PagerSavepoint.iOffset and continuing to the next journal header. + ** There might be records in the main journal that have a page number + ** greater than the current database size (pPager->dbSize) but those + ** will be skipped automatically. Pages are added to pDone as they + ** are played back. + */ + if( pSavepoint && !pagerUseWal(pPager) ){ + iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ; + pPager->journalOff = pSavepoint->iOffset; + while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){ + rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1); + } + assert( rc!=SQLITE_DONE ); + }else{ + pPager->journalOff = 0; + } + + /* Continue rolling back records out of the main journal starting at + ** the first journal header seen and continuing until the effective end + ** of the main journal file. Continue to skip out-of-range pages and + ** continue adding pages rolled back to pDone. + */ + while( rc==SQLITE_OK && pPager->journalOff<szJ ){ + u32 ii; /* Loop counter */ + u32 nJRec = 0; /* Number of Journal Records */ + u32 dummy; + rc = readJournalHdr(pPager, 0, szJ, &nJRec, &dummy); + assert( rc!=SQLITE_DONE ); + + /* + ** The "pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff" + ** test is related to ticket #2565. See the discussion in the + ** pager_playback() function for additional information. + */ + if( nJRec==0 + && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff + ){ + nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager)); + } + for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){ + rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1); + } + assert( rc!=SQLITE_DONE ); + } + assert( rc!=SQLITE_OK || pPager->journalOff>=szJ ); + + /* Finally, rollback pages from the sub-journal. Page that were + ** previously rolled back out of the main journal (and are hence in pDone) + ** will be skipped. Out-of-range pages are also skipped. + */ + if( pSavepoint ){ + u32 ii; /* Loop counter */ + i64 offset = (i64)pSavepoint->iSubRec*(4+pPager->pageSize); + + if( pagerUseWal(pPager) ){ + rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData); + } + for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){ + assert( offset==(i64)ii*(4+pPager->pageSize) ); + rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1); + } + assert( rc!=SQLITE_DONE ); + } + + sqlite3BitvecDestroy(pDone); + if( rc==SQLITE_OK ){ + pPager->journalOff = szJ; + } + + return rc; +} + +/* +** Change the maximum number of in-memory pages that are allowed +** before attempting to recycle clean and unused pages. +*/ +void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){ + sqlite3PcacheSetCachesize(pPager->pPCache, mxPage); +} + +/* +** Change the maximum number of in-memory pages that are allowed +** before attempting to spill pages to journal. +*/ +int sqlite3PagerSetSpillsize(Pager *pPager, int mxPage){ + return sqlite3PcacheSetSpillsize(pPager->pPCache, mxPage); +} + +/* +** Invoke SQLITE_FCNTL_MMAP_SIZE based on the current value of szMmap. +*/ +static void pagerFixMaplimit(Pager *pPager){ +#if SQLITE_MAX_MMAP_SIZE>0 + sqlite3_file *fd = pPager->fd; + if( isOpen(fd) && fd->pMethods->iVersion>=3 ){ + sqlite3_int64 sz; + sz = pPager->szMmap; + pPager->bUseFetch = (sz>0); + setGetterMethod(pPager); + sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_SIZE, &sz); + } +#endif +} + +/* +** Change the maximum size of any memory mapping made of the database file. +*/ +void sqlite3PagerSetMmapLimit(Pager *pPager, sqlite3_int64 szMmap){ + pPager->szMmap = szMmap; + pagerFixMaplimit(pPager); +} + +/* +** Free as much memory as possible from the pager. +*/ +void sqlite3PagerShrink(Pager *pPager){ + sqlite3PcacheShrink(pPager->pPCache); +} + +/* +** Adjust settings of the pager to those specified in the pgFlags parameter. +** +** The "level" in pgFlags & PAGER_SYNCHRONOUS_MASK sets the robustness +** of the database to damage due to OS crashes or power failures by +** changing the number of syncs()s when writing the journals. +** There are four levels: +** +** OFF sqlite3OsSync() is never called. This is the default +** for temporary and transient files. +** +** NORMAL The journal is synced once before writes begin on the +** database. This is normally adequate protection, but +** it is theoretically possible, though very unlikely, +** that an inopertune power failure could leave the journal +** in a state which would cause damage to the database +** when it is rolled back. +** +** FULL The journal is synced twice before writes begin on the +** database (with some additional information - the nRec field +** of the journal header - being written in between the two +** syncs). If we assume that writing a +** single disk sector is atomic, then this mode provides +** assurance that the journal will not be corrupted to the +** point of causing damage to the database during rollback. +** +** EXTRA This is like FULL except that is also syncs the directory +** that contains the rollback journal after the rollback +** journal is unlinked. +** +** The above is for a rollback-journal mode. For WAL mode, OFF continues +** to mean that no syncs ever occur. NORMAL means that the WAL is synced +** prior to the start of checkpoint and that the database file is synced +** at the conclusion of the checkpoint if the entire content of the WAL +** was written back into the database. But no sync operations occur for +** an ordinary commit in NORMAL mode with WAL. FULL means that the WAL +** file is synced following each commit operation, in addition to the +** syncs associated with NORMAL. There is no difference between FULL +** and EXTRA for WAL mode. +** +** Do not confuse synchronous=FULL with SQLITE_SYNC_FULL. The +** SQLITE_SYNC_FULL macro means to use the MacOSX-style full-fsync +** using fcntl(F_FULLFSYNC). SQLITE_SYNC_NORMAL means to do an +** ordinary fsync() call. There is no difference between SQLITE_SYNC_FULL +** and SQLITE_SYNC_NORMAL on platforms other than MacOSX. But the +** synchronous=FULL versus synchronous=NORMAL setting determines when +** the xSync primitive is called and is relevant to all platforms. +** +** Numeric values associated with these states are OFF==1, NORMAL=2, +** and FULL=3. +*/ +void sqlite3PagerSetFlags( + Pager *pPager, /* The pager to set safety level for */ + unsigned pgFlags /* Various flags */ +){ + unsigned level = pgFlags & PAGER_SYNCHRONOUS_MASK; + if( pPager->tempFile ){ + pPager->noSync = 1; + pPager->fullSync = 0; + pPager->extraSync = 0; + }else{ + pPager->noSync = level==PAGER_SYNCHRONOUS_OFF ?1:0; + pPager->fullSync = level>=PAGER_SYNCHRONOUS_FULL ?1:0; + pPager->extraSync = level==PAGER_SYNCHRONOUS_EXTRA ?1:0; + } + if( pPager->noSync ){ + pPager->syncFlags = 0; + }else if( pgFlags & PAGER_FULLFSYNC ){ + pPager->syncFlags = SQLITE_SYNC_FULL; + }else{ + pPager->syncFlags = SQLITE_SYNC_NORMAL; + } + pPager->walSyncFlags = (pPager->syncFlags<<2); + if( pPager->fullSync ){ + pPager->walSyncFlags |= pPager->syncFlags; + } + if( (pgFlags & PAGER_CKPT_FULLFSYNC) && !pPager->noSync ){ + pPager->walSyncFlags |= (SQLITE_SYNC_FULL<<2); + } + if( pgFlags & PAGER_CACHESPILL ){ + pPager->doNotSpill &= ~SPILLFLAG_OFF; + }else{ + pPager->doNotSpill |= SPILLFLAG_OFF; + } +} + +/* +** The following global variable is incremented whenever the library +** attempts to open a temporary file. This information is used for +** testing and analysis only. +*/ +#ifdef SQLITE_TEST +int sqlite3_opentemp_count = 0; +#endif + +/* +** Open a temporary file. +** +** Write the file descriptor into *pFile. Return SQLITE_OK on success +** or some other error code if we fail. The OS will automatically +** delete the temporary file when it is closed. +** +** The flags passed to the VFS layer xOpen() call are those specified +** by parameter vfsFlags ORed with the following: +** +** SQLITE_OPEN_READWRITE +** SQLITE_OPEN_CREATE +** SQLITE_OPEN_EXCLUSIVE +** SQLITE_OPEN_DELETEONCLOSE +*/ +static int pagerOpentemp( + Pager *pPager, /* The pager object */ + sqlite3_file *pFile, /* Write the file descriptor here */ + int vfsFlags /* Flags passed through to the VFS */ +){ + int rc; /* Return code */ + +#ifdef SQLITE_TEST + sqlite3_opentemp_count++; /* Used for testing and analysis only */ +#endif + + vfsFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | + SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE; + rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0); + assert( rc!=SQLITE_OK || isOpen(pFile) ); + return rc; +} + +/* +** Set the busy handler function. +** +** The pager invokes the busy-handler if sqlite3OsLock() returns +** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock, +** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE +** lock. It does *not* invoke the busy handler when upgrading from +** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE +** (which occurs during hot-journal rollback). Summary: +** +** Transition | Invokes xBusyHandler +** -------------------------------------------------------- +** NO_LOCK -> SHARED_LOCK | Yes +** SHARED_LOCK -> RESERVED_LOCK | No +** SHARED_LOCK -> EXCLUSIVE_LOCK | No +** RESERVED_LOCK -> EXCLUSIVE_LOCK | Yes +** +** If the busy-handler callback returns non-zero, the lock is +** retried. If it returns zero, then the SQLITE_BUSY error is +** returned to the caller of the pager API function. +*/ +void sqlite3PagerSetBusyHandler( + Pager *pPager, /* Pager object */ + int (*xBusyHandler)(void *), /* Pointer to busy-handler function */ + void *pBusyHandlerArg /* Argument to pass to xBusyHandler */ +){ + void **ap; + pPager->xBusyHandler = xBusyHandler; + pPager->pBusyHandlerArg = pBusyHandlerArg; + ap = (void **)&pPager->xBusyHandler; + assert( ((int(*)(void *))(ap[0]))==xBusyHandler ); + assert( ap[1]==pBusyHandlerArg ); + sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_BUSYHANDLER, (void *)ap); +} + +/* +** Change the page size used by the Pager object. The new page size +** is passed in *pPageSize. +** +** If the pager is in the error state when this function is called, it +** is a no-op. The value returned is the error state error code (i.e. +** one of SQLITE_IOERR, an SQLITE_IOERR_xxx sub-code or SQLITE_FULL). +** +** Otherwise, if all of the following are true: +** +** * the new page size (value of *pPageSize) is valid (a power +** of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and +** +** * there are no outstanding page references, and +** +** * the database is either not an in-memory database or it is +** an in-memory database that currently consists of zero pages. +** +** then the pager object page size is set to *pPageSize. +** +** If the page size is changed, then this function uses sqlite3PagerMalloc() +** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt +** fails, SQLITE_NOMEM is returned and the page size remains unchanged. +** In all other cases, SQLITE_OK is returned. +** +** If the page size is not changed, either because one of the enumerated +** conditions above is not true, the pager was in error state when this +** function was called, or because the memory allocation attempt failed, +** then *pPageSize is set to the old, retained page size before returning. +*/ +int sqlite3PagerSetPagesize(Pager *pPager, u32 *pPageSize, int nReserve){ + int rc = SQLITE_OK; + + /* It is not possible to do a full assert_pager_state() here, as this + ** function may be called from within PagerOpen(), before the state + ** of the Pager object is internally consistent. + ** + ** At one point this function returned an error if the pager was in + ** PAGER_ERROR state. But since PAGER_ERROR state guarantees that + ** there is at least one outstanding page reference, this function + ** is a no-op for that case anyhow. + */ + + u32 pageSize = *pPageSize; + assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) ); + if( (pPager->memDb==0 || pPager->dbSize==0) + && sqlite3PcacheRefCount(pPager->pPCache)==0 + && pageSize && pageSize!=(u32)pPager->pageSize + ){ + char *pNew = NULL; /* New temp space */ + i64 nByte = 0; + + if( pPager->eState>PAGER_OPEN && isOpen(pPager->fd) ){ + rc = sqlite3OsFileSize(pPager->fd, &nByte); + } + if( rc==SQLITE_OK ){ + /* 8 bytes of zeroed overrun space is sufficient so that the b-tree + * cell header parser will never run off the end of the allocation */ + pNew = (char *)sqlite3PageMalloc(pageSize+8); + if( !pNew ){ + rc = SQLITE_NOMEM_BKPT; + }else{ + memset(pNew+pageSize, 0, 8); + } + } + + if( rc==SQLITE_OK ){ + pager_reset(pPager); + rc = sqlite3PcacheSetPageSize(pPager->pPCache, pageSize); + } + if( rc==SQLITE_OK ){ + sqlite3PageFree(pPager->pTmpSpace); + pPager->pTmpSpace = pNew; + pPager->dbSize = (Pgno)((nByte+pageSize-1)/pageSize); + pPager->pageSize = pageSize; + pPager->lckPgno = (Pgno)(PENDING_BYTE/pageSize) + 1; + }else{ + sqlite3PageFree(pNew); + } + } + + *pPageSize = pPager->pageSize; + if( rc==SQLITE_OK ){ + if( nReserve<0 ) nReserve = pPager->nReserve; + assert( nReserve>=0 && nReserve<1000 ); + pPager->nReserve = (i16)nReserve; + pagerFixMaplimit(pPager); + } + return rc; +} + +/* +** Return a pointer to the "temporary page" buffer held internally +** by the pager. This is a buffer that is big enough to hold the +** entire content of a database page. This buffer is used internally +** during rollback and will be overwritten whenever a rollback +** occurs. But other modules are free to use it too, as long as +** no rollbacks are happening. +*/ +void *sqlite3PagerTempSpace(Pager *pPager){ + return pPager->pTmpSpace; +} + +/* +** Attempt to set the maximum database page count if mxPage is positive. +** Make no changes if mxPage is zero or negative. And never reduce the +** maximum page count below the current size of the database. +** +** Regardless of mxPage, return the current maximum page count. +*/ +Pgno sqlite3PagerMaxPageCount(Pager *pPager, Pgno mxPage){ + if( mxPage>0 ){ + pPager->mxPgno = mxPage; + } + assert( pPager->eState!=PAGER_OPEN ); /* Called only by OP_MaxPgcnt */ + /* assert( pPager->mxPgno>=pPager->dbSize ); */ + /* OP_MaxPgcnt ensures that the parameter passed to this function is not + ** less than the total number of valid pages in the database. But this + ** may be less than Pager.dbSize, and so the assert() above is not valid */ + return pPager->mxPgno; +} + +/* +** The following set of routines are used to disable the simulated +** I/O error mechanism. These routines are used to avoid simulated +** errors in places where we do not care about errors. +** +** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops +** and generate no code. +*/ +#ifdef SQLITE_TEST +extern int sqlite3_io_error_pending; +extern int sqlite3_io_error_hit; +static int saved_cnt; +void disable_simulated_io_errors(void){ + saved_cnt = sqlite3_io_error_pending; + sqlite3_io_error_pending = -1; +} +void enable_simulated_io_errors(void){ + sqlite3_io_error_pending = saved_cnt; +} +#else +# define disable_simulated_io_errors() +# define enable_simulated_io_errors() +#endif + +/* +** Read the first N bytes from the beginning of the file into memory +** that pDest points to. +** +** If the pager was opened on a transient file (zFilename==""), or +** opened on a file less than N bytes in size, the output buffer is +** zeroed and SQLITE_OK returned. The rationale for this is that this +** function is used to read database headers, and a new transient or +** zero sized database has a header than consists entirely of zeroes. +** +** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered, +** the error code is returned to the caller and the contents of the +** output buffer undefined. +*/ +int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){ + int rc = SQLITE_OK; + memset(pDest, 0, N); + assert( isOpen(pPager->fd) || pPager->tempFile ); + + /* This routine is only called by btree immediately after creating + ** the Pager object. There has not been an opportunity to transition + ** to WAL mode yet. + */ + assert( !pagerUseWal(pPager) ); + + if( isOpen(pPager->fd) ){ + IOTRACE(("DBHDR %p 0 %d\n", pPager, N)) + rc = sqlite3OsRead(pPager->fd, pDest, N, 0); + if( rc==SQLITE_IOERR_SHORT_READ ){ + rc = SQLITE_OK; + } + } + return rc; +} + +/* +** This function may only be called when a read-transaction is open on +** the pager. It returns the total number of pages in the database. +** +** However, if the file is between 1 and <page-size> bytes in size, then +** this is considered a 1 page file. +*/ +void sqlite3PagerPagecount(Pager *pPager, int *pnPage){ + assert( pPager->eState>=PAGER_READER ); + assert( pPager->eState!=PAGER_WRITER_FINISHED ); + *pnPage = (int)pPager->dbSize; +} + + +/* +** Try to obtain a lock of type locktype on the database file. If +** a similar or greater lock is already held, this function is a no-op +** (returning SQLITE_OK immediately). +** +** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke +** the busy callback if the lock is currently not available. Repeat +** until the busy callback returns false or until the attempt to +** obtain the lock succeeds. +** +** Return SQLITE_OK on success and an error code if we cannot obtain +** the lock. If the lock is obtained successfully, set the Pager.state +** variable to locktype before returning. +*/ +static int pager_wait_on_lock(Pager *pPager, int locktype){ + int rc; /* Return code */ + + /* Check that this is either a no-op (because the requested lock is + ** already held), or one of the transitions that the busy-handler + ** may be invoked during, according to the comment above + ** sqlite3PagerSetBusyhandler(). + */ + assert( (pPager->eLock>=locktype) + || (pPager->eLock==NO_LOCK && locktype==SHARED_LOCK) + || (pPager->eLock==RESERVED_LOCK && locktype==EXCLUSIVE_LOCK) + ); + + do { + rc = pagerLockDb(pPager, locktype); + }while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) ); + return rc; +} + +/* +** Function assertTruncateConstraint(pPager) checks that one of the +** following is true for all dirty pages currently in the page-cache: +** +** a) The page number is less than or equal to the size of the +** current database image, in pages, OR +** +** b) if the page content were written at this time, it would not +** be necessary to write the current content out to the sub-journal. +** +** If the condition asserted by this function were not true, and the +** dirty page were to be discarded from the cache via the pagerStress() +** routine, pagerStress() would not write the current page content to +** the database file. If a savepoint transaction were rolled back after +** this happened, the correct behavior would be to restore the current +** content of the page. However, since this content is not present in either +** the database file or the portion of the rollback journal and +** sub-journal rolled back the content could not be restored and the +** database image would become corrupt. It is therefore fortunate that +** this circumstance cannot arise. +*/ +#if defined(SQLITE_DEBUG) +static void assertTruncateConstraintCb(PgHdr *pPg){ + Pager *pPager = pPg->pPager; + assert( pPg->flags&PGHDR_DIRTY ); + if( pPg->pgno>pPager->dbSize ){ /* if (a) is false */ + Pgno pgno = pPg->pgno; + int i; + for(i=0; i<pPg->pPager->nSavepoint; i++){ + PagerSavepoint *p = &pPager->aSavepoint[i]; + assert( p->nOrig<pgno || sqlite3BitvecTestNotNull(p->pInSavepoint,pgno) ); + } + } +} +static void assertTruncateConstraint(Pager *pPager){ + sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb); +} +#else +# define assertTruncateConstraint(pPager) +#endif + +/* +** Truncate the in-memory database file image to nPage pages. This +** function does not actually modify the database file on disk. It +** just sets the internal state of the pager object so that the +** truncation will be done when the current transaction is committed. +** +** This function is only called right before committing a transaction. +** Once this function has been called, the transaction must either be +** rolled back or committed. It is not safe to call this function and +** then continue writing to the database. +*/ +void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){ + assert( pPager->dbSize>=nPage || CORRUPT_DB ); + assert( pPager->eState>=PAGER_WRITER_CACHEMOD ); + pPager->dbSize = nPage; + + /* At one point the code here called assertTruncateConstraint() to + ** ensure that all pages being truncated away by this operation are, + ** if one or more savepoints are open, present in the savepoint + ** journal so that they can be restored if the savepoint is rolled + ** back. This is no longer necessary as this function is now only + ** called right before committing a transaction. So although the + ** Pager object may still have open savepoints (Pager.nSavepoint!=0), + ** they cannot be rolled back. So the assertTruncateConstraint() call + ** is no longer correct. */ +} + + +/* +** This function is called before attempting a hot-journal rollback. It +** syncs the journal file to disk, then sets pPager->journalHdr to the +** size of the journal file so that the pager_playback() routine knows +** that the entire journal file has been synced. +** +** Syncing a hot-journal to disk before attempting to roll it back ensures +** that if a power-failure occurs during the rollback, the process that +** attempts rollback following system recovery sees the same journal +** content as this process. +** +** If everything goes as planned, SQLITE_OK is returned. Otherwise, +** an SQLite error code. +*/ +static int pagerSyncHotJournal(Pager *pPager){ + int rc = SQLITE_OK; + if( !pPager->noSync ){ + rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL); + } + if( rc==SQLITE_OK ){ + rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr); + } + return rc; +} + +#if SQLITE_MAX_MMAP_SIZE>0 +/* +** Obtain a reference to a memory mapped page object for page number pgno. +** The new object will use the pointer pData, obtained from xFetch(). +** If successful, set *ppPage to point to the new page reference +** and return SQLITE_OK. Otherwise, return an SQLite error code and set +** *ppPage to zero. +** +** Page references obtained by calling this function should be released +** by calling pagerReleaseMapPage(). +*/ +static int pagerAcquireMapPage( + Pager *pPager, /* Pager object */ + Pgno pgno, /* Page number */ + void *pData, /* xFetch()'d data for this page */ + PgHdr **ppPage /* OUT: Acquired page object */ +){ + PgHdr *p; /* Memory mapped page to return */ + + if( pPager->pMmapFreelist ){ + *ppPage = p = pPager->pMmapFreelist; + pPager->pMmapFreelist = p->pDirty; + p->pDirty = 0; + assert( pPager->nExtra>=8 ); + memset(p->pExtra, 0, 8); + }else{ + *ppPage = p = (PgHdr *)sqlite3MallocZero(sizeof(PgHdr) + pPager->nExtra); + if( p==0 ){ + sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1) * pPager->pageSize, pData); + return SQLITE_NOMEM_BKPT; + } + p->pExtra = (void *)&p[1]; + p->flags = PGHDR_MMAP; + p->nRef = 1; + p->pPager = pPager; + } + + assert( p->pExtra==(void *)&p[1] ); + assert( p->pPage==0 ); + assert( p->flags==PGHDR_MMAP ); + assert( p->pPager==pPager ); + assert( p->nRef==1 ); + + p->pgno = pgno; + p->pData = pData; + pPager->nMmapOut++; + + return SQLITE_OK; +} +#endif + +/* +** Release a reference to page pPg. pPg must have been returned by an +** earlier call to pagerAcquireMapPage(). +*/ +static void pagerReleaseMapPage(PgHdr *pPg){ + Pager *pPager = pPg->pPager; + pPager->nMmapOut--; + pPg->pDirty = pPager->pMmapFreelist; + pPager->pMmapFreelist = pPg; + + assert( pPager->fd->pMethods->iVersion>=3 ); + sqlite3OsUnfetch(pPager->fd, (i64)(pPg->pgno-1)*pPager->pageSize, pPg->pData); +} + +/* +** Free all PgHdr objects stored in the Pager.pMmapFreelist list. +*/ +static void pagerFreeMapHdrs(Pager *pPager){ + PgHdr *p; + PgHdr *pNext; + for(p=pPager->pMmapFreelist; p; p=pNext){ + pNext = p->pDirty; + sqlite3_free(p); + } +} + +/* Verify that the database file has not be deleted or renamed out from +** under the pager. Return SQLITE_OK if the database is still where it ought +** to be on disk. Return non-zero (SQLITE_READONLY_DBMOVED or some other error +** code from sqlite3OsAccess()) if the database has gone missing. +*/ +static int databaseIsUnmoved(Pager *pPager){ + int bHasMoved = 0; + int rc; + + if( pPager->tempFile ) return SQLITE_OK; + if( pPager->dbSize==0 ) return SQLITE_OK; + assert( pPager->zFilename && pPager->zFilename[0] ); + rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_HAS_MOVED, &bHasMoved); + if( rc==SQLITE_NOTFOUND ){ + /* If the HAS_MOVED file-control is unimplemented, assume that the file + ** has not been moved. That is the historical behavior of SQLite: prior to + ** version 3.8.3, it never checked */ + rc = SQLITE_OK; + }else if( rc==SQLITE_OK && bHasMoved ){ + rc = SQLITE_READONLY_DBMOVED; + } + return rc; +} + + +/* +** Shutdown the page cache. Free all memory and close all files. +** +** If a transaction was in progress when this routine is called, that +** transaction is rolled back. All outstanding pages are invalidated +** and their memory is freed. Any attempt to use a page associated +** with this page cache after this function returns will likely +** result in a coredump. +** +** This function always succeeds. If a transaction is active an attempt +** is made to roll it back. If an error occurs during the rollback +** a hot journal may be left in the filesystem but no error is returned +** to the caller. +*/ +int sqlite3PagerClose(Pager *pPager, sqlite3 *db){ + u8 *pTmp = (u8*)pPager->pTmpSpace; + assert( db || pagerUseWal(pPager)==0 ); + assert( assert_pager_state(pPager) ); + disable_simulated_io_errors(); + sqlite3BeginBenignMalloc(); + pagerFreeMapHdrs(pPager); + /* pPager->errCode = 0; */ + pPager->exclusiveMode = 0; +#ifndef SQLITE_OMIT_WAL + { + u8 *a = 0; + assert( db || pPager->pWal==0 ); + if( db && 0==(db->flags & SQLITE_NoCkptOnClose) + && SQLITE_OK==databaseIsUnmoved(pPager) + ){ + a = pTmp; + } + sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags, pPager->pageSize,a); + pPager->pWal = 0; + } +#endif + pager_reset(pPager); + if( MEMDB ){ + pager_unlock(pPager); + }else{ + /* If it is open, sync the journal file before calling UnlockAndRollback. + ** If this is not done, then an unsynced portion of the open journal + ** file may be played back into the database. If a power failure occurs + ** while this is happening, the database could become corrupt. + ** + ** If an error occurs while trying to sync the journal, shift the pager + ** into the ERROR state. This causes UnlockAndRollback to unlock the + ** database and close the journal file without attempting to roll it + ** back or finalize it. The next database user will have to do hot-journal + ** rollback before accessing the database file. + */ + if( isOpen(pPager->jfd) ){ + pager_error(pPager, pagerSyncHotJournal(pPager)); + } + pagerUnlockAndRollback(pPager); + } + sqlite3EndBenignMalloc(); + enable_simulated_io_errors(); + PAGERTRACE(("CLOSE %d\n", PAGERID(pPager))); + IOTRACE(("CLOSE %p\n", pPager)) + sqlite3OsClose(pPager->jfd); + sqlite3OsClose(pPager->fd); + sqlite3PageFree(pTmp); + sqlite3PcacheClose(pPager->pPCache); + assert( !pPager->aSavepoint && !pPager->pInJournal ); + assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) ); + + sqlite3_free(pPager); + return SQLITE_OK; +} + +#if !defined(NDEBUG) || defined(SQLITE_TEST) +/* +** Return the page number for page pPg. +*/ +Pgno sqlite3PagerPagenumber(DbPage *pPg){ + return pPg->pgno; +} +#endif + +/* +** Increment the reference count for page pPg. +*/ +void sqlite3PagerRef(DbPage *pPg){ + sqlite3PcacheRef(pPg); +} + +/* +** Sync the journal. In other words, make sure all the pages that have +** been written to the journal have actually reached the surface of the +** disk and can be restored in the event of a hot-journal rollback. +** +** If the Pager.noSync flag is set, then this function is a no-op. +** Otherwise, the actions required depend on the journal-mode and the +** device characteristics of the file-system, as follows: +** +** * If the journal file is an in-memory journal file, no action need +** be taken. +** +** * Otherwise, if the device does not support the SAFE_APPEND property, +** then the nRec field of the most recently written journal header +** is updated to contain the number of journal records that have +** been written following it. If the pager is operating in full-sync +** mode, then the journal file is synced before this field is updated. +** +** * If the device does not support the SEQUENTIAL property, then +** journal file is synced. +** +** Or, in pseudo-code: +** +** if( NOT <in-memory journal> ){ +** if( NOT SAFE_APPEND ){ +** if( <full-sync mode> ) xSync(<journal file>); +** <update nRec field> +** } +** if( NOT SEQUENTIAL ) xSync(<journal file>); +** } +** +** If successful, this routine clears the PGHDR_NEED_SYNC flag of every +** page currently held in memory before returning SQLITE_OK. If an IO +** error is encountered, then the IO error code is returned to the caller. +*/ +static int syncJournal(Pager *pPager, int newHdr){ + int rc; /* Return code */ + + assert( pPager->eState==PAGER_WRITER_CACHEMOD + || pPager->eState==PAGER_WRITER_DBMOD + ); + assert( assert_pager_state(pPager) ); + assert( !pagerUseWal(pPager) ); + + rc = sqlite3PagerExclusiveLock(pPager); + if( rc!=SQLITE_OK ) return rc; + + if( !pPager->noSync ){ + assert( !pPager->tempFile ); + if( isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){ + const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd); + assert( isOpen(pPager->jfd) ); + + if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){ + /* This block deals with an obscure problem. If the last connection + ** that wrote to this database was operating in persistent-journal + ** mode, then the journal file may at this point actually be larger + ** than Pager.journalOff bytes. If the next thing in the journal + ** file happens to be a journal-header (written as part of the + ** previous connection's transaction), and a crash or power-failure + ** occurs after nRec is updated but before this connection writes + ** anything else to the journal file (or commits/rolls back its + ** transaction), then SQLite may become confused when doing the + ** hot-journal rollback following recovery. It may roll back all + ** of this connections data, then proceed to rolling back the old, + ** out-of-date data that follows it. Database corruption. + ** + ** To work around this, if the journal file does appear to contain + ** a valid header following Pager.journalOff, then write a 0x00 + ** byte to the start of it to prevent it from being recognized. + ** + ** Variable iNextHdrOffset is set to the offset at which this + ** problematic header will occur, if it exists. aMagic is used + ** as a temporary buffer to inspect the first couple of bytes of + ** the potential journal header. + */ + i64 iNextHdrOffset; + u8 aMagic[8]; + u8 zHeader[sizeof(aJournalMagic)+4]; + + memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic)); + put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec); + + iNextHdrOffset = journalHdrOffset(pPager); + rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset); + if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){ + static const u8 zerobyte = 0; + rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset); + } + if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){ + return rc; + } + + /* Write the nRec value into the journal file header. If in + ** full-synchronous mode, sync the journal first. This ensures that + ** all data has really hit the disk before nRec is updated to mark + ** it as a candidate for rollback. + ** + ** This is not required if the persistent media supports the + ** SAFE_APPEND property. Because in this case it is not possible + ** for garbage data to be appended to the file, the nRec field + ** is populated with 0xFFFFFFFF when the journal header is written + ** and never needs to be updated. + */ + if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){ + PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager))); + IOTRACE(("JSYNC %p\n", pPager)) + rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags); + if( rc!=SQLITE_OK ) return rc; + } + IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr)); + rc = sqlite3OsWrite( + pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr + ); + if( rc!=SQLITE_OK ) return rc; + } + if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){ + PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager))); + IOTRACE(("JSYNC %p\n", pPager)) + rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags| + (pPager->syncFlags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0) + ); + if( rc!=SQLITE_OK ) return rc; + } + + pPager->journalHdr = pPager->journalOff; + if( newHdr && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){ + pPager->nRec = 0; + rc = writeJournalHdr(pPager); + if( rc!=SQLITE_OK ) return rc; + } + }else{ + pPager->journalHdr = pPager->journalOff; + } + } + + /* Unless the pager is in noSync mode, the journal file was just + ** successfully synced. Either way, clear the PGHDR_NEED_SYNC flag on + ** all pages. + */ + sqlite3PcacheClearSyncFlags(pPager->pPCache); + pPager->eState = PAGER_WRITER_DBMOD; + assert( assert_pager_state(pPager) ); + return SQLITE_OK; +} + +/* +** The argument is the first in a linked list of dirty pages connected +** by the PgHdr.pDirty pointer. This function writes each one of the +** in-memory pages in the list to the database file. The argument may +** be NULL, representing an empty list. In this case this function is +** a no-op. +** +** The pager must hold at least a RESERVED lock when this function +** is called. Before writing anything to the database file, this lock +** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained, +** SQLITE_BUSY is returned and no data is written to the database file. +** +** If the pager is a temp-file pager and the actual file-system file +** is not yet open, it is created and opened before any data is +** written out. +** +** Once the lock has been upgraded and, if necessary, the file opened, +** the pages are written out to the database file in list order. Writing +** a page is skipped if it meets either of the following criteria: +** +** * The page number is greater than Pager.dbSize, or +** * The PGHDR_DONT_WRITE flag is set on the page. +** +** If writing out a page causes the database file to grow, Pager.dbFileSize +** is updated accordingly. If page 1 is written out, then the value cached +** in Pager.dbFileVers[] is updated to match the new value stored in +** the database file. +** +** If everything is successful, SQLITE_OK is returned. If an IO error +** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot +** be obtained, SQLITE_BUSY is returned. +*/ +static int pager_write_pagelist(Pager *pPager, PgHdr *pList){ + int rc = SQLITE_OK; /* Return code */ + + /* This function is only called for rollback pagers in WRITER_DBMOD state. */ + assert( !pagerUseWal(pPager) ); + assert( pPager->tempFile || pPager->eState==PAGER_WRITER_DBMOD ); + assert( pPager->eLock==EXCLUSIVE_LOCK ); + assert( isOpen(pPager->fd) || pList->pDirty==0 ); + + /* If the file is a temp-file has not yet been opened, open it now. It + ** is not possible for rc to be other than SQLITE_OK if this branch + ** is taken, as pager_wait_on_lock() is a no-op for temp-files. + */ + if( !isOpen(pPager->fd) ){ + assert( pPager->tempFile && rc==SQLITE_OK ); + rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags); + } + + /* Before the first write, give the VFS a hint of what the final + ** file size will be. + */ + assert( rc!=SQLITE_OK || isOpen(pPager->fd) ); + if( rc==SQLITE_OK + && pPager->dbHintSize<pPager->dbSize + && (pList->pDirty || pList->pgno>pPager->dbHintSize) + ){ + sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize; + sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile); + pPager->dbHintSize = pPager->dbSize; + } + + while( rc==SQLITE_OK && pList ){ + Pgno pgno = pList->pgno; + + /* If there are dirty pages in the page cache with page numbers greater + ** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to + ** make the file smaller (presumably by auto-vacuum code). Do not write + ** any such pages to the file. + ** + ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag + ** set (set by sqlite3PagerDontWrite()). + */ + if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){ + i64 offset = (pgno-1)*(i64)pPager->pageSize; /* Offset to write */ + char *pData; /* Data to write */ + + assert( (pList->flags&PGHDR_NEED_SYNC)==0 ); + if( pList->pgno==1 ) pager_write_changecounter(pList); + + pData = pList->pData; + + /* Write out the page data. */ + rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset); + + /* If page 1 was just written, update Pager.dbFileVers to match + ** the value now stored in the database file. If writing this + ** page caused the database file to grow, update dbFileSize. + */ + if( pgno==1 ){ + memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers)); + } + if( pgno>pPager->dbFileSize ){ + pPager->dbFileSize = pgno; + } + pPager->aStat[PAGER_STAT_WRITE]++; + + /* Update any backup objects copying the contents of this pager. */ + sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)pList->pData); + + PAGERTRACE(("STORE %d page %d hash(%08x)\n", + PAGERID(pPager), pgno, pager_pagehash(pList))); + IOTRACE(("PGOUT %p %d\n", pPager, pgno)); + PAGER_INCR(sqlite3_pager_writedb_count); + }else{ + PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno)); + } + pager_set_pagehash(pList); + pList = pList->pDirty; + } + + return rc; +} + +/* +** Ensure that the sub-journal file is open. If it is already open, this +** function is a no-op. +** +** SQLITE_OK is returned if everything goes according to plan. An +** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen() +** fails. +*/ +static int openSubJournal(Pager *pPager){ + int rc = SQLITE_OK; + if( !isOpen(pPager->sjfd) ){ + const int flags = SQLITE_OPEN_SUBJOURNAL | SQLITE_OPEN_READWRITE + | SQLITE_OPEN_CREATE | SQLITE_OPEN_EXCLUSIVE + | SQLITE_OPEN_DELETEONCLOSE; + int nStmtSpill = sqlite3Config.nStmtSpill; + if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){ + nStmtSpill = -1; + } + rc = sqlite3JournalOpen(pPager->pVfs, 0, pPager->sjfd, flags, nStmtSpill); + } + return rc; +} + +/* +** Append a record of the current state of page pPg to the sub-journal. +** +** If successful, set the bit corresponding to pPg->pgno in the bitvecs +** for all open savepoints before returning. +** +** This function returns SQLITE_OK if everything is successful, an IO +** error code if the attempt to write to the sub-journal fails, or +** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint +** bitvec. +*/ +static int subjournalPage(PgHdr *pPg){ + int rc = SQLITE_OK; + Pager *pPager = pPg->pPager; + if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){ + + /* Open the sub-journal, if it has not already been opened */ + assert( pPager->useJournal ); + assert( isOpen(pPager->jfd) || pagerUseWal(pPager) ); + assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 ); + assert( pagerUseWal(pPager) + || pageInJournal(pPager, pPg) + || pPg->pgno>pPager->dbOrigSize + ); + rc = openSubJournal(pPager); + + /* If the sub-journal was opened successfully (or was already open), + ** write the journal record into the file. */ + if( rc==SQLITE_OK ){ + void *pData = pPg->pData; + i64 offset = (i64)pPager->nSubRec*(4+pPager->pageSize); + char *pData2; + pData2 = pData; + PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno)); + rc = write32bits(pPager->sjfd, offset, pPg->pgno); + if( rc==SQLITE_OK ){ + rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4); + } + } + } + if( rc==SQLITE_OK ){ + pPager->nSubRec++; + assert( pPager->nSavepoint>0 ); + rc = addToSavepointBitvecs(pPager, pPg->pgno); + } + return rc; +} +static int subjournalPageIfRequired(PgHdr *pPg){ + if( subjRequiresPage(pPg) ){ + return subjournalPage(pPg); + }else{ + return SQLITE_OK; + } +} + +/* +** This function is called by the pcache layer when it has reached some +** soft memory limit. The first argument is a pointer to a Pager object +** (cast as a void*). The pager is always 'purgeable' (not an in-memory +** database). The second argument is a reference to a page that is +** currently dirty but has no outstanding references. The page +** is always associated with the Pager object passed as the first +** argument. +** +** The job of this function is to make pPg clean by writing its contents +** out to the database file, if possible. This may involve syncing the +** journal file. +** +** If successful, sqlite3PcacheMakeClean() is called on the page and +** SQLITE_OK returned. If an IO error occurs while trying to make the +** page clean, the IO error code is returned. If the page cannot be +** made clean for some other reason, but no error occurs, then SQLITE_OK +** is returned by sqlite3PcacheMakeClean() is not called. +*/ +static int pagerStress(void *p, PgHdr *pPg){ + Pager *pPager = (Pager *)p; + int rc = SQLITE_OK; + + assert( pPg->pPager==pPager ); + assert( pPg->flags&PGHDR_DIRTY ); + + /* The doNotSpill NOSYNC bit is set during times when doing a sync of + ** journal (and adding a new header) is not allowed. This occurs + ** during calls to sqlite3PagerWrite() while trying to journal multiple + ** pages belonging to the same sector. + ** + ** The doNotSpill ROLLBACK and OFF bits inhibits all cache spilling + ** regardless of whether or not a sync is required. This is set during + ** a rollback or by user request, respectively. + ** + ** Spilling is also prohibited when in an error state since that could + ** lead to database corruption. In the current implementation it + ** is impossible for sqlite3PcacheFetch() to be called with createFlag==3 + ** while in the error state, hence it is impossible for this routine to + ** be called in the error state. Nevertheless, we include a NEVER() + ** test for the error state as a safeguard against future changes. + */ + if( NEVER(pPager->errCode) ) return SQLITE_OK; + testcase( pPager->doNotSpill & SPILLFLAG_ROLLBACK ); + testcase( pPager->doNotSpill & SPILLFLAG_OFF ); + testcase( pPager->doNotSpill & SPILLFLAG_NOSYNC ); + if( pPager->doNotSpill + && ((pPager->doNotSpill & (SPILLFLAG_ROLLBACK|SPILLFLAG_OFF))!=0 + || (pPg->flags & PGHDR_NEED_SYNC)!=0) + ){ + return SQLITE_OK; + } + + pPager->aStat[PAGER_STAT_SPILL]++; + pPg->pDirty = 0; + if( pagerUseWal(pPager) ){ + /* Write a single frame for this page to the log. */ + rc = subjournalPageIfRequired(pPg); + if( rc==SQLITE_OK ){ + rc = pagerWalFrames(pPager, pPg, 0, 0); + } + }else{ + +#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE + if( pPager->tempFile==0 ){ + rc = sqlite3JournalCreate(pPager->jfd); + if( rc!=SQLITE_OK ) return pager_error(pPager, rc); + } +#endif + + /* Sync the journal file if required. */ + if( pPg->flags&PGHDR_NEED_SYNC + || pPager->eState==PAGER_WRITER_CACHEMOD + ){ + rc = syncJournal(pPager, 1); + } + + /* Write the contents of the page out to the database file. */ + if( rc==SQLITE_OK ){ + assert( (pPg->flags&PGHDR_NEED_SYNC)==0 ); + rc = pager_write_pagelist(pPager, pPg); + } + } + + /* Mark the page as clean. */ + if( rc==SQLITE_OK ){ + PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno)); + sqlite3PcacheMakeClean(pPg); + } + + return pager_error(pPager, rc); +} + +/* +** Flush all unreferenced dirty pages to disk. +*/ +int sqlite3PagerFlush(Pager *pPager){ + int rc = pPager->errCode; + if( !MEMDB ){ + PgHdr *pList = sqlite3PcacheDirtyList(pPager->pPCache); + assert( assert_pager_state(pPager) ); + while( rc==SQLITE_OK && pList ){ + PgHdr *pNext = pList->pDirty; + if( pList->nRef==0 ){ + rc = pagerStress((void*)pPager, pList); + } + pList = pNext; + } + } + + return rc; +} + +/* +** Allocate and initialize a new Pager object and put a pointer to it +** in *ppPager. The pager should eventually be freed by passing it +** to sqlite3PagerClose(). +** +** The zFilename argument is the path to the database file to open. +** If zFilename is NULL then a randomly-named temporary file is created +** and used as the file to be cached. Temporary files are be deleted +** automatically when they are closed. If zFilename is ":memory:" then +** all information is held in cache. It is never written to disk. +** This can be used to implement an in-memory database. +** +** The nExtra parameter specifies the number of bytes of space allocated +** along with each page reference. This space is available to the user +** via the sqlite3PagerGetExtra() API. When a new page is allocated, the +** first 8 bytes of this space are zeroed but the remainder is uninitialized. +** (The extra space is used by btree as the MemPage object.) +** +** The flags argument is used to specify properties that affect the +** operation of the pager. It should be passed some bitwise combination +** of the PAGER_* flags. +** +** The vfsFlags parameter is a bitmask to pass to the flags parameter +** of the xOpen() method of the supplied VFS when opening files. +** +** If the pager object is allocated and the specified file opened +** successfully, SQLITE_OK is returned and *ppPager set to point to +** the new pager object. If an error occurs, *ppPager is set to NULL +** and error code returned. This function may return SQLITE_NOMEM +** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or +** various SQLITE_IO_XXX errors. +*/ +int sqlite3PagerOpen( + sqlite3_vfs *pVfs, /* The virtual file system to use */ + Pager **ppPager, /* OUT: Return the Pager structure here */ + const char *zFilename, /* Name of the database file to open */ + int nExtra, /* Extra bytes append to each in-memory page */ + int flags, /* flags controlling this file */ + int vfsFlags, /* flags passed through to sqlite3_vfs.xOpen() */ + void (*xReinit)(DbPage*) /* Function to reinitialize pages */ +){ + u8 *pPtr; + Pager *pPager = 0; /* Pager object to allocate and return */ + int rc = SQLITE_OK; /* Return code */ + int tempFile = 0; /* True for temp files (incl. in-memory files) */ + int memDb = 0; /* True if this is an in-memory file */ + int memJM = 0; /* Memory journal mode */ + int readOnly = 0; /* True if this is a read-only file */ + int journalFileSize; /* Bytes to allocate for each journal fd */ + char *zPathname = 0; /* Full path to database file */ + int nPathname = 0; /* Number of bytes in zPathname */ + int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */ + int pcacheSize = sqlite3PcacheSize(); /* Bytes to allocate for PCache */ + u32 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE; /* Default page size */ + const char *zUri = 0; /* URI args to copy */ + int nUriByte = 1; /* Number of bytes of URI args at *zUri */ + + /* Figure out how much space is required for each journal file-handle + ** (there are two of them, the main journal and the sub-journal). */ + journalFileSize = ROUND8(sqlite3JournalSize(pVfs)); + + /* Set the output variable to NULL in case an error occurs. */ + *ppPager = 0; + +#ifndef SQLITE_OMIT_MEMORYDB + if( flags & PAGER_MEMORY ){ + memDb = 1; + if( zFilename && zFilename[0] ){ + zPathname = sqlite3DbStrDup(0, zFilename); + if( zPathname==0 ) return SQLITE_NOMEM_BKPT; + nPathname = sqlite3Strlen30(zPathname); + zFilename = 0; + } + } +#endif + + /* Compute and store the full pathname in an allocated buffer pointed + ** to by zPathname, length nPathname. Or, if this is a temporary file, + ** leave both nPathname and zPathname set to 0. + */ + if( zFilename && zFilename[0] ){ + const char *z; + nPathname = pVfs->mxPathname+1; + zPathname = sqlite3DbMallocRaw(0, nPathname*2); + if( zPathname==0 ){ + return SQLITE_NOMEM_BKPT; + } + zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */ + rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname); + if( rc!=SQLITE_OK ){ + if( rc==SQLITE_OK_SYMLINK ){ + if( vfsFlags & SQLITE_OPEN_NOFOLLOW ){ + rc = SQLITE_CANTOPEN_SYMLINK; + }else{ + rc = SQLITE_OK; + } + } + } + nPathname = sqlite3Strlen30(zPathname); + z = zUri = &zFilename[sqlite3Strlen30(zFilename)+1]; + while( *z ){ + z += strlen(z)+1; + z += strlen(z)+1; + } + nUriByte = (int)(&z[1] - zUri); + assert( nUriByte>=1 ); + if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){ + /* This branch is taken when the journal path required by + ** the database being opened will be more than pVfs->mxPathname + ** bytes in length. This means the database cannot be opened, + ** as it will not be possible to open the journal file or even + ** check for a hot-journal before reading. + */ + rc = SQLITE_CANTOPEN_BKPT; + } + if( rc!=SQLITE_OK ){ + sqlite3DbFree(0, zPathname); + return rc; + } + } + + /* Allocate memory for the Pager structure, PCache object, the + ** three file descriptors, the database file name and the journal + ** file name. The layout in memory is as follows: + ** + ** Pager object (sizeof(Pager) bytes) + ** PCache object (sqlite3PcacheSize() bytes) + ** Database file handle (pVfs->szOsFile bytes) + ** Sub-journal file handle (journalFileSize bytes) + ** Main journal file handle (journalFileSize bytes) + ** Ptr back to the Pager (sizeof(Pager*) bytes) + ** \0\0\0\0 database prefix (4 bytes) + ** Database file name (nPathname+1 bytes) + ** URI query parameters (nUriByte bytes) + ** Journal filename (nPathname+8+1 bytes) + ** WAL filename (nPathname+4+1 bytes) + ** \0\0\0 terminator (3 bytes) + ** + ** Some 3rd-party software, over which we have no control, depends on + ** the specific order of the filenames and the \0 separators between them + ** so that it can (for example) find the database filename given the WAL + ** filename without using the sqlite3_filename_database() API. This is a + ** misuse of SQLite and a bug in the 3rd-party software, but the 3rd-party + ** software is in widespread use, so we try to avoid changing the filename + ** order and formatting if possible. In particular, the details of the + ** filename format expected by 3rd-party software should be as follows: + ** + ** - Main Database Path + ** - \0 + ** - Multiple URI components consisting of: + ** - Key + ** - \0 + ** - Value + ** - \0 + ** - \0 + ** - Journal Path + ** - \0 + ** - WAL Path (zWALName) + ** - \0 + ** + ** The sqlite3_create_filename() interface and the databaseFilename() utility + ** that is used by sqlite3_filename_database() and kin also depend on the + ** specific formatting and order of the various filenames, so if the format + ** changes here, be sure to change it there as well. + */ + assert( SQLITE_PTRSIZE==sizeof(Pager*) ); + pPtr = (u8 *)sqlite3MallocZero( + ROUND8(sizeof(*pPager)) + /* Pager structure */ + ROUND8(pcacheSize) + /* PCache object */ + ROUND8(pVfs->szOsFile) + /* The main db file */ + journalFileSize * 2 + /* The two journal files */ + SQLITE_PTRSIZE + /* Space to hold a pointer */ + 4 + /* Database prefix */ + nPathname + 1 + /* database filename */ + nUriByte + /* query parameters */ + nPathname + 8 + 1 + /* Journal filename */ +#ifndef SQLITE_OMIT_WAL + nPathname + 4 + 1 + /* WAL filename */ +#endif + 3 /* Terminator */ + ); + assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) ); + if( !pPtr ){ + sqlite3DbFree(0, zPathname); + return SQLITE_NOMEM_BKPT; + } + pPager = (Pager*)pPtr; pPtr += ROUND8(sizeof(*pPager)); + pPager->pPCache = (PCache*)pPtr; pPtr += ROUND8(pcacheSize); + pPager->fd = (sqlite3_file*)pPtr; pPtr += ROUND8(pVfs->szOsFile); + pPager->sjfd = (sqlite3_file*)pPtr; pPtr += journalFileSize; + pPager->jfd = (sqlite3_file*)pPtr; pPtr += journalFileSize; + assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) ); + memcpy(pPtr, &pPager, SQLITE_PTRSIZE); pPtr += SQLITE_PTRSIZE; + + /* Fill in the Pager.zFilename and pPager.zQueryParam fields */ + pPtr += 4; /* Skip zero prefix */ + pPager->zFilename = (char*)pPtr; + if( nPathname>0 ){ + memcpy(pPtr, zPathname, nPathname); pPtr += nPathname + 1; + if( zUri ){ + memcpy(pPtr, zUri, nUriByte); pPtr += nUriByte; + }else{ + pPtr++; + } + } + + + /* Fill in Pager.zJournal */ + if( nPathname>0 ){ + pPager->zJournal = (char*)pPtr; + memcpy(pPtr, zPathname, nPathname); pPtr += nPathname; + memcpy(pPtr, "-journal",8); pPtr += 8 + 1; +#ifdef SQLITE_ENABLE_8_3_NAMES + sqlite3FileSuffix3(zFilename,pPager->zJournal); + pPtr = (u8*)(pPager->zJournal + sqlite3Strlen30(pPager->zJournal)+1); +#endif + }else{ + pPager->zJournal = 0; + } + +#ifndef SQLITE_OMIT_WAL + /* Fill in Pager.zWal */ + if( nPathname>0 ){ + pPager->zWal = (char*)pPtr; + memcpy(pPtr, zPathname, nPathname); pPtr += nPathname; + memcpy(pPtr, "-wal", 4); pPtr += 4 + 1; +#ifdef SQLITE_ENABLE_8_3_NAMES + sqlite3FileSuffix3(zFilename, pPager->zWal); + pPtr = (u8*)(pPager->zWal + sqlite3Strlen30(pPager->zWal)+1); +#endif + }else{ + pPager->zWal = 0; + } +#endif + (void)pPtr; /* Suppress warning about unused pPtr value */ + + if( nPathname ) sqlite3DbFree(0, zPathname); + pPager->pVfs = pVfs; + pPager->vfsFlags = vfsFlags; + + /* Open the pager file. + */ + if( zFilename && zFilename[0] ){ + int fout = 0; /* VFS flags returned by xOpen() */ + rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout); + assert( !memDb ); + pPager->memVfs = memJM = (fout&SQLITE_OPEN_MEMORY)!=0; + readOnly = (fout&SQLITE_OPEN_READONLY)!=0; + + /* If the file was successfully opened for read/write access, + ** choose a default page size in case we have to create the + ** database file. The default page size is the maximum of: + ** + ** + SQLITE_DEFAULT_PAGE_SIZE, + ** + The value returned by sqlite3OsSectorSize() + ** + The largest page size that can be written atomically. + */ + if( rc==SQLITE_OK ){ + int iDc = sqlite3OsDeviceCharacteristics(pPager->fd); + if( !readOnly ){ + setSectorSize(pPager); + assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE); + if( szPageDflt<pPager->sectorSize ){ + if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){ + szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE; + }else{ + szPageDflt = (u32)pPager->sectorSize; + } + } +#ifdef SQLITE_ENABLE_ATOMIC_WRITE + { + int ii; + assert(SQLITE_IOCAP_ATOMIC512==(512>>8)); + assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8)); + assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536); + for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){ + if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){ + szPageDflt = ii; + } + } + } +#endif + } + pPager->noLock = sqlite3_uri_boolean(pPager->zFilename, "nolock", 0); + if( (iDc & SQLITE_IOCAP_IMMUTABLE)!=0 + || sqlite3_uri_boolean(pPager->zFilename, "immutable", 0) ){ + vfsFlags |= SQLITE_OPEN_READONLY; + goto act_like_temp_file; + } + } + }else{ + /* If a temporary file is requested, it is not opened immediately. + ** In this case we accept the default page size and delay actually + ** opening the file until the first call to OsWrite(). + ** + ** This branch is also run for an in-memory database. An in-memory + ** database is the same as a temp-file that is never written out to + ** disk and uses an in-memory rollback journal. + ** + ** This branch also runs for files marked as immutable. + */ +act_like_temp_file: + tempFile = 1; + pPager->eState = PAGER_READER; /* Pretend we already have a lock */ + pPager->eLock = EXCLUSIVE_LOCK; /* Pretend we are in EXCLUSIVE mode */ + pPager->noLock = 1; /* Do no locking */ + readOnly = (vfsFlags&SQLITE_OPEN_READONLY); + } + + /* The following call to PagerSetPagesize() serves to set the value of + ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer. + */ + if( rc==SQLITE_OK ){ + assert( pPager->memDb==0 ); + rc = sqlite3PagerSetPagesize(pPager, &szPageDflt, -1); + testcase( rc!=SQLITE_OK ); + } + + /* Initialize the PCache object. */ + if( rc==SQLITE_OK ){ + nExtra = ROUND8(nExtra); + assert( nExtra>=8 && nExtra<1000 ); + rc = sqlite3PcacheOpen(szPageDflt, nExtra, !memDb, + !memDb?pagerStress:0, (void *)pPager, pPager->pPCache); + } + + /* If an error occurred above, free the Pager structure and close the file. + */ + if( rc!=SQLITE_OK ){ + sqlite3OsClose(pPager->fd); + sqlite3PageFree(pPager->pTmpSpace); + sqlite3_free(pPager); + return rc; + } + + PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename)); + IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename)) + + pPager->useJournal = (u8)useJournal; + /* pPager->stmtOpen = 0; */ + /* pPager->stmtInUse = 0; */ + /* pPager->nRef = 0; */ + /* pPager->stmtSize = 0; */ + /* pPager->stmtJSize = 0; */ + /* pPager->nPage = 0; */ + pPager->mxPgno = SQLITE_MAX_PAGE_COUNT; + /* pPager->state = PAGER_UNLOCK; */ + /* pPager->errMask = 0; */ + pPager->tempFile = (u8)tempFile; + assert( tempFile==PAGER_LOCKINGMODE_NORMAL + || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE ); + assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 ); + pPager->exclusiveMode = (u8)tempFile; + pPager->changeCountDone = pPager->tempFile; + pPager->memDb = (u8)memDb; + pPager->readOnly = (u8)readOnly; + assert( useJournal || pPager->tempFile ); + sqlite3PagerSetFlags(pPager, (SQLITE_DEFAULT_SYNCHRONOUS+1)|PAGER_CACHESPILL); + /* pPager->pFirst = 0; */ + /* pPager->pFirstSynced = 0; */ + /* pPager->pLast = 0; */ + pPager->nExtra = (u16)nExtra; + pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT; + assert( isOpen(pPager->fd) || tempFile ); + setSectorSize(pPager); + if( !useJournal ){ + pPager->journalMode = PAGER_JOURNALMODE_OFF; + }else if( memDb || memJM ){ + pPager->journalMode = PAGER_JOURNALMODE_MEMORY; + } + /* pPager->xBusyHandler = 0; */ + /* pPager->pBusyHandlerArg = 0; */ + pPager->xReiniter = xReinit; + setGetterMethod(pPager); + /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */ + /* pPager->szMmap = SQLITE_DEFAULT_MMAP_SIZE // will be set by btree.c */ + + *ppPager = pPager; + return SQLITE_OK; +} + +/* +** Return the sqlite3_file for the main database given the name +** of the corresponding WAL or Journal name as passed into +** xOpen. +*/ +sqlite3_file *sqlite3_database_file_object(const char *zName){ + Pager *pPager; + const char *p; + while( zName[-1]!=0 || zName[-2]!=0 || zName[-3]!=0 || zName[-4]!=0 ){ + zName--; + } + p = zName - 4 - sizeof(Pager*); + assert( EIGHT_BYTE_ALIGNMENT(p) ); + pPager = *(Pager**)p; + return pPager->fd; +} + + +/* +** This function is called after transitioning from PAGER_UNLOCK to +** PAGER_SHARED state. It tests if there is a hot journal present in +** the file-system for the given pager. A hot journal is one that +** needs to be played back. According to this function, a hot-journal +** file exists if the following criteria are met: +** +** * The journal file exists in the file system, and +** * No process holds a RESERVED or greater lock on the database file, and +** * The database file itself is greater than 0 bytes in size, and +** * The first byte of the journal file exists and is not 0x00. +** +** If the current size of the database file is 0 but a journal file +** exists, that is probably an old journal left over from a prior +** database with the same name. In this case the journal file is +** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK +** is returned. +** +** This routine does not check if there is a super-journal filename +** at the end of the file. If there is, and that super-journal file +** does not exist, then the journal file is not really hot. In this +** case this routine will return a false-positive. The pager_playback() +** routine will discover that the journal file is not really hot and +** will not roll it back. +** +** If a hot-journal file is found to exist, *pExists is set to 1 and +** SQLITE_OK returned. If no hot-journal file is present, *pExists is +** set to 0 and SQLITE_OK returned. If an IO error occurs while trying +** to determine whether or not a hot-journal file exists, the IO error +** code is returned and the value of *pExists is undefined. +*/ +static int hasHotJournal(Pager *pPager, int *pExists){ + sqlite3_vfs * const pVfs = pPager->pVfs; + int rc = SQLITE_OK; /* Return code */ + int exists = 1; /* True if a journal file is present */ + int jrnlOpen = !!isOpen(pPager->jfd); + + assert( pPager->useJournal ); + assert( isOpen(pPager->fd) ); + assert( pPager->eState==PAGER_OPEN ); + + assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) & + SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN + )); + + *pExists = 0; + if( !jrnlOpen ){ + rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists); + } + if( rc==SQLITE_OK && exists ){ + int locked = 0; /* True if some process holds a RESERVED lock */ + + /* Race condition here: Another process might have been holding the + ** the RESERVED lock and have a journal open at the sqlite3OsAccess() + ** call above, but then delete the journal and drop the lock before + ** we get to the following sqlite3OsCheckReservedLock() call. If that + ** is the case, this routine might think there is a hot journal when + ** in fact there is none. This results in a false-positive which will + ** be dealt with by the playback routine. Ticket #3883. + */ + rc = sqlite3OsCheckReservedLock(pPager->fd, &locked); + if( rc==SQLITE_OK && !locked ){ + Pgno nPage; /* Number of pages in database file */ + + assert( pPager->tempFile==0 ); + rc = pagerPagecount(pPager, &nPage); + if( rc==SQLITE_OK ){ + /* If the database is zero pages in size, that means that either (1) the + ** journal is a remnant from a prior database with the same name where + ** the database file but not the journal was deleted, or (2) the initial + ** transaction that populates a new database is being rolled back. + ** In either case, the journal file can be deleted. However, take care + ** not to delete the journal file if it is already open due to + ** journal_mode=PERSIST. + */ + if( nPage==0 && !jrnlOpen ){ + sqlite3BeginBenignMalloc(); + if( pagerLockDb(pPager, RESERVED_LOCK)==SQLITE_OK ){ + sqlite3OsDelete(pVfs, pPager->zJournal, 0); + if( !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK); + } + sqlite3EndBenignMalloc(); + }else{ + /* The journal file exists and no other connection has a reserved + ** or greater lock on the database file. Now check that there is + ** at least one non-zero bytes at the start of the journal file. + ** If there is, then we consider this journal to be hot. If not, + ** it can be ignored. + */ + if( !jrnlOpen ){ + int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL; + rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f); + } + if( rc==SQLITE_OK ){ + u8 first = 0; + rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0); + if( rc==SQLITE_IOERR_SHORT_READ ){ + rc = SQLITE_OK; + } + if( !jrnlOpen ){ + sqlite3OsClose(pPager->jfd); + } + *pExists = (first!=0); + }else if( rc==SQLITE_CANTOPEN ){ + /* If we cannot open the rollback journal file in order to see if + ** it has a zero header, that might be due to an I/O error, or + ** it might be due to the race condition described above and in + ** ticket #3883. Either way, assume that the journal is hot. + ** This might be a false positive. But if it is, then the + ** automatic journal playback and recovery mechanism will deal + ** with it under an EXCLUSIVE lock where we do not need to + ** worry so much with race conditions. + */ + *pExists = 1; + rc = SQLITE_OK; + } + } + } + } + } + + return rc; +} + +/* +** This function is called to obtain a shared lock on the database file. +** It is illegal to call sqlite3PagerGet() until after this function +** has been successfully called. If a shared-lock is already held when +** this function is called, it is a no-op. +** +** The following operations are also performed by this function. +** +** 1) If the pager is currently in PAGER_OPEN state (no lock held +** on the database file), then an attempt is made to obtain a +** SHARED lock on the database file. Immediately after obtaining +** the SHARED lock, the file-system is checked for a hot-journal, +** which is played back if present. Following any hot-journal +** rollback, the contents of the cache are validated by checking +** the 'change-counter' field of the database file header and +** discarded if they are found to be invalid. +** +** 2) If the pager is running in exclusive-mode, and there are currently +** no outstanding references to any pages, and is in the error state, +** then an attempt is made to clear the error state by discarding +** the contents of the page cache and rolling back any open journal +** file. +** +** If everything is successful, SQLITE_OK is returned. If an IO error +** occurs while locking the database, checking for a hot-journal file or +** rolling back a journal file, the IO error code is returned. +*/ +int sqlite3PagerSharedLock(Pager *pPager){ + int rc = SQLITE_OK; /* Return code */ + + /* This routine is only called from b-tree and only when there are no + ** outstanding pages. This implies that the pager state should either + ** be OPEN or READER. READER is only possible if the pager is or was in + ** exclusive access mode. */ + assert( sqlite3PcacheRefCount(pPager->pPCache)==0 ); + assert( assert_pager_state(pPager) ); + assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER ); + assert( pPager->errCode==SQLITE_OK ); + + if( !pagerUseWal(pPager) && pPager->eState==PAGER_OPEN ){ + int bHotJournal = 1; /* True if there exists a hot journal-file */ + + assert( !MEMDB ); + assert( pPager->tempFile==0 || pPager->eLock==EXCLUSIVE_LOCK ); + + rc = pager_wait_on_lock(pPager, SHARED_LOCK); + if( rc!=SQLITE_OK ){ + assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK ); + goto failed; + } + + /* If a journal file exists, and there is no RESERVED lock on the + ** database file, then it either needs to be played back or deleted. + */ + if( pPager->eLock<=SHARED_LOCK ){ + rc = hasHotJournal(pPager, &bHotJournal); + } + if( rc!=SQLITE_OK ){ + goto failed; + } + if( bHotJournal ){ + if( pPager->readOnly ){ + rc = SQLITE_READONLY_ROLLBACK; + goto failed; + } + + /* Get an EXCLUSIVE lock on the database file. At this point it is + ** important that a RESERVED lock is not obtained on the way to the + ** EXCLUSIVE lock. If it were, another process might open the + ** database file, detect the RESERVED lock, and conclude that the + ** database is safe to read while this process is still rolling the + ** hot-journal back. + ** + ** Because the intermediate RESERVED lock is not requested, any + ** other process attempting to access the database file will get to + ** this point in the code and fail to obtain its own EXCLUSIVE lock + ** on the database file. + ** + ** Unless the pager is in locking_mode=exclusive mode, the lock is + ** downgraded to SHARED_LOCK before this function returns. + */ + rc = pagerLockDb(pPager, EXCLUSIVE_LOCK); + if( rc!=SQLITE_OK ){ + goto failed; + } + + /* If it is not already open and the file exists on disk, open the + ** journal for read/write access. Write access is required because + ** in exclusive-access mode the file descriptor will be kept open + ** and possibly used for a transaction later on. Also, write-access + ** is usually required to finalize the journal in journal_mode=persist + ** mode (and also for journal_mode=truncate on some systems). + ** + ** If the journal does not exist, it usually means that some + ** other connection managed to get in and roll it back before + ** this connection obtained the exclusive lock above. Or, it + ** may mean that the pager was in the error-state when this + ** function was called and the journal file does not exist. + */ + if( !isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){ + sqlite3_vfs * const pVfs = pPager->pVfs; + int bExists; /* True if journal file exists */ + rc = sqlite3OsAccess( + pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &bExists); + if( rc==SQLITE_OK && bExists ){ + int fout = 0; + int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL; + assert( !pPager->tempFile ); + rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout); + assert( rc!=SQLITE_OK || isOpen(pPager->jfd) ); + if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){ + rc = SQLITE_CANTOPEN_BKPT; + sqlite3OsClose(pPager->jfd); + } + } + } + + /* Playback and delete the journal. Drop the database write + ** lock and reacquire the read lock. Purge the cache before + ** playing back the hot-journal so that we don't end up with + ** an inconsistent cache. Sync the hot journal before playing + ** it back since the process that crashed and left the hot journal + ** probably did not sync it and we are required to always sync + ** the journal before playing it back. + */ + if( isOpen(pPager->jfd) ){ + assert( rc==SQLITE_OK ); + rc = pagerSyncHotJournal(pPager); + if( rc==SQLITE_OK ){ + rc = pager_playback(pPager, !pPager->tempFile); + pPager->eState = PAGER_OPEN; + } + }else if( !pPager->exclusiveMode ){ + pagerUnlockDb(pPager, SHARED_LOCK); + } + + if( rc!=SQLITE_OK ){ + /* This branch is taken if an error occurs while trying to open + ** or roll back a hot-journal while holding an EXCLUSIVE lock. The + ** pager_unlock() routine will be called before returning to unlock + ** the file. If the unlock attempt fails, then Pager.eLock must be + ** set to UNKNOWN_LOCK (see the comment above the #define for + ** UNKNOWN_LOCK above for an explanation). + ** + ** In order to get pager_unlock() to do this, set Pager.eState to + ** PAGER_ERROR now. This is not actually counted as a transition + ** to ERROR state in the state diagram at the top of this file, + ** since we know that the same call to pager_unlock() will very + ** shortly transition the pager object to the OPEN state. Calling + ** assert_pager_state() would fail now, as it should not be possible + ** to be in ERROR state when there are zero outstanding page + ** references. + */ + pager_error(pPager, rc); + goto failed; + } + + assert( pPager->eState==PAGER_OPEN ); + assert( (pPager->eLock==SHARED_LOCK) + || (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK) + ); + } + + if( !pPager->tempFile && pPager->hasHeldSharedLock ){ + /* The shared-lock has just been acquired then check to + ** see if the database has been modified. If the database has changed, + ** flush the cache. The hasHeldSharedLock flag prevents this from + ** occurring on the very first access to a file, in order to save a + ** single unnecessary sqlite3OsRead() call at the start-up. + ** + ** Database changes are detected by looking at 15 bytes beginning + ** at offset 24 into the file. The first 4 of these 16 bytes are + ** a 32-bit counter that is incremented with each change. The + ** other bytes change randomly with each file change when + ** a codec is in use. + ** + ** There is a vanishingly small chance that a change will not be + ** detected. The chance of an undetected change is so small that + ** it can be neglected. + */ + char dbFileVers[sizeof(pPager->dbFileVers)]; + + IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers))); + rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24); + if( rc!=SQLITE_OK ){ + if( rc!=SQLITE_IOERR_SHORT_READ ){ + goto failed; + } + memset(dbFileVers, 0, sizeof(dbFileVers)); + } + + if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){ + pager_reset(pPager); + + /* Unmap the database file. It is possible that external processes + ** may have truncated the database file and then extended it back + ** to its original size while this process was not holding a lock. + ** In this case there may exist a Pager.pMap mapping that appears + ** to be the right size but is not actually valid. Avoid this + ** possibility by unmapping the db here. */ + if( USEFETCH(pPager) ){ + sqlite3OsUnfetch(pPager->fd, 0, 0); + } + } + } + + /* If there is a WAL file in the file-system, open this database in WAL + ** mode. Otherwise, the following function call is a no-op. + */ + rc = pagerOpenWalIfPresent(pPager); +#ifndef SQLITE_OMIT_WAL + assert( pPager->pWal==0 || rc==SQLITE_OK ); +#endif + } + + if( pagerUseWal(pPager) ){ + assert( rc==SQLITE_OK ); + rc = pagerBeginReadTransaction(pPager); + } + + if( pPager->tempFile==0 && pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){ + rc = pagerPagecount(pPager, &pPager->dbSize); + } + + failed: + if( rc!=SQLITE_OK ){ + assert( !MEMDB ); + pager_unlock(pPager); + assert( pPager->eState==PAGER_OPEN ); + }else{ + pPager->eState = PAGER_READER; + pPager->hasHeldSharedLock = 1; + } + return rc; +} + +/* +** If the reference count has reached zero, rollback any active +** transaction and unlock the pager. +** +** Except, in locking_mode=EXCLUSIVE when there is nothing to in +** the rollback journal, the unlock is not performed and there is +** nothing to rollback, so this routine is a no-op. +*/ +static void pagerUnlockIfUnused(Pager *pPager){ + if( sqlite3PcacheRefCount(pPager->pPCache)==0 ){ + assert( pPager->nMmapOut==0 ); /* because page1 is never memory mapped */ + pagerUnlockAndRollback(pPager); + } +} + +/* +** The page getter methods each try to acquire a reference to a +** page with page number pgno. If the requested reference is +** successfully obtained, it is copied to *ppPage and SQLITE_OK returned. +** +** There are different implementations of the getter method depending +** on the current state of the pager. +** +** getPageNormal() -- The normal getter +** getPageError() -- Used if the pager is in an error state +** getPageMmap() -- Used if memory-mapped I/O is enabled +** +** If the requested page is already in the cache, it is returned. +** Otherwise, a new page object is allocated and populated with data +** read from the database file. In some cases, the pcache module may +** choose not to allocate a new page object and may reuse an existing +** object with no outstanding references. +** +** The extra data appended to a page is always initialized to zeros the +** first time a page is loaded into memory. If the page requested is +** already in the cache when this function is called, then the extra +** data is left as it was when the page object was last used. +** +** If the database image is smaller than the requested page or if +** the flags parameter contains the PAGER_GET_NOCONTENT bit and the +** requested page is not already stored in the cache, then no +** actual disk read occurs. In this case the memory image of the +** page is initialized to all zeros. +** +** If PAGER_GET_NOCONTENT is true, it means that we do not care about +** the contents of the page. This occurs in two scenarios: +** +** a) When reading a free-list leaf page from the database, and +** +** b) When a savepoint is being rolled back and we need to load +** a new page into the cache to be filled with the data read +** from the savepoint journal. +** +** If PAGER_GET_NOCONTENT is true, then the data returned is zeroed instead +** of being read from the database. Additionally, the bits corresponding +** to pgno in Pager.pInJournal (bitvec of pages already written to the +** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open +** savepoints are set. This means if the page is made writable at any +** point in the future, using a call to sqlite3PagerWrite(), its contents +** will not be journaled. This saves IO. +** +** The acquisition might fail for several reasons. In all cases, +** an appropriate error code is returned and *ppPage is set to NULL. +** +** See also sqlite3PagerLookup(). Both this routine and Lookup() attempt +** to find a page in the in-memory cache first. If the page is not already +** in memory, this routine goes to disk to read it in whereas Lookup() +** just returns 0. This routine acquires a read-lock the first time it +** has to go to disk, and could also playback an old journal if necessary. +** Since Lookup() never goes to disk, it never has to deal with locks +** or journal files. +*/ +static int getPageNormal( + Pager *pPager, /* The pager open on the database file */ + Pgno pgno, /* Page number to fetch */ + DbPage **ppPage, /* Write a pointer to the page here */ + int flags /* PAGER_GET_XXX flags */ +){ + int rc = SQLITE_OK; + PgHdr *pPg; + u8 noContent; /* True if PAGER_GET_NOCONTENT is set */ + sqlite3_pcache_page *pBase; + + assert( pPager->errCode==SQLITE_OK ); + assert( pPager->eState>=PAGER_READER ); + assert( assert_pager_state(pPager) ); + assert( pPager->hasHeldSharedLock==1 ); + + if( pgno==0 ) return SQLITE_CORRUPT_BKPT; + pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3); + if( pBase==0 ){ + pPg = 0; + rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase); + if( rc!=SQLITE_OK ) goto pager_acquire_err; + if( pBase==0 ){ + rc = SQLITE_NOMEM_BKPT; + goto pager_acquire_err; + } + } + pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase); + assert( pPg==(*ppPage) ); + assert( pPg->pgno==pgno ); + assert( pPg->pPager==pPager || pPg->pPager==0 ); + + noContent = (flags & PAGER_GET_NOCONTENT)!=0; + if( pPg->pPager && !noContent ){ + /* In this case the pcache already contains an initialized copy of + ** the page. Return without further ado. */ + assert( pgno!=PAGER_SJ_PGNO(pPager) ); + pPager->aStat[PAGER_STAT_HIT]++; + return SQLITE_OK; + + }else{ + /* The pager cache has created a new page. Its content needs to + ** be initialized. But first some error checks: + ** + ** (*) obsolete. Was: maximum page number is 2^31 + ** (2) Never try to fetch the locking page + */ + if( pgno==PAGER_SJ_PGNO(pPager) ){ + rc = SQLITE_CORRUPT_BKPT; + goto pager_acquire_err; + } + + pPg->pPager = pPager; + + assert( !isOpen(pPager->fd) || !MEMDB ); + if( !isOpen(pPager->fd) || pPager->dbSize<pgno || noContent ){ + if( pgno>pPager->mxPgno ){ + rc = SQLITE_FULL; + if( pgno<=pPager->dbSize ){ + sqlite3PcacheRelease(pPg); + pPg = 0; + } + goto pager_acquire_err; + } + if( noContent ){ + /* Failure to set the bits in the InJournal bit-vectors is benign. + ** It merely means that we might do some extra work to journal a + ** page that does not need to be journaled. Nevertheless, be sure + ** to test the case where a malloc error occurs while trying to set + ** a bit in a bit vector. + */ + sqlite3BeginBenignMalloc(); + if( pgno<=pPager->dbOrigSize ){ + TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno); + testcase( rc==SQLITE_NOMEM ); + } + TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno); + testcase( rc==SQLITE_NOMEM ); + sqlite3EndBenignMalloc(); + } + memset(pPg->pData, 0, pPager->pageSize); + IOTRACE(("ZERO %p %d\n", pPager, pgno)); + }else{ + assert( pPg->pPager==pPager ); + pPager->aStat[PAGER_STAT_MISS]++; + rc = readDbPage(pPg); + if( rc!=SQLITE_OK ){ + goto pager_acquire_err; + } + } + pager_set_pagehash(pPg); + } + return SQLITE_OK; + +pager_acquire_err: + assert( rc!=SQLITE_OK ); + if( pPg ){ + sqlite3PcacheDrop(pPg); + } + pagerUnlockIfUnused(pPager); + *ppPage = 0; + return rc; +} + +#if SQLITE_MAX_MMAP_SIZE>0 +/* The page getter for when memory-mapped I/O is enabled */ +static int getPageMMap( + Pager *pPager, /* The pager open on the database file */ + Pgno pgno, /* Page number to fetch */ + DbPage **ppPage, /* Write a pointer to the page here */ + int flags /* PAGER_GET_XXX flags */ +){ + int rc = SQLITE_OK; + PgHdr *pPg = 0; + u32 iFrame = 0; /* Frame to read from WAL file */ + + /* It is acceptable to use a read-only (mmap) page for any page except + ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY + ** flag was specified by the caller. And so long as the db is not a + ** temporary or in-memory database. */ + const int bMmapOk = (pgno>1 + && (pPager->eState==PAGER_READER || (flags & PAGER_GET_READONLY)) + ); + + assert( USEFETCH(pPager) ); + + /* Optimization note: Adding the "pgno<=1" term before "pgno==0" here + ** allows the compiler optimizer to reuse the results of the "pgno>1" + ** test in the previous statement, and avoid testing pgno==0 in the + ** common case where pgno is large. */ + if( pgno<=1 && pgno==0 ){ + return SQLITE_CORRUPT_BKPT; + } + assert( pPager->eState>=PAGER_READER ); + assert( assert_pager_state(pPager) ); + assert( pPager->hasHeldSharedLock==1 ); + assert( pPager->errCode==SQLITE_OK ); + + if( bMmapOk && pagerUseWal(pPager) ){ + rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame); + if( rc!=SQLITE_OK ){ + *ppPage = 0; + return rc; + } + } + if( bMmapOk && iFrame==0 ){ + void *pData = 0; + rc = sqlite3OsFetch(pPager->fd, + (i64)(pgno-1) * pPager->pageSize, pPager->pageSize, &pData + ); + if( rc==SQLITE_OK && pData ){ + if( pPager->eState>PAGER_READER || pPager->tempFile ){ + pPg = sqlite3PagerLookup(pPager, pgno); + } + if( pPg==0 ){ + rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg); + }else{ + sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData); + } + if( pPg ){ + assert( rc==SQLITE_OK ); + *ppPage = pPg; + return SQLITE_OK; + } + } + if( rc!=SQLITE_OK ){ + *ppPage = 0; + return rc; + } + } + return getPageNormal(pPager, pgno, ppPage, flags); +} +#endif /* SQLITE_MAX_MMAP_SIZE>0 */ + +/* The page getter method for when the pager is an error state */ +static int getPageError( + Pager *pPager, /* The pager open on the database file */ + Pgno pgno, /* Page number to fetch */ + DbPage **ppPage, /* Write a pointer to the page here */ + int flags /* PAGER_GET_XXX flags */ +){ + UNUSED_PARAMETER(pgno); + UNUSED_PARAMETER(flags); + assert( pPager->errCode!=SQLITE_OK ); + *ppPage = 0; + return pPager->errCode; +} + + +/* Dispatch all page fetch requests to the appropriate getter method. +*/ +int sqlite3PagerGet( + Pager *pPager, /* The pager open on the database file */ + Pgno pgno, /* Page number to fetch */ + DbPage **ppPage, /* Write a pointer to the page here */ + int flags /* PAGER_GET_XXX flags */ +){ +#if 0 /* Trace page fetch by setting to 1 */ + int rc; + printf("PAGE %u\n", pgno); + fflush(stdout); + rc = pPager->xGet(pPager, pgno, ppPage, flags); + if( rc ){ + printf("PAGE %u failed with 0x%02x\n", pgno, rc); + fflush(stdout); + } + return rc; +#else + /* Normal, high-speed version of sqlite3PagerGet() */ + return pPager->xGet(pPager, pgno, ppPage, flags); +#endif +} + +/* +** Acquire a page if it is already in the in-memory cache. Do +** not read the page from disk. Return a pointer to the page, +** or 0 if the page is not in cache. +** +** See also sqlite3PagerGet(). The difference between this routine +** and sqlite3PagerGet() is that _get() will go to the disk and read +** in the page if the page is not already in cache. This routine +** returns NULL if the page is not in cache or if a disk I/O error +** has ever happened. +*/ +DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){ + sqlite3_pcache_page *pPage; + assert( pPager!=0 ); + assert( pgno!=0 ); + assert( pPager->pPCache!=0 ); + pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0); + assert( pPage==0 || pPager->hasHeldSharedLock ); + if( pPage==0 ) return 0; + return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage); +} + +/* +** Release a page reference. +** +** The sqlite3PagerUnref() and sqlite3PagerUnrefNotNull() may only be used +** if we know that the page being released is not the last reference to page1. +** The btree layer always holds page1 open until the end, so these first +** two routines can be used to release any page other than BtShared.pPage1. +** The assert() at tag-20230419-2 proves that this constraint is always +** honored. +** +** Use sqlite3PagerUnrefPageOne() to release page1. This latter routine +** checks the total number of outstanding pages and if the number of +** pages reaches zero it drops the database lock. +*/ +void sqlite3PagerUnrefNotNull(DbPage *pPg){ + TESTONLY( Pager *pPager = pPg->pPager; ) + assert( pPg!=0 ); + if( pPg->flags & PGHDR_MMAP ){ + assert( pPg->pgno!=1 ); /* Page1 is never memory mapped */ + pagerReleaseMapPage(pPg); + }else{ + sqlite3PcacheRelease(pPg); + } + /* Do not use this routine to release the last reference to page1 */ + assert( sqlite3PcacheRefCount(pPager->pPCache)>0 ); /* tag-20230419-2 */ +} +void sqlite3PagerUnref(DbPage *pPg){ + if( pPg ) sqlite3PagerUnrefNotNull(pPg); +} +void sqlite3PagerUnrefPageOne(DbPage *pPg){ + Pager *pPager; + assert( pPg!=0 ); + assert( pPg->pgno==1 ); + assert( (pPg->flags & PGHDR_MMAP)==0 ); /* Page1 is never memory mapped */ + pPager = pPg->pPager; + sqlite3PcacheRelease(pPg); + pagerUnlockIfUnused(pPager); +} + +/* +** This function is called at the start of every write transaction. +** There must already be a RESERVED or EXCLUSIVE lock on the database +** file when this routine is called. +** +** Open the journal file for pager pPager and write a journal header +** to the start of it. If there are active savepoints, open the sub-journal +** as well. This function is only used when the journal file is being +** opened to write a rollback log for a transaction. It is not used +** when opening a hot journal file to roll it back. +** +** If the journal file is already open (as it may be in exclusive mode), +** then this function just writes a journal header to the start of the +** already open file. +** +** Whether or not the journal file is opened by this function, the +** Pager.pInJournal bitvec structure is allocated. +** +** Return SQLITE_OK if everything is successful. Otherwise, return +** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or +** an IO error code if opening or writing the journal file fails. +*/ +static int pager_open_journal(Pager *pPager){ + int rc = SQLITE_OK; /* Return code */ + sqlite3_vfs * const pVfs = pPager->pVfs; /* Local cache of vfs pointer */ + + assert( pPager->eState==PAGER_WRITER_LOCKED ); + assert( assert_pager_state(pPager) ); + assert( pPager->pInJournal==0 ); + + /* If already in the error state, this function is a no-op. But on + ** the other hand, this routine is never called if we are already in + ** an error state. */ + if( NEVER(pPager->errCode) ) return pPager->errCode; + + if( !pagerUseWal(pPager) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){ + pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize); + if( pPager->pInJournal==0 ){ + return SQLITE_NOMEM_BKPT; + } + + /* Open the journal file if it is not already open. */ + if( !isOpen(pPager->jfd) ){ + if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){ + sqlite3MemJournalOpen(pPager->jfd); + }else{ + int flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE; + int nSpill; + + if( pPager->tempFile ){ + flags |= (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL); + flags |= SQLITE_OPEN_EXCLUSIVE; + nSpill = sqlite3Config.nStmtSpill; + }else{ + flags |= SQLITE_OPEN_MAIN_JOURNAL; + nSpill = jrnlBufferSize(pPager); + } + + /* Verify that the database still has the same name as it did when + ** it was originally opened. */ + rc = databaseIsUnmoved(pPager); + if( rc==SQLITE_OK ){ + rc = sqlite3JournalOpen ( + pVfs, pPager->zJournal, pPager->jfd, flags, nSpill + ); + } + } + assert( rc!=SQLITE_OK || isOpen(pPager->jfd) ); + } + + + /* Write the first journal header to the journal file and open + ** the sub-journal if necessary. + */ + if( rc==SQLITE_OK ){ + /* TODO: Check if all of these are really required. */ + pPager->nRec = 0; + pPager->journalOff = 0; + pPager->setSuper = 0; + pPager->journalHdr = 0; + rc = writeJournalHdr(pPager); + } + } + + if( rc!=SQLITE_OK ){ + sqlite3BitvecDestroy(pPager->pInJournal); + pPager->pInJournal = 0; + pPager->journalOff = 0; + }else{ + assert( pPager->eState==PAGER_WRITER_LOCKED ); + pPager->eState = PAGER_WRITER_CACHEMOD; + } + + return rc; +} + +/* +** Begin a write-transaction on the specified pager object. If a +** write-transaction has already been opened, this function is a no-op. +** +** If the exFlag argument is false, then acquire at least a RESERVED +** lock on the database file. If exFlag is true, then acquire at least +** an EXCLUSIVE lock. If such a lock is already held, no locking +** functions need be called. +** +** If the subjInMemory argument is non-zero, then any sub-journal opened +** within this transaction will be opened as an in-memory file. This +** has no effect if the sub-journal is already opened (as it may be when +** running in exclusive mode) or if the transaction does not require a +** sub-journal. If the subjInMemory argument is zero, then any required +** sub-journal is implemented in-memory if pPager is an in-memory database, +** or using a temporary file otherwise. +*/ +int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){ + int rc = SQLITE_OK; + + if( pPager->errCode ) return pPager->errCode; + assert( pPager->eState>=PAGER_READER && pPager->eState<PAGER_ERROR ); + pPager->subjInMemory = (u8)subjInMemory; + + if( pPager->eState==PAGER_READER ){ + assert( pPager->pInJournal==0 ); + + if( pagerUseWal(pPager) ){ + /* If the pager is configured to use locking_mode=exclusive, and an + ** exclusive lock on the database is not already held, obtain it now. + */ + if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){ + rc = pagerLockDb(pPager, EXCLUSIVE_LOCK); + if( rc!=SQLITE_OK ){ + return rc; + } + (void)sqlite3WalExclusiveMode(pPager->pWal, 1); + } + + /* Grab the write lock on the log file. If successful, upgrade to + ** PAGER_RESERVED state. Otherwise, return an error code to the caller. + ** The busy-handler is not invoked if another connection already + ** holds the write-lock. If possible, the upper layer will call it. + */ + rc = sqlite3WalBeginWriteTransaction(pPager->pWal); + }else{ + /* Obtain a RESERVED lock on the database file. If the exFlag parameter + ** is true, then immediately upgrade this to an EXCLUSIVE lock. The + ** busy-handler callback can be used when upgrading to the EXCLUSIVE + ** lock, but not when obtaining the RESERVED lock. + */ + rc = pagerLockDb(pPager, RESERVED_LOCK); + if( rc==SQLITE_OK && exFlag ){ + rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK); + } + } + + if( rc==SQLITE_OK ){ + /* Change to WRITER_LOCKED state. + ** + ** WAL mode sets Pager.eState to PAGER_WRITER_LOCKED or CACHEMOD + ** when it has an open transaction, but never to DBMOD or FINISHED. + ** This is because in those states the code to roll back savepoint + ** transactions may copy data from the sub-journal into the database + ** file as well as into the page cache. Which would be incorrect in + ** WAL mode. + */ + pPager->eState = PAGER_WRITER_LOCKED; + pPager->dbHintSize = pPager->dbSize; + pPager->dbFileSize = pPager->dbSize; + pPager->dbOrigSize = pPager->dbSize; + pPager->journalOff = 0; + } + + assert( rc==SQLITE_OK || pPager->eState==PAGER_READER ); + assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED ); + assert( assert_pager_state(pPager) ); + } + + PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager))); + return rc; +} + +/* +** Write page pPg onto the end of the rollback journal. +*/ +static SQLITE_NOINLINE int pagerAddPageToRollbackJournal(PgHdr *pPg){ + Pager *pPager = pPg->pPager; + int rc; + u32 cksum; + char *pData2; + i64 iOff = pPager->journalOff; + + /* We should never write to the journal file the page that + ** contains the database locks. The following assert verifies + ** that we do not. */ + assert( pPg->pgno!=PAGER_SJ_PGNO(pPager) ); + + assert( pPager->journalHdr<=pPager->journalOff ); + pData2 = pPg->pData; + cksum = pager_cksum(pPager, (u8*)pData2); + + /* Even if an IO or diskfull error occurs while journalling the + ** page in the block above, set the need-sync flag for the page. + ** Otherwise, when the transaction is rolled back, the logic in + ** playback_one_page() will think that the page needs to be restored + ** in the database file. And if an IO error occurs while doing so, + ** then corruption may follow. + */ + pPg->flags |= PGHDR_NEED_SYNC; + + rc = write32bits(pPager->jfd, iOff, pPg->pgno); + if( rc!=SQLITE_OK ) return rc; + rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4); + if( rc!=SQLITE_OK ) return rc; + rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum); + if( rc!=SQLITE_OK ) return rc; + + IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, + pPager->journalOff, pPager->pageSize)); + PAGER_INCR(sqlite3_pager_writej_count); + PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n", + PAGERID(pPager), pPg->pgno, + ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg))); + + pPager->journalOff += 8 + pPager->pageSize; + pPager->nRec++; + assert( pPager->pInJournal!=0 ); + rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno); + testcase( rc==SQLITE_NOMEM ); + assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); + rc |= addToSavepointBitvecs(pPager, pPg->pgno); + assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); + return rc; +} + +/* +** Mark a single data page as writeable. The page is written into the +** main journal or sub-journal as required. If the page is written into +** one of the journals, the corresponding bit is set in the +** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs +** of any open savepoints as appropriate. +*/ +static int pager_write(PgHdr *pPg){ + Pager *pPager = pPg->pPager; + int rc = SQLITE_OK; + + /* This routine is not called unless a write-transaction has already + ** been started. The journal file may or may not be open at this point. + ** It is never called in the ERROR state. + */ + assert( pPager->eState==PAGER_WRITER_LOCKED + || pPager->eState==PAGER_WRITER_CACHEMOD + || pPager->eState==PAGER_WRITER_DBMOD + ); + assert( assert_pager_state(pPager) ); + assert( pPager->errCode==0 ); + assert( pPager->readOnly==0 ); + CHECK_PAGE(pPg); + + /* The journal file needs to be opened. Higher level routines have already + ** obtained the necessary locks to begin the write-transaction, but the + ** rollback journal might not yet be open. Open it now if this is the case. + ** + ** This is done before calling sqlite3PcacheMakeDirty() on the page. + ** Otherwise, if it were done after calling sqlite3PcacheMakeDirty(), then + ** an error might occur and the pager would end up in WRITER_LOCKED state + ** with pages marked as dirty in the cache. + */ + if( pPager->eState==PAGER_WRITER_LOCKED ){ + rc = pager_open_journal(pPager); + if( rc!=SQLITE_OK ) return rc; + } + assert( pPager->eState>=PAGER_WRITER_CACHEMOD ); + assert( assert_pager_state(pPager) ); + + /* Mark the page that is about to be modified as dirty. */ + sqlite3PcacheMakeDirty(pPg); + + /* If a rollback journal is in use, them make sure the page that is about + ** to change is in the rollback journal, or if the page is a new page off + ** then end of the file, make sure it is marked as PGHDR_NEED_SYNC. + */ + assert( (pPager->pInJournal!=0) == isOpen(pPager->jfd) ); + if( pPager->pInJournal!=0 + && sqlite3BitvecTestNotNull(pPager->pInJournal, pPg->pgno)==0 + ){ + assert( pagerUseWal(pPager)==0 ); + if( pPg->pgno<=pPager->dbOrigSize ){ + rc = pagerAddPageToRollbackJournal(pPg); + if( rc!=SQLITE_OK ){ + return rc; + } + }else{ + if( pPager->eState!=PAGER_WRITER_DBMOD ){ + pPg->flags |= PGHDR_NEED_SYNC; + } + PAGERTRACE(("APPEND %d page %d needSync=%d\n", + PAGERID(pPager), pPg->pgno, + ((pPg->flags&PGHDR_NEED_SYNC)?1:0))); + } + } + + /* The PGHDR_DIRTY bit is set above when the page was added to the dirty-list + ** and before writing the page into the rollback journal. Wait until now, + ** after the page has been successfully journalled, before setting the + ** PGHDR_WRITEABLE bit that indicates that the page can be safely modified. + */ + pPg->flags |= PGHDR_WRITEABLE; + + /* If the statement journal is open and the page is not in it, + ** then write the page into the statement journal. + */ + if( pPager->nSavepoint>0 ){ + rc = subjournalPageIfRequired(pPg); + } + + /* Update the database size and return. */ + if( pPager->dbSize<pPg->pgno ){ + pPager->dbSize = pPg->pgno; + } + return rc; +} + +/* +** This is a variant of sqlite3PagerWrite() that runs when the sector size +** is larger than the page size. SQLite makes the (reasonable) assumption that +** all bytes of a sector are written together by hardware. Hence, all bytes of +** a sector need to be journalled in case of a power loss in the middle of +** a write. +** +** Usually, the sector size is less than or equal to the page size, in which +** case pages can be individually written. This routine only runs in the +** exceptional case where the page size is smaller than the sector size. +*/ +static SQLITE_NOINLINE int pagerWriteLargeSector(PgHdr *pPg){ + int rc = SQLITE_OK; /* Return code */ + Pgno nPageCount; /* Total number of pages in database file */ + Pgno pg1; /* First page of the sector pPg is located on. */ + int nPage = 0; /* Number of pages starting at pg1 to journal */ + int ii; /* Loop counter */ + int needSync = 0; /* True if any page has PGHDR_NEED_SYNC */ + Pager *pPager = pPg->pPager; /* The pager that owns pPg */ + Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize); + + /* Set the doNotSpill NOSYNC bit to 1. This is because we cannot allow + ** a journal header to be written between the pages journaled by + ** this function. + */ + assert( !MEMDB ); + assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)==0 ); + pPager->doNotSpill |= SPILLFLAG_NOSYNC; + + /* This trick assumes that both the page-size and sector-size are + ** an integer power of 2. It sets variable pg1 to the identifier + ** of the first page of the sector pPg is located on. + */ + pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1; + + nPageCount = pPager->dbSize; + if( pPg->pgno>nPageCount ){ + nPage = (pPg->pgno - pg1)+1; + }else if( (pg1+nPagePerSector-1)>nPageCount ){ + nPage = nPageCount+1-pg1; + }else{ + nPage = nPagePerSector; + } + assert(nPage>0); + assert(pg1<=pPg->pgno); + assert((pg1+nPage)>pPg->pgno); + + for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){ + Pgno pg = pg1+ii; + PgHdr *pPage; + if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){ + if( pg!=PAGER_SJ_PGNO(pPager) ){ + rc = sqlite3PagerGet(pPager, pg, &pPage, 0); + if( rc==SQLITE_OK ){ + rc = pager_write(pPage); + if( pPage->flags&PGHDR_NEED_SYNC ){ + needSync = 1; + } + sqlite3PagerUnrefNotNull(pPage); + } + } + }else if( (pPage = sqlite3PagerLookup(pPager, pg))!=0 ){ + if( pPage->flags&PGHDR_NEED_SYNC ){ + needSync = 1; + } + sqlite3PagerUnrefNotNull(pPage); + } + } + + /* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages + ** starting at pg1, then it needs to be set for all of them. Because + ** writing to any of these nPage pages may damage the others, the + ** journal file must contain sync()ed copies of all of them + ** before any of them can be written out to the database file. + */ + if( rc==SQLITE_OK && needSync ){ + assert( !MEMDB ); + for(ii=0; ii<nPage; ii++){ + PgHdr *pPage = sqlite3PagerLookup(pPager, pg1+ii); + if( pPage ){ + pPage->flags |= PGHDR_NEED_SYNC; + sqlite3PagerUnrefNotNull(pPage); + } + } + } + + assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)!=0 ); + pPager->doNotSpill &= ~SPILLFLAG_NOSYNC; + return rc; +} + +/* +** Mark a data page as writeable. This routine must be called before +** making changes to a page. The caller must check the return value +** of this function and be careful not to change any page data unless +** this routine returns SQLITE_OK. +** +** The difference between this function and pager_write() is that this +** function also deals with the special case where 2 or more pages +** fit on a single disk sector. In this case all co-resident pages +** must have been written to the journal file before returning. +** +** If an error occurs, SQLITE_NOMEM or an IO error code is returned +** as appropriate. Otherwise, SQLITE_OK. +*/ +int sqlite3PagerWrite(PgHdr *pPg){ + Pager *pPager = pPg->pPager; + assert( (pPg->flags & PGHDR_MMAP)==0 ); + assert( pPager->eState>=PAGER_WRITER_LOCKED ); + assert( assert_pager_state(pPager) ); + if( (pPg->flags & PGHDR_WRITEABLE)!=0 && pPager->dbSize>=pPg->pgno ){ + if( pPager->nSavepoint ) return subjournalPageIfRequired(pPg); + return SQLITE_OK; + }else if( pPager->errCode ){ + return pPager->errCode; + }else if( pPager->sectorSize > (u32)pPager->pageSize ){ + assert( pPager->tempFile==0 ); + return pagerWriteLargeSector(pPg); + }else{ + return pager_write(pPg); + } +} + +/* +** Return TRUE if the page given in the argument was previously passed +** to sqlite3PagerWrite(). In other words, return TRUE if it is ok +** to change the content of the page. +*/ +#ifndef NDEBUG +int sqlite3PagerIswriteable(DbPage *pPg){ + return pPg->flags & PGHDR_WRITEABLE; +} +#endif + +/* +** A call to this routine tells the pager that it is not necessary to +** write the information on page pPg back to the disk, even though +** that page might be marked as dirty. This happens, for example, when +** the page has been added as a leaf of the freelist and so its +** content no longer matters. +** +** The overlying software layer calls this routine when all of the data +** on the given page is unused. The pager marks the page as clean so +** that it does not get written to disk. +** +** Tests show that this optimization can quadruple the speed of large +** DELETE operations. +** +** This optimization cannot be used with a temp-file, as the page may +** have been dirty at the start of the transaction. In that case, if +** memory pressure forces page pPg out of the cache, the data does need +** to be written out to disk so that it may be read back in if the +** current transaction is rolled back. +*/ +void sqlite3PagerDontWrite(PgHdr *pPg){ + Pager *pPager = pPg->pPager; + if( !pPager->tempFile && (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){ + PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager))); + IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno)) + pPg->flags |= PGHDR_DONT_WRITE; + pPg->flags &= ~PGHDR_WRITEABLE; + testcase( pPg->flags & PGHDR_NEED_SYNC ); + pager_set_pagehash(pPg); + } +} + +/* +** This routine is called to increment the value of the database file +** change-counter, stored as a 4-byte big-endian integer starting at +** byte offset 24 of the pager file. The secondary change counter at +** 92 is also updated, as is the SQLite version number at offset 96. +** +** But this only happens if the pPager->changeCountDone flag is false. +** To avoid excess churning of page 1, the update only happens once. +** See also the pager_write_changecounter() routine that does an +** unconditional update of the change counters. +** +** If the isDirectMode flag is zero, then this is done by calling +** sqlite3PagerWrite() on page 1, then modifying the contents of the +** page data. In this case the file will be updated when the current +** transaction is committed. +** +** The isDirectMode flag may only be non-zero if the library was compiled +** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case, +** if isDirect is non-zero, then the database file is updated directly +** by writing an updated version of page 1 using a call to the +** sqlite3OsWrite() function. +*/ +static int pager_incr_changecounter(Pager *pPager, int isDirectMode){ + int rc = SQLITE_OK; + + assert( pPager->eState==PAGER_WRITER_CACHEMOD + || pPager->eState==PAGER_WRITER_DBMOD + ); + assert( assert_pager_state(pPager) ); + + /* Declare and initialize constant integer 'isDirect'. If the + ** atomic-write optimization is enabled in this build, then isDirect + ** is initialized to the value passed as the isDirectMode parameter + ** to this function. Otherwise, it is always set to zero. + ** + ** The idea is that if the atomic-write optimization is not + ** enabled at compile time, the compiler can omit the tests of + ** 'isDirect' below, as well as the block enclosed in the + ** "if( isDirect )" condition. + */ +#ifndef SQLITE_ENABLE_ATOMIC_WRITE +# define DIRECT_MODE 0 + assert( isDirectMode==0 ); + UNUSED_PARAMETER(isDirectMode); +#else +# define DIRECT_MODE isDirectMode +#endif + + if( !pPager->changeCountDone && pPager->dbSize>0 ){ + PgHdr *pPgHdr; /* Reference to page 1 */ + + assert( !pPager->tempFile && isOpen(pPager->fd) ); + + /* Open page 1 of the file for writing. */ + rc = sqlite3PagerGet(pPager, 1, &pPgHdr, 0); + assert( pPgHdr==0 || rc==SQLITE_OK ); + + /* If page one was fetched successfully, and this function is not + ** operating in direct-mode, make page 1 writable. When not in + ** direct mode, page 1 is always held in cache and hence the PagerGet() + ** above is always successful - hence the ALWAYS on rc==SQLITE_OK. + */ + if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){ + rc = sqlite3PagerWrite(pPgHdr); + } + + if( rc==SQLITE_OK ){ + /* Actually do the update of the change counter */ + pager_write_changecounter(pPgHdr); + + /* If running in direct mode, write the contents of page 1 to the file. */ + if( DIRECT_MODE ){ + const void *zBuf; + assert( pPager->dbFileSize>0 ); + zBuf = pPgHdr->pData; + if( rc==SQLITE_OK ){ + rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0); + pPager->aStat[PAGER_STAT_WRITE]++; + } + if( rc==SQLITE_OK ){ + /* Update the pager's copy of the change-counter. Otherwise, the + ** next time a read transaction is opened the cache will be + ** flushed (as the change-counter values will not match). */ + const void *pCopy = (const void *)&((const char *)zBuf)[24]; + memcpy(&pPager->dbFileVers, pCopy, sizeof(pPager->dbFileVers)); + pPager->changeCountDone = 1; + } + }else{ + pPager->changeCountDone = 1; + } + } + + /* Release the page reference. */ + sqlite3PagerUnref(pPgHdr); + } + return rc; +} + +/* +** Sync the database file to disk. This is a no-op for in-memory databases +** or pages with the Pager.noSync flag set. +** +** If successful, or if called on a pager for which it is a no-op, this +** function returns SQLITE_OK. Otherwise, an IO error code is returned. +*/ +int sqlite3PagerSync(Pager *pPager, const char *zSuper){ + int rc = SQLITE_OK; + void *pArg = (void*)zSuper; + rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, pArg); + if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK; + if( rc==SQLITE_OK && !pPager->noSync ){ + assert( !MEMDB ); + rc = sqlite3OsSync(pPager->fd, pPager->syncFlags); + } + return rc; +} + +/* +** This function may only be called while a write-transaction is active in +** rollback. If the connection is in WAL mode, this call is a no-op. +** Otherwise, if the connection does not already have an EXCLUSIVE lock on +** the database file, an attempt is made to obtain one. +** +** If the EXCLUSIVE lock is already held or the attempt to obtain it is +** successful, or the connection is in WAL mode, SQLITE_OK is returned. +** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is +** returned. +*/ +int sqlite3PagerExclusiveLock(Pager *pPager){ + int rc = pPager->errCode; + assert( assert_pager_state(pPager) ); + if( rc==SQLITE_OK ){ + assert( pPager->eState==PAGER_WRITER_CACHEMOD + || pPager->eState==PAGER_WRITER_DBMOD + || pPager->eState==PAGER_WRITER_LOCKED + ); + assert( assert_pager_state(pPager) ); + if( 0==pagerUseWal(pPager) ){ + rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK); + } + } + return rc; +} + +/* +** Sync the database file for the pager pPager. zSuper points to the name +** of a super-journal file that should be written into the individual +** journal file. zSuper may be NULL, which is interpreted as no +** super-journal (a single database transaction). +** +** This routine ensures that: +** +** * The database file change-counter is updated, +** * the journal is synced (unless the atomic-write optimization is used), +** * all dirty pages are written to the database file, +** * the database file is truncated (if required), and +** * the database file synced. +** +** The only thing that remains to commit the transaction is to finalize +** (delete, truncate or zero the first part of) the journal file (or +** delete the super-journal file if specified). +** +** Note that if zSuper==NULL, this does not overwrite a previous value +** passed to an sqlite3PagerCommitPhaseOne() call. +** +** If the final parameter - noSync - is true, then the database file itself +** is not synced. The caller must call sqlite3PagerSync() directly to +** sync the database file before calling CommitPhaseTwo() to delete the +** journal file in this case. +*/ +int sqlite3PagerCommitPhaseOne( + Pager *pPager, /* Pager object */ + const char *zSuper, /* If not NULL, the super-journal name */ + int noSync /* True to omit the xSync on the db file */ +){ + int rc = SQLITE_OK; /* Return code */ + + assert( pPager->eState==PAGER_WRITER_LOCKED + || pPager->eState==PAGER_WRITER_CACHEMOD + || pPager->eState==PAGER_WRITER_DBMOD + || pPager->eState==PAGER_ERROR + ); + assert( assert_pager_state(pPager) ); + + /* If a prior error occurred, report that error again. */ + if( NEVER(pPager->errCode) ) return pPager->errCode; + + /* Provide the ability to easily simulate an I/O error during testing */ + if( sqlite3FaultSim(400) ) return SQLITE_IOERR; + + PAGERTRACE(("DATABASE SYNC: File=%s zSuper=%s nSize=%d\n", + pPager->zFilename, zSuper, pPager->dbSize)); + + /* If no database changes have been made, return early. */ + if( pPager->eState<PAGER_WRITER_CACHEMOD ) return SQLITE_OK; + + assert( MEMDB==0 || pPager->tempFile ); + assert( isOpen(pPager->fd) || pPager->tempFile ); + if( 0==pagerFlushOnCommit(pPager, 1) ){ + /* If this is an in-memory db, or no pages have been written to, or this + ** function has already been called, it is mostly a no-op. However, any + ** backup in progress needs to be restarted. */ + sqlite3BackupRestart(pPager->pBackup); + }else{ + PgHdr *pList; + if( pagerUseWal(pPager) ){ + PgHdr *pPageOne = 0; + pList = sqlite3PcacheDirtyList(pPager->pPCache); + if( pList==0 ){ + /* Must have at least one page for the WAL commit flag. + ** Ticket [2d1a5c67dfc2363e44f29d9bbd57f] 2011-05-18 */ + rc = sqlite3PagerGet(pPager, 1, &pPageOne, 0); + pList = pPageOne; + pList->pDirty = 0; + } + assert( rc==SQLITE_OK ); + if( ALWAYS(pList) ){ + rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1); + } + sqlite3PagerUnref(pPageOne); + if( rc==SQLITE_OK ){ + sqlite3PcacheCleanAll(pPager->pPCache); + } + }else{ + /* The bBatch boolean is true if the batch-atomic-write commit method + ** should be used. No rollback journal is created if batch-atomic-write + ** is enabled. + */ +#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE + sqlite3_file *fd = pPager->fd; + int bBatch = zSuper==0 /* An SQLITE_IOCAP_BATCH_ATOMIC commit */ + && (sqlite3OsDeviceCharacteristics(fd) & SQLITE_IOCAP_BATCH_ATOMIC) + && !pPager->noSync + && sqlite3JournalIsInMemory(pPager->jfd); +#else +# define bBatch 0 +#endif + +#ifdef SQLITE_ENABLE_ATOMIC_WRITE + /* The following block updates the change-counter. Exactly how it + ** does this depends on whether or not the atomic-update optimization + ** was enabled at compile time, and if this transaction meets the + ** runtime criteria to use the operation: + ** + ** * The file-system supports the atomic-write property for + ** blocks of size page-size, and + ** * This commit is not part of a multi-file transaction, and + ** * Exactly one page has been modified and store in the journal file. + ** + ** If the optimization was not enabled at compile time, then the + ** pager_incr_changecounter() function is called to update the change + ** counter in 'indirect-mode'. If the optimization is compiled in but + ** is not applicable to this transaction, call sqlite3JournalCreate() + ** to make sure the journal file has actually been created, then call + ** pager_incr_changecounter() to update the change-counter in indirect + ** mode. + ** + ** Otherwise, if the optimization is both enabled and applicable, + ** then call pager_incr_changecounter() to update the change-counter + ** in 'direct' mode. In this case the journal file will never be + ** created for this transaction. + */ + if( bBatch==0 ){ + PgHdr *pPg; + assert( isOpen(pPager->jfd) + || pPager->journalMode==PAGER_JOURNALMODE_OFF + || pPager->journalMode==PAGER_JOURNALMODE_WAL + ); + if( !zSuper && isOpen(pPager->jfd) + && pPager->journalOff==jrnlBufferSize(pPager) + && pPager->dbSize>=pPager->dbOrigSize + && (!(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty) + ){ + /* Update the db file change counter via the direct-write method. The + ** following call will modify the in-memory representation of page 1 + ** to include the updated change counter and then write page 1 + ** directly to the database file. Because of the atomic-write + ** property of the host file-system, this is safe. + */ + rc = pager_incr_changecounter(pPager, 1); + }else{ + rc = sqlite3JournalCreate(pPager->jfd); + if( rc==SQLITE_OK ){ + rc = pager_incr_changecounter(pPager, 0); + } + } + } +#else /* SQLITE_ENABLE_ATOMIC_WRITE */ +#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE + if( zSuper ){ + rc = sqlite3JournalCreate(pPager->jfd); + if( rc!=SQLITE_OK ) goto commit_phase_one_exit; + assert( bBatch==0 ); + } +#endif + rc = pager_incr_changecounter(pPager, 0); +#endif /* !SQLITE_ENABLE_ATOMIC_WRITE */ + if( rc!=SQLITE_OK ) goto commit_phase_one_exit; + + /* Write the super-journal name into the journal file. If a + ** super-journal file name has already been written to the journal file, + ** or if zSuper is NULL (no super-journal), then this call is a no-op. + */ + rc = writeSuperJournal(pPager, zSuper); + if( rc!=SQLITE_OK ) goto commit_phase_one_exit; + + /* Sync the journal file and write all dirty pages to the database. + ** If the atomic-update optimization is being used, this sync will not + ** create the journal file or perform any real IO. + ** + ** Because the change-counter page was just modified, unless the + ** atomic-update optimization is used it is almost certain that the + ** journal requires a sync here. However, in locking_mode=exclusive + ** on a system under memory pressure it is just possible that this is + ** not the case. In this case it is likely enough that the redundant + ** xSync() call will be changed to a no-op by the OS anyhow. + */ + rc = syncJournal(pPager, 0); + if( rc!=SQLITE_OK ) goto commit_phase_one_exit; + + pList = sqlite3PcacheDirtyList(pPager->pPCache); +#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE + if( bBatch ){ + rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_BEGIN_ATOMIC_WRITE, 0); + if( rc==SQLITE_OK ){ + rc = pager_write_pagelist(pPager, pList); + if( rc==SQLITE_OK && pPager->dbSize>pPager->dbFileSize ){ + char *pTmp = pPager->pTmpSpace; + int szPage = (int)pPager->pageSize; + memset(pTmp, 0, szPage); + rc = sqlite3OsWrite(pPager->fd, pTmp, szPage, + ((i64)pPager->dbSize*pPager->pageSize)-szPage); + } + if( rc==SQLITE_OK ){ + rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_COMMIT_ATOMIC_WRITE, 0); + } + if( rc!=SQLITE_OK ){ + sqlite3OsFileControlHint(fd, SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE, 0); + } + } + + if( (rc&0xFF)==SQLITE_IOERR && rc!=SQLITE_IOERR_NOMEM ){ + rc = sqlite3JournalCreate(pPager->jfd); + if( rc!=SQLITE_OK ){ + sqlite3OsClose(pPager->jfd); + goto commit_phase_one_exit; + } + bBatch = 0; + }else{ + sqlite3OsClose(pPager->jfd); + } + } +#endif /* SQLITE_ENABLE_BATCH_ATOMIC_WRITE */ + + if( bBatch==0 ){ + rc = pager_write_pagelist(pPager, pList); + } + if( rc!=SQLITE_OK ){ + assert( rc!=SQLITE_IOERR_BLOCKED ); + goto commit_phase_one_exit; + } + sqlite3PcacheCleanAll(pPager->pPCache); + + /* If the file on disk is smaller than the database image, use + ** pager_truncate to grow the file here. This can happen if the database + ** image was extended as part of the current transaction and then the + ** last page in the db image moved to the free-list. In this case the + ** last page is never written out to disk, leaving the database file + ** undersized. Fix this now if it is the case. */ + if( pPager->dbSize>pPager->dbFileSize ){ + Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_SJ_PGNO(pPager)); + assert( pPager->eState==PAGER_WRITER_DBMOD ); + rc = pager_truncate(pPager, nNew); + if( rc!=SQLITE_OK ) goto commit_phase_one_exit; + } + + /* Finally, sync the database file. */ + if( !noSync ){ + rc = sqlite3PagerSync(pPager, zSuper); + } + IOTRACE(("DBSYNC %p\n", pPager)) + } + } + +commit_phase_one_exit: + if( rc==SQLITE_OK && !pagerUseWal(pPager) ){ + pPager->eState = PAGER_WRITER_FINISHED; + } + return rc; +} + + +/* +** When this function is called, the database file has been completely +** updated to reflect the changes made by the current transaction and +** synced to disk. The journal file still exists in the file-system +** though, and if a failure occurs at this point it will eventually +** be used as a hot-journal and the current transaction rolled back. +** +** This function finalizes the journal file, either by deleting, +** truncating or partially zeroing it, so that it cannot be used +** for hot-journal rollback. Once this is done the transaction is +** irrevocably committed. +** +** If an error occurs, an IO error code is returned and the pager +** moves into the error state. Otherwise, SQLITE_OK is returned. +*/ +int sqlite3PagerCommitPhaseTwo(Pager *pPager){ + int rc = SQLITE_OK; /* Return code */ + + /* This routine should not be called if a prior error has occurred. + ** But if (due to a coding error elsewhere in the system) it does get + ** called, just return the same error code without doing anything. */ + if( NEVER(pPager->errCode) ) return pPager->errCode; + pPager->iDataVersion++; + + assert( pPager->eState==PAGER_WRITER_LOCKED + || pPager->eState==PAGER_WRITER_FINISHED + || (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD) + ); + assert( assert_pager_state(pPager) ); + + /* An optimization. If the database was not actually modified during + ** this transaction, the pager is running in exclusive-mode and is + ** using persistent journals, then this function is a no-op. + ** + ** The start of the journal file currently contains a single journal + ** header with the nRec field set to 0. If such a journal is used as + ** a hot-journal during hot-journal rollback, 0 changes will be made + ** to the database file. So there is no need to zero the journal + ** header. Since the pager is in exclusive mode, there is no need + ** to drop any locks either. + */ + if( pPager->eState==PAGER_WRITER_LOCKED + && pPager->exclusiveMode + && pPager->journalMode==PAGER_JOURNALMODE_PERSIST + ){ + assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff ); + pPager->eState = PAGER_READER; + return SQLITE_OK; + } + + PAGERTRACE(("COMMIT %d\n", PAGERID(pPager))); + rc = pager_end_transaction(pPager, pPager->setSuper, 1); + return pager_error(pPager, rc); +} + +/* +** If a write transaction is open, then all changes made within the +** transaction are reverted and the current write-transaction is closed. +** The pager falls back to PAGER_READER state if successful, or PAGER_ERROR +** state if an error occurs. +** +** If the pager is already in PAGER_ERROR state when this function is called, +** it returns Pager.errCode immediately. No work is performed in this case. +** +** Otherwise, in rollback mode, this function performs two functions: +** +** 1) It rolls back the journal file, restoring all database file and +** in-memory cache pages to the state they were in when the transaction +** was opened, and +** +** 2) It finalizes the journal file, so that it is not used for hot +** rollback at any point in the future. +** +** Finalization of the journal file (task 2) is only performed if the +** rollback is successful. +** +** In WAL mode, all cache-entries containing data modified within the +** current transaction are either expelled from the cache or reverted to +** their pre-transaction state by re-reading data from the database or +** WAL files. The WAL transaction is then closed. +*/ +int sqlite3PagerRollback(Pager *pPager){ + int rc = SQLITE_OK; /* Return code */ + PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager))); + + /* PagerRollback() is a no-op if called in READER or OPEN state. If + ** the pager is already in the ERROR state, the rollback is not + ** attempted here. Instead, the error code is returned to the caller. + */ + assert( assert_pager_state(pPager) ); + if( pPager->eState==PAGER_ERROR ) return pPager->errCode; + if( pPager->eState<=PAGER_READER ) return SQLITE_OK; + + if( pagerUseWal(pPager) ){ + int rc2; + rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1); + rc2 = pager_end_transaction(pPager, pPager->setSuper, 0); + if( rc==SQLITE_OK ) rc = rc2; + }else if( !isOpen(pPager->jfd) || pPager->eState==PAGER_WRITER_LOCKED ){ + int eState = pPager->eState; + rc = pager_end_transaction(pPager, 0, 0); + if( !MEMDB && eState>PAGER_WRITER_LOCKED ){ + /* This can happen using journal_mode=off. Move the pager to the error + ** state to indicate that the contents of the cache may not be trusted. + ** Any active readers will get SQLITE_ABORT. + */ + pPager->errCode = SQLITE_ABORT; + pPager->eState = PAGER_ERROR; + setGetterMethod(pPager); + return rc; + } + }else{ + rc = pager_playback(pPager, 0); + } + + assert( pPager->eState==PAGER_READER || rc!=SQLITE_OK ); + assert( rc==SQLITE_OK || rc==SQLITE_FULL || rc==SQLITE_CORRUPT + || rc==SQLITE_NOMEM || (rc&0xFF)==SQLITE_IOERR + || rc==SQLITE_CANTOPEN + ); + + /* If an error occurs during a ROLLBACK, we can no longer trust the pager + ** cache. So call pager_error() on the way out to make any error persistent. + */ + return pager_error(pPager, rc); +} + +/* +** Return TRUE if the database file is opened read-only. Return FALSE +** if the database is (in theory) writable. +*/ +u8 sqlite3PagerIsreadonly(Pager *pPager){ + return pPager->readOnly; +} + +#ifdef SQLITE_DEBUG +/* +** Return the sum of the reference counts for all pages held by pPager. +*/ +int sqlite3PagerRefcount(Pager *pPager){ + return sqlite3PcacheRefCount(pPager->pPCache); +} +#endif + +/* +** Return the approximate number of bytes of memory currently +** used by the pager and its associated cache. +*/ +int sqlite3PagerMemUsed(Pager *pPager){ + int perPageSize = pPager->pageSize + pPager->nExtra + + (int)(sizeof(PgHdr) + 5*sizeof(void*)); + return perPageSize*sqlite3PcachePagecount(pPager->pPCache) + + sqlite3MallocSize(pPager) + + pPager->pageSize; +} + +/* +** Return the number of references to the specified page. +*/ +int sqlite3PagerPageRefcount(DbPage *pPage){ + return sqlite3PcachePageRefcount(pPage); +} + +#ifdef SQLITE_TEST +/* +** This routine is used for testing and analysis only. +*/ +int *sqlite3PagerStats(Pager *pPager){ + static int a[11]; + a[0] = sqlite3PcacheRefCount(pPager->pPCache); + a[1] = sqlite3PcachePagecount(pPager->pPCache); + a[2] = sqlite3PcacheGetCachesize(pPager->pPCache); + a[3] = pPager->eState==PAGER_OPEN ? -1 : (int) pPager->dbSize; + a[4] = pPager->eState; + a[5] = pPager->errCode; + a[6] = (int)pPager->aStat[PAGER_STAT_HIT] & 0x7fffffff; + a[7] = (int)pPager->aStat[PAGER_STAT_MISS] & 0x7fffffff; + a[8] = 0; /* Used to be pPager->nOvfl */ + a[9] = pPager->nRead; + a[10] = (int)pPager->aStat[PAGER_STAT_WRITE] & 0x7fffffff; + return a; +} +#endif + +/* +** Parameter eStat must be one of SQLITE_DBSTATUS_CACHE_HIT, _MISS, _WRITE, +** or _WRITE+1. The SQLITE_DBSTATUS_CACHE_WRITE+1 case is a translation +** of SQLITE_DBSTATUS_CACHE_SPILL. The _SPILL case is not contiguous because +** it was added later. +** +** Before returning, *pnVal is incremented by the +** current cache hit or miss count, according to the value of eStat. If the +** reset parameter is non-zero, the cache hit or miss count is zeroed before +** returning. +*/ +void sqlite3PagerCacheStat(Pager *pPager, int eStat, int reset, u64 *pnVal){ + + assert( eStat==SQLITE_DBSTATUS_CACHE_HIT + || eStat==SQLITE_DBSTATUS_CACHE_MISS + || eStat==SQLITE_DBSTATUS_CACHE_WRITE + || eStat==SQLITE_DBSTATUS_CACHE_WRITE+1 + ); + + assert( SQLITE_DBSTATUS_CACHE_HIT+1==SQLITE_DBSTATUS_CACHE_MISS ); + assert( SQLITE_DBSTATUS_CACHE_HIT+2==SQLITE_DBSTATUS_CACHE_WRITE ); + assert( PAGER_STAT_HIT==0 && PAGER_STAT_MISS==1 + && PAGER_STAT_WRITE==2 && PAGER_STAT_SPILL==3 ); + + eStat -= SQLITE_DBSTATUS_CACHE_HIT; + *pnVal += pPager->aStat[eStat]; + if( reset ){ + pPager->aStat[eStat] = 0; + } +} + +/* +** Return true if this is an in-memory or temp-file backed pager. +*/ +int sqlite3PagerIsMemdb(Pager *pPager){ + return pPager->tempFile || pPager->memVfs; +} + +/* +** Check that there are at least nSavepoint savepoints open. If there are +** currently less than nSavepoints open, then open one or more savepoints +** to make up the difference. If the number of savepoints is already +** equal to nSavepoint, then this function is a no-op. +** +** If a memory allocation fails, SQLITE_NOMEM is returned. If an error +** occurs while opening the sub-journal file, then an IO error code is +** returned. Otherwise, SQLITE_OK. +*/ +static SQLITE_NOINLINE int pagerOpenSavepoint(Pager *pPager, int nSavepoint){ + int rc = SQLITE_OK; /* Return code */ + int nCurrent = pPager->nSavepoint; /* Current number of savepoints */ + int ii; /* Iterator variable */ + PagerSavepoint *aNew; /* New Pager.aSavepoint array */ + + assert( pPager->eState>=PAGER_WRITER_LOCKED ); + assert( assert_pager_state(pPager) ); + assert( nSavepoint>nCurrent && pPager->useJournal ); + + /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM + ** if the allocation fails. Otherwise, zero the new portion in case a + ** malloc failure occurs while populating it in the for(...) loop below. + */ + aNew = (PagerSavepoint *)sqlite3Realloc( + pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint + ); + if( !aNew ){ + return SQLITE_NOMEM_BKPT; + } + memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint)); + pPager->aSavepoint = aNew; + + /* Populate the PagerSavepoint structures just allocated. */ + for(ii=nCurrent; ii<nSavepoint; ii++){ + aNew[ii].nOrig = pPager->dbSize; + if( isOpen(pPager->jfd) && pPager->journalOff>0 ){ + aNew[ii].iOffset = pPager->journalOff; + }else{ + aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager); + } + aNew[ii].iSubRec = pPager->nSubRec; + aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize); + aNew[ii].bTruncateOnRelease = 1; + if( !aNew[ii].pInSavepoint ){ + return SQLITE_NOMEM_BKPT; + } + if( pagerUseWal(pPager) ){ + sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData); + } + pPager->nSavepoint = ii+1; + } + assert( pPager->nSavepoint==nSavepoint ); + assertTruncateConstraint(pPager); + return rc; +} +int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){ + assert( pPager->eState>=PAGER_WRITER_LOCKED ); + assert( assert_pager_state(pPager) ); + + if( nSavepoint>pPager->nSavepoint && pPager->useJournal ){ + return pagerOpenSavepoint(pPager, nSavepoint); + }else{ + return SQLITE_OK; + } +} + + +/* +** This function is called to rollback or release (commit) a savepoint. +** The savepoint to release or rollback need not be the most recently +** created savepoint. +** +** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE. +** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with +** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes +** that have occurred since the specified savepoint was created. +** +** The savepoint to rollback or release is identified by parameter +** iSavepoint. A value of 0 means to operate on the outermost savepoint +** (the first created). A value of (Pager.nSavepoint-1) means operate +** on the most recently created savepoint. If iSavepoint is greater than +** (Pager.nSavepoint-1), then this function is a no-op. +** +** If a negative value is passed to this function, then the current +** transaction is rolled back. This is different to calling +** sqlite3PagerRollback() because this function does not terminate +** the transaction or unlock the database, it just restores the +** contents of the database to its original state. +** +** In any case, all savepoints with an index greater than iSavepoint +** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE), +** then savepoint iSavepoint is also destroyed. +** +** This function may return SQLITE_NOMEM if a memory allocation fails, +** or an IO error code if an IO error occurs while rolling back a +** savepoint. If no errors occur, SQLITE_OK is returned. +*/ +int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){ + int rc = pPager->errCode; + +#ifdef SQLITE_ENABLE_ZIPVFS + if( op==SAVEPOINT_RELEASE ) rc = SQLITE_OK; +#endif + + assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK ); + assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK ); + + if( rc==SQLITE_OK && iSavepoint<pPager->nSavepoint ){ + int ii; /* Iterator variable */ + int nNew; /* Number of remaining savepoints after this op. */ + + /* Figure out how many savepoints will still be active after this + ** operation. Store this value in nNew. Then free resources associated + ** with any savepoints that are destroyed by this operation. + */ + nNew = iSavepoint + (( op==SAVEPOINT_RELEASE ) ? 0 : 1); + for(ii=nNew; ii<pPager->nSavepoint; ii++){ + sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint); + } + pPager->nSavepoint = nNew; + + /* Truncate the sub-journal so that it only includes the parts + ** that are still in use. */ + if( op==SAVEPOINT_RELEASE ){ + PagerSavepoint *pRel = &pPager->aSavepoint[nNew]; + if( pRel->bTruncateOnRelease && isOpen(pPager->sjfd) ){ + /* Only truncate if it is an in-memory sub-journal. */ + if( sqlite3JournalIsInMemory(pPager->sjfd) ){ + i64 sz = (pPager->pageSize+4)*(i64)pRel->iSubRec; + rc = sqlite3OsTruncate(pPager->sjfd, sz); + assert( rc==SQLITE_OK ); + } + pPager->nSubRec = pRel->iSubRec; + } + } + /* Else this is a rollback operation, playback the specified savepoint. + ** If this is a temp-file, it is possible that the journal file has + ** not yet been opened. In this case there have been no changes to + ** the database file, so the playback operation can be skipped. + */ + else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){ + PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1]; + rc = pagerPlaybackSavepoint(pPager, pSavepoint); + assert(rc!=SQLITE_DONE); + } + +#ifdef SQLITE_ENABLE_ZIPVFS + /* If the cache has been modified but the savepoint cannot be rolled + ** back journal_mode=off, put the pager in the error state. This way, + ** if the VFS used by this pager includes ZipVFS, the entire transaction + ** can be rolled back at the ZipVFS level. */ + else if( + pPager->journalMode==PAGER_JOURNALMODE_OFF + && pPager->eState>=PAGER_WRITER_CACHEMOD + ){ + pPager->errCode = SQLITE_ABORT; + pPager->eState = PAGER_ERROR; + setGetterMethod(pPager); + } +#endif + } + + return rc; +} + +/* +** Return the full pathname of the database file. +** +** Except, if the pager is in-memory only, then return an empty string if +** nullIfMemDb is true. This routine is called with nullIfMemDb==1 when +** used to report the filename to the user, for compatibility with legacy +** behavior. But when the Btree needs to know the filename for matching to +** shared cache, it uses nullIfMemDb==0 so that in-memory databases can +** participate in shared-cache. +** +** The return value to this routine is always safe to use with +** sqlite3_uri_parameter() and sqlite3_filename_database() and friends. +*/ +const char *sqlite3PagerFilename(const Pager *pPager, int nullIfMemDb){ + static const char zFake[8] = { 0, 0, 0, 0, 0, 0, 0, 0 }; + if( nullIfMemDb && (pPager->memDb || sqlite3IsMemdb(pPager->pVfs)) ){ + return &zFake[4]; + }else{ + return pPager->zFilename; + } +} + +/* +** Return the VFS structure for the pager. +*/ +sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){ + return pPager->pVfs; +} + +/* +** Return the file handle for the database file associated +** with the pager. This might return NULL if the file has +** not yet been opened. +*/ +sqlite3_file *sqlite3PagerFile(Pager *pPager){ + return pPager->fd; +} + +/* +** Return the file handle for the journal file (if it exists). +** This will be either the rollback journal or the WAL file. +*/ +sqlite3_file *sqlite3PagerJrnlFile(Pager *pPager){ +#if SQLITE_OMIT_WAL + return pPager->jfd; +#else + return pPager->pWal ? sqlite3WalFile(pPager->pWal) : pPager->jfd; +#endif +} + +/* +** Return the full pathname of the journal file. +*/ +const char *sqlite3PagerJournalname(Pager *pPager){ + return pPager->zJournal; +} + +#ifndef SQLITE_OMIT_AUTOVACUUM +/* +** Move the page pPg to location pgno in the file. +** +** There must be no references to the page previously located at +** pgno (which we call pPgOld) though that page is allowed to be +** in cache. If the page previously located at pgno is not already +** in the rollback journal, it is not put there by by this routine. +** +** References to the page pPg remain valid. Updating any +** meta-data associated with pPg (i.e. data stored in the nExtra bytes +** allocated along with the page) is the responsibility of the caller. +** +** A transaction must be active when this routine is called. It used to be +** required that a statement transaction was not active, but this restriction +** has been removed (CREATE INDEX needs to move a page when a statement +** transaction is active). +** +** If the fourth argument, isCommit, is non-zero, then this page is being +** moved as part of a database reorganization just before the transaction +** is being committed. In this case, it is guaranteed that the database page +** pPg refers to will not be written to again within this transaction. +** +** This function may return SQLITE_NOMEM or an IO error code if an error +** occurs. Otherwise, it returns SQLITE_OK. +*/ +int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){ + PgHdr *pPgOld; /* The page being overwritten. */ + Pgno needSyncPgno = 0; /* Old value of pPg->pgno, if sync is required */ + int rc; /* Return code */ + Pgno origPgno; /* The original page number */ + + assert( pPg->nRef>0 ); + assert( pPager->eState==PAGER_WRITER_CACHEMOD + || pPager->eState==PAGER_WRITER_DBMOD + ); + assert( assert_pager_state(pPager) ); + + /* In order to be able to rollback, an in-memory database must journal + ** the page we are moving from. + */ + assert( pPager->tempFile || !MEMDB ); + if( pPager->tempFile ){ + rc = sqlite3PagerWrite(pPg); + if( rc ) return rc; + } + + /* If the page being moved is dirty and has not been saved by the latest + ** savepoint, then save the current contents of the page into the + ** sub-journal now. This is required to handle the following scenario: + ** + ** BEGIN; + ** <journal page X, then modify it in memory> + ** SAVEPOINT one; + ** <Move page X to location Y> + ** ROLLBACK TO one; + ** + ** If page X were not written to the sub-journal here, it would not + ** be possible to restore its contents when the "ROLLBACK TO one" + ** statement were is processed. + ** + ** subjournalPage() may need to allocate space to store pPg->pgno into + ** one or more savepoint bitvecs. This is the reason this function + ** may return SQLITE_NOMEM. + */ + if( (pPg->flags & PGHDR_DIRTY)!=0 + && SQLITE_OK!=(rc = subjournalPageIfRequired(pPg)) + ){ + return rc; + } + + PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n", + PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno)); + IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno)) + + /* If the journal needs to be sync()ed before page pPg->pgno can + ** be written to, store pPg->pgno in local variable needSyncPgno. + ** + ** If the isCommit flag is set, there is no need to remember that + ** the journal needs to be sync()ed before database page pPg->pgno + ** can be written to. The caller has already promised not to write to it. + */ + if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){ + needSyncPgno = pPg->pgno; + assert( pPager->journalMode==PAGER_JOURNALMODE_OFF || + pageInJournal(pPager, pPg) || pPg->pgno>pPager->dbOrigSize ); + assert( pPg->flags&PGHDR_DIRTY ); + } + + /* If the cache contains a page with page-number pgno, remove it + ** from its hash chain. Also, if the PGHDR_NEED_SYNC flag was set for + ** page pgno before the 'move' operation, it needs to be retained + ** for the page moved there. + */ + pPg->flags &= ~PGHDR_NEED_SYNC; + pPgOld = sqlite3PagerLookup(pPager, pgno); + assert( !pPgOld || pPgOld->nRef==1 || CORRUPT_DB ); + if( pPgOld ){ + if( NEVER(pPgOld->nRef>1) ){ + sqlite3PagerUnrefNotNull(pPgOld); + return SQLITE_CORRUPT_BKPT; + } + pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC); + if( pPager->tempFile ){ + /* Do not discard pages from an in-memory database since we might + ** need to rollback later. Just move the page out of the way. */ + sqlite3PcacheMove(pPgOld, pPager->dbSize+1); + }else{ + sqlite3PcacheDrop(pPgOld); + } + } + + origPgno = pPg->pgno; + sqlite3PcacheMove(pPg, pgno); + sqlite3PcacheMakeDirty(pPg); + + /* For an in-memory database, make sure the original page continues + ** to exist, in case the transaction needs to roll back. Use pPgOld + ** as the original page since it has already been allocated. + */ + if( pPager->tempFile && pPgOld ){ + sqlite3PcacheMove(pPgOld, origPgno); + sqlite3PagerUnrefNotNull(pPgOld); + } + + if( needSyncPgno ){ + /* If needSyncPgno is non-zero, then the journal file needs to be + ** sync()ed before any data is written to database file page needSyncPgno. + ** Currently, no such page exists in the page-cache and the + ** "is journaled" bitvec flag has been set. This needs to be remedied by + ** loading the page into the pager-cache and setting the PGHDR_NEED_SYNC + ** flag. + ** + ** If the attempt to load the page into the page-cache fails, (due + ** to a malloc() or IO failure), clear the bit in the pInJournal[] + ** array. Otherwise, if the page is loaded and written again in + ** this transaction, it may be written to the database file before + ** it is synced into the journal file. This way, it may end up in + ** the journal file twice, but that is not a problem. + */ + PgHdr *pPgHdr; + rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr, 0); + if( rc!=SQLITE_OK ){ + if( needSyncPgno<=pPager->dbOrigSize ){ + assert( pPager->pTmpSpace!=0 ); + sqlite3BitvecClear(pPager->pInJournal, needSyncPgno, pPager->pTmpSpace); + } + return rc; + } + pPgHdr->flags |= PGHDR_NEED_SYNC; + sqlite3PcacheMakeDirty(pPgHdr); + sqlite3PagerUnrefNotNull(pPgHdr); + } + + return SQLITE_OK; +} +#endif + +/* +** The page handle passed as the first argument refers to a dirty page +** with a page number other than iNew. This function changes the page's +** page number to iNew and sets the value of the PgHdr.flags field to +** the value passed as the third parameter. +*/ +void sqlite3PagerRekey(DbPage *pPg, Pgno iNew, u16 flags){ + assert( pPg->pgno!=iNew ); + pPg->flags = flags; + sqlite3PcacheMove(pPg, iNew); +} + +/* +** Return a pointer to the data for the specified page. +*/ +void *sqlite3PagerGetData(DbPage *pPg){ + assert( pPg->nRef>0 || pPg->pPager->memDb ); + return pPg->pData; +} + +/* +** Return a pointer to the Pager.nExtra bytes of "extra" space +** allocated along with the specified page. +*/ +void *sqlite3PagerGetExtra(DbPage *pPg){ + return pPg->pExtra; +} + +/* +** Get/set the locking-mode for this pager. Parameter eMode must be one +** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or +** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then +** the locking-mode is set to the value specified. +** +** The returned value is either PAGER_LOCKINGMODE_NORMAL or +** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated) +** locking-mode. +*/ +int sqlite3PagerLockingMode(Pager *pPager, int eMode){ + assert( eMode==PAGER_LOCKINGMODE_QUERY + || eMode==PAGER_LOCKINGMODE_NORMAL + || eMode==PAGER_LOCKINGMODE_EXCLUSIVE ); + assert( PAGER_LOCKINGMODE_QUERY<0 ); + assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 ); + assert( pPager->exclusiveMode || 0==sqlite3WalHeapMemory(pPager->pWal) ); + if( eMode>=0 && !pPager->tempFile && !sqlite3WalHeapMemory(pPager->pWal) ){ + pPager->exclusiveMode = (u8)eMode; + } + return (int)pPager->exclusiveMode; +} + +/* +** Set the journal-mode for this pager. Parameter eMode must be one of: +** +** PAGER_JOURNALMODE_DELETE +** PAGER_JOURNALMODE_TRUNCATE +** PAGER_JOURNALMODE_PERSIST +** PAGER_JOURNALMODE_OFF +** PAGER_JOURNALMODE_MEMORY +** PAGER_JOURNALMODE_WAL +** +** The journalmode is set to the value specified if the change is allowed. +** The change may be disallowed for the following reasons: +** +** * An in-memory database can only have its journal_mode set to _OFF +** or _MEMORY. +** +** * Temporary databases cannot have _WAL journalmode. +** +** The returned indicate the current (possibly updated) journal-mode. +*/ +int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){ + u8 eOld = pPager->journalMode; /* Prior journalmode */ + + /* The eMode parameter is always valid */ + assert( eMode==PAGER_JOURNALMODE_DELETE /* 0 */ + || eMode==PAGER_JOURNALMODE_PERSIST /* 1 */ + || eMode==PAGER_JOURNALMODE_OFF /* 2 */ + || eMode==PAGER_JOURNALMODE_TRUNCATE /* 3 */ + || eMode==PAGER_JOURNALMODE_MEMORY /* 4 */ + || eMode==PAGER_JOURNALMODE_WAL /* 5 */ ); + + /* This routine is only called from the OP_JournalMode opcode, and + ** the logic there will never allow a temporary file to be changed + ** to WAL mode. + */ + assert( pPager->tempFile==0 || eMode!=PAGER_JOURNALMODE_WAL ); + + /* Do allow the journalmode of an in-memory database to be set to + ** anything other than MEMORY or OFF + */ + if( MEMDB ){ + assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF ); + if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){ + eMode = eOld; + } + } + + if( eMode!=eOld ){ + + /* Change the journal mode. */ + assert( pPager->eState!=PAGER_ERROR ); + pPager->journalMode = (u8)eMode; + + /* When transitioning from TRUNCATE or PERSIST to any other journal + ** mode except WAL, unless the pager is in locking_mode=exclusive mode, + ** delete the journal file. + */ + assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 ); + assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 ); + assert( (PAGER_JOURNALMODE_DELETE & 5)==0 ); + assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 ); + assert( (PAGER_JOURNALMODE_OFF & 5)==0 ); + assert( (PAGER_JOURNALMODE_WAL & 5)==5 ); + + assert( isOpen(pPager->fd) || pPager->exclusiveMode ); + if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){ + /* In this case we would like to delete the journal file. If it is + ** not possible, then that is not a problem. Deleting the journal file + ** here is an optimization only. + ** + ** Before deleting the journal file, obtain a RESERVED lock on the + ** database file. This ensures that the journal file is not deleted + ** while it is in use by some other client. + */ + sqlite3OsClose(pPager->jfd); + if( pPager->eLock>=RESERVED_LOCK ){ + sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0); + }else{ + int rc = SQLITE_OK; + int state = pPager->eState; + assert( state==PAGER_OPEN || state==PAGER_READER ); + if( state==PAGER_OPEN ){ + rc = sqlite3PagerSharedLock(pPager); + } + if( pPager->eState==PAGER_READER ){ + assert( rc==SQLITE_OK ); + rc = pagerLockDb(pPager, RESERVED_LOCK); + } + if( rc==SQLITE_OK ){ + sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0); + } + if( rc==SQLITE_OK && state==PAGER_READER ){ + pagerUnlockDb(pPager, SHARED_LOCK); + }else if( state==PAGER_OPEN ){ + pager_unlock(pPager); + } + assert( state==pPager->eState ); + } + }else if( eMode==PAGER_JOURNALMODE_OFF || eMode==PAGER_JOURNALMODE_MEMORY ){ + sqlite3OsClose(pPager->jfd); + } + } + + /* Return the new journal mode */ + return (int)pPager->journalMode; +} + +/* +** Return the current journal mode. +*/ +int sqlite3PagerGetJournalMode(Pager *pPager){ + return (int)pPager->journalMode; +} + +/* +** Return TRUE if the pager is in a state where it is OK to change the +** journalmode. Journalmode changes can only happen when the database +** is unmodified. +*/ +int sqlite3PagerOkToChangeJournalMode(Pager *pPager){ + assert( assert_pager_state(pPager) ); + if( pPager->eState>=PAGER_WRITER_CACHEMOD ) return 0; + if( NEVER(isOpen(pPager->jfd) && pPager->journalOff>0) ) return 0; + return 1; +} + +/* +** Get/set the size-limit used for persistent journal files. +** +** Setting the size limit to -1 means no limit is enforced. +** An attempt to set a limit smaller than -1 is a no-op. +*/ +i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){ + if( iLimit>=-1 ){ + pPager->journalSizeLimit = iLimit; + sqlite3WalLimit(pPager->pWal, iLimit); + } + return pPager->journalSizeLimit; +} + +/* +** Return a pointer to the pPager->pBackup variable. The backup module +** in backup.c maintains the content of this variable. This module +** uses it opaquely as an argument to sqlite3BackupRestart() and +** sqlite3BackupUpdate() only. +*/ +sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){ + return &pPager->pBackup; +} + +#ifndef SQLITE_OMIT_VACUUM +/* +** Unless this is an in-memory or temporary database, clear the pager cache. +*/ +void sqlite3PagerClearCache(Pager *pPager){ + assert( MEMDB==0 || pPager->tempFile ); + if( pPager->tempFile==0 ) pager_reset(pPager); +} +#endif + + +#ifndef SQLITE_OMIT_WAL +/* +** This function is called when the user invokes "PRAGMA wal_checkpoint", +** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint() +** or wal_blocking_checkpoint() API functions. +** +** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART. +*/ +int sqlite3PagerCheckpoint( + Pager *pPager, /* Checkpoint on this pager */ + sqlite3 *db, /* Db handle used to check for interrupts */ + int eMode, /* Type of checkpoint */ + int *pnLog, /* OUT: Final number of frames in log */ + int *pnCkpt /* OUT: Final number of checkpointed frames */ +){ + int rc = SQLITE_OK; + if( pPager->pWal==0 && pPager->journalMode==PAGER_JOURNALMODE_WAL ){ + /* This only happens when a database file is zero bytes in size opened and + ** then "PRAGMA journal_mode=WAL" is run and then sqlite3_wal_checkpoint() + ** is invoked without any intervening transactions. We need to start + ** a transaction to initialize pWal. The PRAGMA table_list statement is + ** used for this since it starts transactions on every database file, + ** including all ATTACHed databases. This seems expensive for a single + ** sqlite3_wal_checkpoint() call, but it happens very rarely. + ** https://sqlite.org/forum/forumpost/fd0f19d229156939 + */ + sqlite3_exec(db, "PRAGMA table_list",0,0,0); + } + if( pPager->pWal ){ + rc = sqlite3WalCheckpoint(pPager->pWal, db, eMode, + (eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler), + pPager->pBusyHandlerArg, + pPager->walSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace, + pnLog, pnCkpt + ); + } + return rc; +} + +int sqlite3PagerWalCallback(Pager *pPager){ + return sqlite3WalCallback(pPager->pWal); +} + +/* +** Return true if the underlying VFS for the given pager supports the +** primitives necessary for write-ahead logging. +*/ +int sqlite3PagerWalSupported(Pager *pPager){ + const sqlite3_io_methods *pMethods = pPager->fd->pMethods; + if( pPager->noLock ) return 0; + return pPager->exclusiveMode || (pMethods->iVersion>=2 && pMethods->xShmMap); +} + +/* +** Attempt to take an exclusive lock on the database file. If a PENDING lock +** is obtained instead, immediately release it. +*/ +static int pagerExclusiveLock(Pager *pPager){ + int rc; /* Return code */ + u8 eOrigLock; /* Original lock */ + + assert( pPager->eLock>=SHARED_LOCK ); + eOrigLock = pPager->eLock; + rc = pagerLockDb(pPager, EXCLUSIVE_LOCK); + if( rc!=SQLITE_OK ){ + /* If the attempt to grab the exclusive lock failed, release the + ** pending lock that may have been obtained instead. */ + pagerUnlockDb(pPager, eOrigLock); + } + + return rc; +} + +/* +** Call sqlite3WalOpen() to open the WAL handle. If the pager is in +** exclusive-locking mode when this function is called, take an EXCLUSIVE +** lock on the database file and use heap-memory to store the wal-index +** in. Otherwise, use the normal shared-memory. +*/ +static int pagerOpenWal(Pager *pPager){ + int rc = SQLITE_OK; + + assert( pPager->pWal==0 && pPager->tempFile==0 ); + assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK ); + + /* If the pager is already in exclusive-mode, the WAL module will use + ** heap-memory for the wal-index instead of the VFS shared-memory + ** implementation. Take the exclusive lock now, before opening the WAL + ** file, to make sure this is safe. + */ + if( pPager->exclusiveMode ){ + rc = pagerExclusiveLock(pPager); + } + + /* Open the connection to the log file. If this operation fails, + ** (e.g. due to malloc() failure), return an error code. + */ + if( rc==SQLITE_OK ){ + rc = sqlite3WalOpen(pPager->pVfs, + pPager->fd, pPager->zWal, pPager->exclusiveMode, + pPager->journalSizeLimit, &pPager->pWal + ); + } + pagerFixMaplimit(pPager); + + return rc; +} + + +/* +** The caller must be holding a SHARED lock on the database file to call +** this function. +** +** If the pager passed as the first argument is open on a real database +** file (not a temp file or an in-memory database), and the WAL file +** is not already open, make an attempt to open it now. If successful, +** return SQLITE_OK. If an error occurs or the VFS used by the pager does +** not support the xShmXXX() methods, return an error code. *pbOpen is +** not modified in either case. +** +** If the pager is open on a temp-file (or in-memory database), or if +** the WAL file is already open, set *pbOpen to 1 and return SQLITE_OK +** without doing anything. +*/ +int sqlite3PagerOpenWal( + Pager *pPager, /* Pager object */ + int *pbOpen /* OUT: Set to true if call is a no-op */ +){ + int rc = SQLITE_OK; /* Return code */ + + assert( assert_pager_state(pPager) ); + assert( pPager->eState==PAGER_OPEN || pbOpen ); + assert( pPager->eState==PAGER_READER || !pbOpen ); + assert( pbOpen==0 || *pbOpen==0 ); + assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) ); + + if( !pPager->tempFile && !pPager->pWal ){ + if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN; + + /* Close any rollback journal previously open */ + sqlite3OsClose(pPager->jfd); + + rc = pagerOpenWal(pPager); + if( rc==SQLITE_OK ){ + pPager->journalMode = PAGER_JOURNALMODE_WAL; + pPager->eState = PAGER_OPEN; + } + }else{ + *pbOpen = 1; + } + + return rc; +} + +/* +** This function is called to close the connection to the log file prior +** to switching from WAL to rollback mode. +** +** Before closing the log file, this function attempts to take an +** EXCLUSIVE lock on the database file. If this cannot be obtained, an +** error (SQLITE_BUSY) is returned and the log connection is not closed. +** If successful, the EXCLUSIVE lock is not released before returning. +*/ +int sqlite3PagerCloseWal(Pager *pPager, sqlite3 *db){ + int rc = SQLITE_OK; + + assert( pPager->journalMode==PAGER_JOURNALMODE_WAL ); + + /* If the log file is not already open, but does exist in the file-system, + ** it may need to be checkpointed before the connection can switch to + ** rollback mode. Open it now so this can happen. + */ + if( !pPager->pWal ){ + int logexists = 0; + rc = pagerLockDb(pPager, SHARED_LOCK); + if( rc==SQLITE_OK ){ + rc = sqlite3OsAccess( + pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &logexists + ); + } + if( rc==SQLITE_OK && logexists ){ + rc = pagerOpenWal(pPager); + } + } + + /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on + ** the database file, the log and log-summary files will be deleted. + */ + if( rc==SQLITE_OK && pPager->pWal ){ + rc = pagerExclusiveLock(pPager); + if( rc==SQLITE_OK ){ + rc = sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags, + pPager->pageSize, (u8*)pPager->pTmpSpace); + pPager->pWal = 0; + pagerFixMaplimit(pPager); + if( rc && !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK); + } + } + return rc; +} + +#ifdef SQLITE_ENABLE_SETLK_TIMEOUT +/* +** If pager pPager is a wal-mode database not in exclusive locking mode, +** invoke the sqlite3WalWriteLock() function on the associated Wal object +** with the same db and bLock parameters as were passed to this function. +** Return an SQLite error code if an error occurs, or SQLITE_OK otherwise. +*/ +int sqlite3PagerWalWriteLock(Pager *pPager, int bLock){ + int rc = SQLITE_OK; + if( pagerUseWal(pPager) && pPager->exclusiveMode==0 ){ + rc = sqlite3WalWriteLock(pPager->pWal, bLock); + } + return rc; +} + +/* +** Set the database handle used by the wal layer to determine if +** blocking locks are required. +*/ +void sqlite3PagerWalDb(Pager *pPager, sqlite3 *db){ + if( pagerUseWal(pPager) ){ + sqlite3WalDb(pPager->pWal, db); + } +} +#endif + +#ifdef SQLITE_ENABLE_SNAPSHOT +/* +** If this is a WAL database, obtain a snapshot handle for the snapshot +** currently open. Otherwise, return an error. +*/ +int sqlite3PagerSnapshotGet(Pager *pPager, sqlite3_snapshot **ppSnapshot){ + int rc = SQLITE_ERROR; + if( pPager->pWal ){ + rc = sqlite3WalSnapshotGet(pPager->pWal, ppSnapshot); + } + return rc; +} + +/* +** If this is a WAL database, store a pointer to pSnapshot. Next time a +** read transaction is opened, attempt to read from the snapshot it +** identifies. If this is not a WAL database, return an error. +*/ +int sqlite3PagerSnapshotOpen( + Pager *pPager, + sqlite3_snapshot *pSnapshot +){ + int rc = SQLITE_OK; + if( pPager->pWal ){ + sqlite3WalSnapshotOpen(pPager->pWal, pSnapshot); + }else{ + rc = SQLITE_ERROR; + } + return rc; +} + +/* +** If this is a WAL database, call sqlite3WalSnapshotRecover(). If this +** is not a WAL database, return an error. +*/ +int sqlite3PagerSnapshotRecover(Pager *pPager){ + int rc; + if( pPager->pWal ){ + rc = sqlite3WalSnapshotRecover(pPager->pWal); + }else{ + rc = SQLITE_ERROR; + } + return rc; +} + +/* +** The caller currently has a read transaction open on the database. +** If this is not a WAL database, SQLITE_ERROR is returned. Otherwise, +** this function takes a SHARED lock on the CHECKPOINTER slot and then +** checks if the snapshot passed as the second argument is still +** available. If so, SQLITE_OK is returned. +** +** If the snapshot is not available, SQLITE_ERROR is returned. Or, if +** the CHECKPOINTER lock cannot be obtained, SQLITE_BUSY. If any error +** occurs (any value other than SQLITE_OK is returned), the CHECKPOINTER +** lock is released before returning. +*/ +int sqlite3PagerSnapshotCheck(Pager *pPager, sqlite3_snapshot *pSnapshot){ + int rc; + if( pPager->pWal ){ + rc = sqlite3WalSnapshotCheck(pPager->pWal, pSnapshot); + }else{ + rc = SQLITE_ERROR; + } + return rc; +} + +/* +** Release a lock obtained by an earlier successful call to +** sqlite3PagerSnapshotCheck(). +*/ +void sqlite3PagerSnapshotUnlock(Pager *pPager){ + assert( pPager->pWal ); + sqlite3WalSnapshotUnlock(pPager->pWal); +} + +#endif /* SQLITE_ENABLE_SNAPSHOT */ +#endif /* !SQLITE_OMIT_WAL */ + +#ifdef SQLITE_ENABLE_ZIPVFS +/* +** A read-lock must be held on the pager when this function is called. If +** the pager is in WAL mode and the WAL file currently contains one or more +** frames, return the size in bytes of the page images stored within the +** WAL frames. Otherwise, if this is not a WAL database or the WAL file +** is empty, return 0. +*/ +int sqlite3PagerWalFramesize(Pager *pPager){ + assert( pPager->eState>=PAGER_READER ); + return sqlite3WalFramesize(pPager->pWal); +} +#endif + +#if defined(SQLITE_USE_SEH) && !defined(SQLITE_OMIT_WAL) +int sqlite3PagerWalSystemErrno(Pager *pPager){ + return sqlite3WalSystemErrno(pPager->pWal); +} +#endif + +#endif /* SQLITE_OMIT_DISKIO */ |