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Diffstat (limited to 'src/pcache.h')
| -rw-r--r-- | src/pcache.h | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/src/pcache.h b/src/pcache.h new file mode 100644 index 0000000..eb55396 --- /dev/null +++ b/src/pcache.h @@ -0,0 +1,190 @@ +/* +** 2008 August 05 +** +** 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 header file defines the interface that the sqlite page cache +** subsystem. +*/ + +#ifndef _PCACHE_H_ + +typedef struct PgHdr PgHdr; +typedef struct PCache PCache; + +/* +** Every page in the cache is controlled by an instance of the following +** structure. +*/ +struct PgHdr { + sqlite3_pcache_page *pPage; /* Pcache object page handle */ + void *pData; /* Page data */ + void *pExtra; /* Extra content */ + PCache *pCache; /* PRIVATE: Cache that owns this page */ + PgHdr *pDirty; /* Transient list of dirty sorted by pgno */ + Pager *pPager; /* The pager this page is part of */ + Pgno pgno; /* Page number for this page */ +#ifdef SQLITE_CHECK_PAGES + u32 pageHash; /* Hash of page content */ +#endif + u16 flags; /* PGHDR flags defined below */ + + /********************************************************************** + ** Elements above, except pCache, are public. All that follow are + ** private to pcache.c and should not be accessed by other modules. + ** pCache is grouped with the public elements for efficiency. + */ + i16 nRef; /* Number of users of this page */ + PgHdr *pDirtyNext; /* Next element in list of dirty pages */ + PgHdr *pDirtyPrev; /* Previous element in list of dirty pages */ + /* NB: pDirtyNext and pDirtyPrev are undefined if the + ** PgHdr object is not dirty */ +}; + +/* Bit values for PgHdr.flags */ +#define PGHDR_CLEAN 0x001 /* Page not on the PCache.pDirty list */ +#define PGHDR_DIRTY 0x002 /* Page is on the PCache.pDirty list */ +#define PGHDR_WRITEABLE 0x004 /* Journaled and ready to modify */ +#define PGHDR_NEED_SYNC 0x008 /* Fsync the rollback journal before + ** writing this page to the database */ +#define PGHDR_DONT_WRITE 0x010 /* Do not write content to disk */ +#define PGHDR_MMAP 0x020 /* This is an mmap page object */ + +#define PGHDR_WAL_APPEND 0x040 /* Appended to wal file */ + +/* Initialize and shutdown the page cache subsystem */ +int sqlite3PcacheInitialize(void); +void sqlite3PcacheShutdown(void); + +/* Page cache buffer management: +** These routines implement SQLITE_CONFIG_PAGECACHE. +*/ +void sqlite3PCacheBufferSetup(void *, int sz, int n); + +/* Create a new pager cache. +** Under memory stress, invoke xStress to try to make pages clean. +** Only clean and unpinned pages can be reclaimed. +*/ +int sqlite3PcacheOpen( + int szPage, /* Size of every page */ + int szExtra, /* Extra space associated with each page */ + int bPurgeable, /* True if pages are on backing store */ + int (*xStress)(void*, PgHdr*), /* Call to try to make pages clean */ + void *pStress, /* Argument to xStress */ + PCache *pToInit /* Preallocated space for the PCache */ +); + +/* Modify the page-size after the cache has been created. */ +int sqlite3PcacheSetPageSize(PCache *, int); + +/* Return the size in bytes of a PCache object. Used to preallocate +** storage space. +*/ +int sqlite3PcacheSize(void); + +/* One release per successful fetch. Page is pinned until released. +** Reference counted. +*/ +sqlite3_pcache_page *sqlite3PcacheFetch(PCache*, Pgno, int createFlag); +int sqlite3PcacheFetchStress(PCache*, Pgno, sqlite3_pcache_page**); +PgHdr *sqlite3PcacheFetchFinish(PCache*, Pgno, sqlite3_pcache_page *pPage); +void sqlite3PcacheRelease(PgHdr*); + +void sqlite3PcacheDrop(PgHdr*); /* Remove page from cache */ +void sqlite3PcacheMakeDirty(PgHdr*); /* Make sure page is marked dirty */ +void sqlite3PcacheMakeClean(PgHdr*); /* Mark a single page as clean */ +void sqlite3PcacheCleanAll(PCache*); /* Mark all dirty list pages as clean */ +void sqlite3PcacheClearWritable(PCache*); + +/* Change a page number. Used by incr-vacuum. */ +void sqlite3PcacheMove(PgHdr*, Pgno); + +/* Remove all pages with pgno>x. Reset the cache if x==0 */ +void sqlite3PcacheTruncate(PCache*, Pgno x); + +/* Get a list of all dirty pages in the cache, sorted by page number */ +PgHdr *sqlite3PcacheDirtyList(PCache*); + +/* Reset and close the cache object */ +void sqlite3PcacheClose(PCache*); + +/* Clear flags from pages of the page cache */ +void sqlite3PcacheClearSyncFlags(PCache *); + +/* Discard the contents of the cache */ +void sqlite3PcacheClear(PCache*); + +/* Return the total number of outstanding page references */ +int sqlite3PcacheRefCount(PCache*); + +/* Increment the reference count of an existing page */ +void sqlite3PcacheRef(PgHdr*); + +int sqlite3PcachePageRefcount(PgHdr*); + +/* Return the total number of pages stored in the cache */ +int sqlite3PcachePagecount(PCache*); + +#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG) +/* Iterate through all dirty pages currently stored in the cache. This +** interface is only available if SQLITE_CHECK_PAGES is defined when the +** library is built. +*/ +void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)); +#endif + +#if defined(SQLITE_DEBUG) +/* Check invariants on a PgHdr object */ +int sqlite3PcachePageSanity(PgHdr*); +#endif + +/* Set and get the suggested cache-size for the specified pager-cache. +** +** If no global maximum is configured, then the system attempts to limit +** the total number of pages cached by purgeable pager-caches to the sum +** of the suggested cache-sizes. +*/ +void sqlite3PcacheSetCachesize(PCache *, int); +#ifdef SQLITE_TEST +int sqlite3PcacheGetCachesize(PCache *); +#endif + +/* Set or get the suggested spill-size for the specified pager-cache. +** +** The spill-size is the minimum number of pages in cache before the cache +** will attempt to spill dirty pages by calling xStress. +*/ +int sqlite3PcacheSetSpillsize(PCache *, int); + +/* Free up as much memory as possible from the page cache */ +void sqlite3PcacheShrink(PCache*); + +#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT +/* Try to return memory used by the pcache module to the main memory heap */ +int sqlite3PcacheReleaseMemory(int); +#endif + +#ifdef SQLITE_TEST +void sqlite3PcacheStats(int*,int*,int*,int*); +#endif + +void sqlite3PCacheSetDefault(void); + +/* Return the header size */ +int sqlite3HeaderSizePcache(void); +int sqlite3HeaderSizePcache1(void); + +/* Number of dirty pages as a percentage of the configured cache size */ +int sqlite3PCachePercentDirty(PCache*); + +#ifdef SQLITE_DIRECT_OVERFLOW_READ +int sqlite3PCacheIsDirty(PCache *pCache); +#endif + +#endif /* _PCACHE_H_ */ |