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Changes to src/pager.c.

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** 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. ** ** @(#) $Id: pager.c,v 1.47 2002/06/25 14:43:58 drh Exp $ */ #include "sqliteInt.h" #include "pager.h" #include "os.h" #include <assert.h> #include <string.h> ................................................................................ PgHdr *pNextHash, *pPrevHash; /* Hash collision chain for PgHdr.pgno */ int nRef; /* Number of users of this page */ PgHdr *pNextFree, *pPrevFree; /* Freelist of pages where nRef==0 */ PgHdr *pNextAll, *pPrevAll; /* A list of all pages */ char inJournal; /* TRUE if has been written to journal */ char inCkpt; /* TRUE if written to the checkpoint journal */ char dirty; /* TRUE if we need to write back changes */ /* SQLITE_PAGE_SIZE bytes of page data follow this header */ /* Pager.nExtra bytes of local data follow the page data */ }; /* ** Convert a pointer to a PgHdr into a pointer to its data ** and back again. ................................................................................ sqliteOsClose(&pPager->cpfd); pPager->ckptOpen = 0; } sqliteOsClose(&pPager->jfd); pPager->journalOpen = 0; sqliteOsDelete(pPager->zJournal); rc = sqliteOsReadLock(&pPager->fd); assert( rc==SQLITE_OK ); sqliteFree( pPager->aInJournal ); pPager->aInJournal = 0; for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){ pPg->inJournal = 0; pPg->dirty = 0; } pPager->state = SQLITE_READLOCK; return rc; } /* ** Read a single page from the journal file opened on file descriptor ** jfd. Playback this one page. */ ................................................................................ return rc; } pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 ); if( pPager->aInJournal==0 ){ sqliteOsReadLock(&pPager->fd); return SQLITE_NOMEM; } rc = sqliteOsOpenExclusive(pPager->zJournal, &pPager->jfd, 0); if( rc!=SQLITE_OK ){ sqliteFree(pPager->aInJournal); pPager->aInJournal = 0; sqliteOsReadLock(&pPager->fd); return SQLITE_CANTOPEN; } pPager->journalOpen = 1; ................................................................................ ** 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, together with the ** sqlitepager_dont_rollback() below, more than double the speed ** of large INSERT operations and quadruple the speed of large DELETEs. */ void sqlitepager_dont_write(Pager *pPager, Pgno pgno){ PgHdr *pPg; pPg = pager_lookup(pPager, pgno); if( pPg && pPg->dirty ){ if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){ /* If this pages is the last page in the file and the file has grown ** during the current transaction, then do NOT mark the page as clean. ** When the database file grows, we must make sure that the last page ** gets written at least once so that the disk file will be the correct ** size. If you do not write this page and the size of the file ................................................................................ ** rollback journal. */ void sqlitepager_dont_rollback(void *pData){ PgHdr *pPg = DATA_TO_PGHDR(pData); Pager *pPager = pPg->pPager; if( pPager->state!=SQLITE_WRITELOCK || pPager->journalOpen==0 ) return; if( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ){ assert( pPager->aInJournal!=0 ); pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7); pPg->inJournal = 1; if( pPager->ckptInUse ){ pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7); pPg->inCkpt = 1;

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** 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. ** ** @(#) $Id: pager.c,v 1.48 2002/07/06 16:28:48 drh Exp $ */ #include "sqliteInt.h" #include "pager.h" #include "os.h" #include <assert.h> #include <string.h> ................................................................................ PgHdr *pNextHash, *pPrevHash; /* Hash collision chain for PgHdr.pgno */ int nRef; /* Number of users of this page */ PgHdr *pNextFree, *pPrevFree; /* Freelist of pages where nRef==0 */ PgHdr *pNextAll, *pPrevAll; /* A list of all pages */ char inJournal; /* TRUE if has been written to journal */ char inCkpt; /* TRUE if written to the checkpoint journal */ char dirty; /* TRUE if we need to write back changes */ char alwaysRollback; /* Ignore dont_rollback() calls if true */ /* SQLITE_PAGE_SIZE bytes of page data follow this header */ /* Pager.nExtra bytes of local data follow the page data */ }; /* ** Convert a pointer to a PgHdr into a pointer to its data ** and back again. ................................................................................ sqliteOsClose(&pPager->cpfd); pPager->ckptOpen = 0; } sqliteOsClose(&pPager->jfd); pPager->journalOpen = 0; sqliteOsDelete(pPager->zJournal); rc = sqliteOsReadLock(&pPager->fd); sqliteFree( pPager->aInJournal ); pPager->aInJournal = 0; for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){ pPg->inJournal = 0; pPg->dirty = 0; } if( rc==SQLITE_OK ){ pPager->state = SQLITE_READLOCK; }else{ /* This can only happen if a process does a BEGIN, then forks and the ** child process does the COMMIT. Because of the semantics of unix ** file locking, the unlock will fail. */ pPager->state = SQLITE_UNLOCK; } return rc; } /* ** Read a single page from the journal file opened on file descriptor ** jfd. Playback this one page. */ ................................................................................ return rc; } pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 ); if( pPager->aInJournal==0 ){ sqliteOsReadLock(&pPager->fd); return SQLITE_NOMEM; } rc = sqliteOsOpenExclusive(pPager->zJournal, &pPager->jfd,pPager->tempFile); if( rc!=SQLITE_OK ){ sqliteFree(pPager->aInJournal); pPager->aInJournal = 0; sqliteOsReadLock(&pPager->fd); return SQLITE_CANTOPEN; } pPager->journalOpen = 1; ................................................................................ ** 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, together with the ** sqlitepager_dont_rollback() below, more than double the speed ** of large INSERT operations and quadruple the speed of large DELETEs. ** ** When this routine is called, set the alwaysRollback flag to true. ** Subsequent calls to sqlitepager_dont_rollback() for the same page ** will thereafter be ignored. This is necessary to avoid a problem ** where a page with data is added to the freelist during one part of ** a transaction then removed from the freelist during a later part ** of the same transaction and reused for some other purpose. When it ** is first added to the freelist, this routine is called. When reused, ** the dont_rollback() routine is called. But because the page contains ** critical data, we still need to be sure it gets rolled back in spite ** of the dont_rollback() call. */ void sqlitepager_dont_write(Pager *pPager, Pgno pgno){ PgHdr *pPg; pPg = pager_lookup(pPager, pgno); pPg->alwaysRollback = 1; if( pPg && pPg->dirty ){ if( pPager->dbSize==(int)pPg->pgno && pPager->origDbSize<pPager->dbSize ){ /* If this pages is the last page in the file and the file has grown ** during the current transaction, then do NOT mark the page as clean. ** When the database file grows, we must make sure that the last page ** gets written at least once so that the disk file will be the correct ** size. If you do not write this page and the size of the file ................................................................................ ** rollback journal. */ void sqlitepager_dont_rollback(void *pData){ PgHdr *pPg = DATA_TO_PGHDR(pData); Pager *pPager = pPg->pPager; if( pPager->state!=SQLITE_WRITELOCK || pPager->journalOpen==0 ) return; if( pPg->alwaysRollback ) return; if( !pPg->inJournal && (int)pPg->pgno <= pPager->origDbSize ){ assert( pPager->aInJournal!=0 ); pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7); pPg->inJournal = 1; if( pPager->ckptInUse ){ pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7); pPg->inCkpt = 1;