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Diffstat (limited to 'src/dbpage.c')
| -rw-r--r-- | src/dbpage.c | 435 |
1 files changed, 435 insertions, 0 deletions
diff --git a/src/dbpage.c b/src/dbpage.c new file mode 100644 index 0000000..73c31f0 --- /dev/null +++ b/src/dbpage.c @@ -0,0 +1,435 @@ +/* +** 2017-10-11 +** +** 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 file contains an implementation of the "sqlite_dbpage" virtual table. +** +** The sqlite_dbpage virtual table is used to read or write whole raw +** pages of the database file. The pager interface is used so that +** uncommitted changes and changes recorded in the WAL file are correctly +** retrieved. +** +** Usage example: +** +** SELECT data FROM sqlite_dbpage('aux1') WHERE pgno=123; +** +** This is an eponymous virtual table so it does not need to be created before +** use. The optional argument to the sqlite_dbpage() table name is the +** schema for the database file that is to be read. The default schema is +** "main". +** +** The data field of sqlite_dbpage table can be updated. The new +** value must be a BLOB which is the correct page size, otherwise the +** update fails. Rows may not be deleted or inserted. +*/ + +#include "sqliteInt.h" /* Requires access to internal data structures */ +#if (defined(SQLITE_ENABLE_DBPAGE_VTAB) || defined(SQLITE_TEST)) \ + && !defined(SQLITE_OMIT_VIRTUALTABLE) + +typedef struct DbpageTable DbpageTable; +typedef struct DbpageCursor DbpageCursor; + +struct DbpageCursor { + sqlite3_vtab_cursor base; /* Base class. Must be first */ + int pgno; /* Current page number */ + int mxPgno; /* Last page to visit on this scan */ + Pager *pPager; /* Pager being read/written */ + DbPage *pPage1; /* Page 1 of the database */ + int iDb; /* Index of database to analyze */ + int szPage; /* Size of each page in bytes */ +}; + +struct DbpageTable { + sqlite3_vtab base; /* Base class. Must be first */ + sqlite3 *db; /* The database */ +}; + +/* Columns */ +#define DBPAGE_COLUMN_PGNO 0 +#define DBPAGE_COLUMN_DATA 1 +#define DBPAGE_COLUMN_SCHEMA 2 + + + +/* +** Connect to or create a dbpagevfs virtual table. +*/ +static int dbpageConnect( + sqlite3 *db, + void *pAux, + int argc, const char *const*argv, + sqlite3_vtab **ppVtab, + char **pzErr +){ + DbpageTable *pTab = 0; + int rc = SQLITE_OK; + (void)pAux; + (void)argc; + (void)argv; + (void)pzErr; + + sqlite3_vtab_config(db, SQLITE_VTAB_DIRECTONLY); + sqlite3_vtab_config(db, SQLITE_VTAB_USES_ALL_SCHEMAS); + rc = sqlite3_declare_vtab(db, + "CREATE TABLE x(pgno INTEGER PRIMARY KEY, data BLOB, schema HIDDEN)"); + if( rc==SQLITE_OK ){ + pTab = (DbpageTable *)sqlite3_malloc64(sizeof(DbpageTable)); + if( pTab==0 ) rc = SQLITE_NOMEM_BKPT; + } + + assert( rc==SQLITE_OK || pTab==0 ); + if( rc==SQLITE_OK ){ + memset(pTab, 0, sizeof(DbpageTable)); + pTab->db = db; + } + + *ppVtab = (sqlite3_vtab*)pTab; + return rc; +} + +/* +** Disconnect from or destroy a dbpagevfs virtual table. +*/ +static int dbpageDisconnect(sqlite3_vtab *pVtab){ + sqlite3_free(pVtab); + return SQLITE_OK; +} + +/* +** idxNum: +** +** 0 schema=main, full table scan +** 1 schema=main, pgno=?1 +** 2 schema=?1, full table scan +** 3 schema=?1, pgno=?2 +*/ +static int dbpageBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){ + int i; + int iPlan = 0; + (void)tab; + + /* If there is a schema= constraint, it must be honored. Report a + ** ridiculously large estimated cost if the schema= constraint is + ** unavailable + */ + for(i=0; i<pIdxInfo->nConstraint; i++){ + struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i]; + if( p->iColumn!=DBPAGE_COLUMN_SCHEMA ) continue; + if( p->op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue; + if( !p->usable ){ + /* No solution. */ + return SQLITE_CONSTRAINT; + } + iPlan = 2; + pIdxInfo->aConstraintUsage[i].argvIndex = 1; + pIdxInfo->aConstraintUsage[i].omit = 1; + break; + } + + /* If we reach this point, it means that either there is no schema= + ** constraint (in which case we use the "main" schema) or else the + ** schema constraint was accepted. Lower the estimated cost accordingly + */ + pIdxInfo->estimatedCost = 1.0e6; + + /* Check for constraints against pgno */ + for(i=0; i<pIdxInfo->nConstraint; i++){ + struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i]; + if( p->usable && p->iColumn<=0 && p->op==SQLITE_INDEX_CONSTRAINT_EQ ){ + pIdxInfo->estimatedRows = 1; + pIdxInfo->idxFlags = SQLITE_INDEX_SCAN_UNIQUE; + pIdxInfo->estimatedCost = 1.0; + pIdxInfo->aConstraintUsage[i].argvIndex = iPlan ? 2 : 1; + pIdxInfo->aConstraintUsage[i].omit = 1; + iPlan |= 1; + break; + } + } + pIdxInfo->idxNum = iPlan; + + if( pIdxInfo->nOrderBy>=1 + && pIdxInfo->aOrderBy[0].iColumn<=0 + && pIdxInfo->aOrderBy[0].desc==0 + ){ + pIdxInfo->orderByConsumed = 1; + } + return SQLITE_OK; +} + +/* +** Open a new dbpagevfs cursor. +*/ +static int dbpageOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){ + DbpageCursor *pCsr; + + pCsr = (DbpageCursor *)sqlite3_malloc64(sizeof(DbpageCursor)); + if( pCsr==0 ){ + return SQLITE_NOMEM_BKPT; + }else{ + memset(pCsr, 0, sizeof(DbpageCursor)); + pCsr->base.pVtab = pVTab; + pCsr->pgno = -1; + } + + *ppCursor = (sqlite3_vtab_cursor *)pCsr; + return SQLITE_OK; +} + +/* +** Close a dbpagevfs cursor. +*/ +static int dbpageClose(sqlite3_vtab_cursor *pCursor){ + DbpageCursor *pCsr = (DbpageCursor *)pCursor; + if( pCsr->pPage1 ) sqlite3PagerUnrefPageOne(pCsr->pPage1); + sqlite3_free(pCsr); + return SQLITE_OK; +} + +/* +** Move a dbpagevfs cursor to the next entry in the file. +*/ +static int dbpageNext(sqlite3_vtab_cursor *pCursor){ + int rc = SQLITE_OK; + DbpageCursor *pCsr = (DbpageCursor *)pCursor; + pCsr->pgno++; + return rc; +} + +static int dbpageEof(sqlite3_vtab_cursor *pCursor){ + DbpageCursor *pCsr = (DbpageCursor *)pCursor; + return pCsr->pgno > pCsr->mxPgno; +} + +/* +** idxNum: +** +** 0 schema=main, full table scan +** 1 schema=main, pgno=?1 +** 2 schema=?1, full table scan +** 3 schema=?1, pgno=?2 +** +** idxStr is not used +*/ +static int dbpageFilter( + sqlite3_vtab_cursor *pCursor, + int idxNum, const char *idxStr, + int argc, sqlite3_value **argv +){ + DbpageCursor *pCsr = (DbpageCursor *)pCursor; + DbpageTable *pTab = (DbpageTable *)pCursor->pVtab; + int rc; + sqlite3 *db = pTab->db; + Btree *pBt; + + (void)idxStr; + + /* Default setting is no rows of result */ + pCsr->pgno = 1; + pCsr->mxPgno = 0; + + if( idxNum & 2 ){ + const char *zSchema; + assert( argc>=1 ); + zSchema = (const char*)sqlite3_value_text(argv[0]); + pCsr->iDb = sqlite3FindDbName(db, zSchema); + if( pCsr->iDb<0 ) return SQLITE_OK; + }else{ + pCsr->iDb = 0; + } + pBt = db->aDb[pCsr->iDb].pBt; + if( NEVER(pBt==0) ) return SQLITE_OK; + pCsr->pPager = sqlite3BtreePager(pBt); + pCsr->szPage = sqlite3BtreeGetPageSize(pBt); + pCsr->mxPgno = sqlite3BtreeLastPage(pBt); + if( idxNum & 1 ){ + assert( argc>(idxNum>>1) ); + pCsr->pgno = sqlite3_value_int(argv[idxNum>>1]); + if( pCsr->pgno<1 || pCsr->pgno>pCsr->mxPgno ){ + pCsr->pgno = 1; + pCsr->mxPgno = 0; + }else{ + pCsr->mxPgno = pCsr->pgno; + } + }else{ + assert( pCsr->pgno==1 ); + } + if( pCsr->pPage1 ) sqlite3PagerUnrefPageOne(pCsr->pPage1); + rc = sqlite3PagerGet(pCsr->pPager, 1, &pCsr->pPage1, 0); + return rc; +} + +static int dbpageColumn( + sqlite3_vtab_cursor *pCursor, + sqlite3_context *ctx, + int i +){ + DbpageCursor *pCsr = (DbpageCursor *)pCursor; + int rc = SQLITE_OK; + switch( i ){ + case 0: { /* pgno */ + sqlite3_result_int(ctx, pCsr->pgno); + break; + } + case 1: { /* data */ + DbPage *pDbPage = 0; + if( pCsr->pgno==((PENDING_BYTE/pCsr->szPage)+1) ){ + /* The pending byte page. Assume it is zeroed out. Attempting to + ** request this page from the page is an SQLITE_CORRUPT error. */ + sqlite3_result_zeroblob(ctx, pCsr->szPage); + }else{ + rc = sqlite3PagerGet(pCsr->pPager, pCsr->pgno, (DbPage**)&pDbPage, 0); + if( rc==SQLITE_OK ){ + sqlite3_result_blob(ctx, sqlite3PagerGetData(pDbPage), pCsr->szPage, + SQLITE_TRANSIENT); + } + sqlite3PagerUnref(pDbPage); + } + break; + } + default: { /* schema */ + sqlite3 *db = sqlite3_context_db_handle(ctx); + sqlite3_result_text(ctx, db->aDb[pCsr->iDb].zDbSName, -1, SQLITE_STATIC); + break; + } + } + return rc; +} + +static int dbpageRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){ + DbpageCursor *pCsr = (DbpageCursor *)pCursor; + *pRowid = pCsr->pgno; + return SQLITE_OK; +} + +static int dbpageUpdate( + sqlite3_vtab *pVtab, + int argc, + sqlite3_value **argv, + sqlite_int64 *pRowid +){ + DbpageTable *pTab = (DbpageTable *)pVtab; + Pgno pgno; + DbPage *pDbPage = 0; + int rc = SQLITE_OK; + char *zErr = 0; + const char *zSchema; + int iDb; + Btree *pBt; + Pager *pPager; + int szPage; + + (void)pRowid; + if( pTab->db->flags & SQLITE_Defensive ){ + zErr = "read-only"; + goto update_fail; + } + if( argc==1 ){ + zErr = "cannot delete"; + goto update_fail; + } + pgno = sqlite3_value_int(argv[0]); + if( sqlite3_value_type(argv[0])==SQLITE_NULL + || (Pgno)sqlite3_value_int(argv[1])!=pgno + ){ + zErr = "cannot insert"; + goto update_fail; + } + zSchema = (const char*)sqlite3_value_text(argv[4]); + iDb = ALWAYS(zSchema) ? sqlite3FindDbName(pTab->db, zSchema) : -1; + if( NEVER(iDb<0) ){ + zErr = "no such schema"; + goto update_fail; + } + pBt = pTab->db->aDb[iDb].pBt; + if( NEVER(pgno<1) || NEVER(pBt==0) || NEVER(pgno>sqlite3BtreeLastPage(pBt)) ){ + zErr = "bad page number"; + goto update_fail; + } + szPage = sqlite3BtreeGetPageSize(pBt); + if( sqlite3_value_type(argv[3])!=SQLITE_BLOB + || sqlite3_value_bytes(argv[3])!=szPage + ){ + zErr = "bad page value"; + goto update_fail; + } + pPager = sqlite3BtreePager(pBt); + rc = sqlite3PagerGet(pPager, pgno, (DbPage**)&pDbPage, 0); + if( rc==SQLITE_OK ){ + const void *pData = sqlite3_value_blob(argv[3]); + assert( pData!=0 || pTab->db->mallocFailed ); + if( pData + && (rc = sqlite3PagerWrite(pDbPage))==SQLITE_OK + ){ + memcpy(sqlite3PagerGetData(pDbPage), pData, szPage); + } + } + sqlite3PagerUnref(pDbPage); + return rc; + +update_fail: + sqlite3_free(pVtab->zErrMsg); + pVtab->zErrMsg = sqlite3_mprintf("%s", zErr); + return SQLITE_ERROR; +} + +/* Since we do not know in advance which database files will be +** written by the sqlite_dbpage virtual table, start a write transaction +** on them all. +*/ +static int dbpageBegin(sqlite3_vtab *pVtab){ + DbpageTable *pTab = (DbpageTable *)pVtab; + sqlite3 *db = pTab->db; + int i; + for(i=0; i<db->nDb; i++){ + Btree *pBt = db->aDb[i].pBt; + if( pBt ) (void)sqlite3BtreeBeginTrans(pBt, 1, 0); + } + return SQLITE_OK; +} + + +/* +** Invoke this routine to register the "dbpage" virtual table module +*/ +int sqlite3DbpageRegister(sqlite3 *db){ + static sqlite3_module dbpage_module = { + 0, /* iVersion */ + dbpageConnect, /* xCreate */ + dbpageConnect, /* xConnect */ + dbpageBestIndex, /* xBestIndex */ + dbpageDisconnect, /* xDisconnect */ + dbpageDisconnect, /* xDestroy */ + dbpageOpen, /* xOpen - open a cursor */ + dbpageClose, /* xClose - close a cursor */ + dbpageFilter, /* xFilter - configure scan constraints */ + dbpageNext, /* xNext - advance a cursor */ + dbpageEof, /* xEof - check for end of scan */ + dbpageColumn, /* xColumn - read data */ + dbpageRowid, /* xRowid - read data */ + dbpageUpdate, /* xUpdate */ + dbpageBegin, /* xBegin */ + 0, /* xSync */ + 0, /* xCommit */ + 0, /* xRollback */ + 0, /* xFindMethod */ + 0, /* xRename */ + 0, /* xSavepoint */ + 0, /* xRelease */ + 0, /* xRollbackTo */ + 0, /* xShadowName */ + 0 /* xIntegrity */ + }; + return sqlite3_create_module(db, "sqlite_dbpage", &dbpage_module, 0); +} +#elif defined(SQLITE_ENABLE_DBPAGE_VTAB) +int sqlite3DbpageRegister(sqlite3 *db){ return SQLITE_OK; } +#endif /* SQLITE_ENABLE_DBSTAT_VTAB */ |