drh
3e7a609667
even if the user changes working directories after opening the databae. Ticket #200. (CVS 798) FossilOrigin-Name: 1c58b4fc032c5975dcce9b8ae844c0e516254a17
1686 lines
52 KiB
C
1686 lines
52 KiB
C
/*
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** 2001 September 15
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This is the implementation of the page cache subsystem or "pager".
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**
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** The pager is used to access a database disk file. It implements
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** atomic commit and rollback through the use of a journal file that
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** is separate from the database file. The pager also implements file
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** locking to prevent two processes from writing the same database
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** file simultaneously, or one process from reading the database while
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** another is writing.
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**
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** @(#) $Id: pager.c,v 1.61 2002/12/07 21:45:14 drh Exp $
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*/
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#include "os.h" /* Must be first to enable large file support */
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#include "sqliteInt.h"
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#include "pager.h"
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#include <assert.h>
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#include <string.h>
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/*
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** The page cache as a whole is always in one of the following
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** states:
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**
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** SQLITE_UNLOCK The page cache is not currently reading or
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** writing the database file. There is no
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** data held in memory. This is the initial
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** state.
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**
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** SQLITE_READLOCK The page cache is reading the database.
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** Writing is not permitted. There can be
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** multiple readers accessing the same database
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** file at the same time.
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**
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** SQLITE_WRITELOCK The page cache is writing the database.
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** Access is exclusive. No other processes or
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** threads can be reading or writing while one
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** process is writing.
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**
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** The page cache comes up in SQLITE_UNLOCK. The first time a
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** sqlite_page_get() occurs, the state transitions to SQLITE_READLOCK.
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** After all pages have been released using sqlite_page_unref(),
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** the state transitions back to SQLITE_UNLOCK. The first time
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** that sqlite_page_write() is called, the state transitions to
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** SQLITE_WRITELOCK. (Note that sqlite_page_write() can only be
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** called on an outstanding page which means that the pager must
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** be in SQLITE_READLOCK before it transitions to SQLITE_WRITELOCK.)
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** The sqlite_page_rollback() and sqlite_page_commit() functions
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** transition the state from SQLITE_WRITELOCK back to SQLITE_READLOCK.
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*/
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#define SQLITE_UNLOCK 0
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#define SQLITE_READLOCK 1
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#define SQLITE_WRITELOCK 2
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/*
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** Each in-memory image of a page begins with the following header.
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** This header is only visible to this pager module. The client
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** code that calls pager sees only the data that follows the header.
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*/
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typedef struct PgHdr PgHdr;
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struct PgHdr {
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Pager *pPager; /* The pager to which this page belongs */
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Pgno pgno; /* The page number for this page */
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PgHdr *pNextHash, *pPrevHash; /* Hash collision chain for PgHdr.pgno */
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int nRef; /* Number of users of this page */
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PgHdr *pNextFree, *pPrevFree; /* Freelist of pages where nRef==0 */
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PgHdr *pNextAll, *pPrevAll; /* A list of all pages */
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PgHdr *pNextCkpt, *pPrevCkpt; /* List of pages in the checkpoint journal */
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u8 inJournal; /* TRUE if has been written to journal */
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u8 inCkpt; /* TRUE if written to the checkpoint journal */
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u8 dirty; /* TRUE if we need to write back changes */
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u8 alwaysRollback; /* Disable dont_rollback() for this page */
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/* SQLITE_PAGE_SIZE bytes of page data follow this header */
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/* Pager.nExtra bytes of local data follow the page data */
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};
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/*
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** Convert a pointer to a PgHdr into a pointer to its data
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** and back again.
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*/
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#define PGHDR_TO_DATA(P) ((void*)(&(P)[1]))
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#define DATA_TO_PGHDR(D) (&((PgHdr*)(D))[-1])
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#define PGHDR_TO_EXTRA(P) ((void*)&((char*)(&(P)[1]))[SQLITE_PAGE_SIZE])
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/*
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** How big to make the hash table used for locating in-memory pages
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** by page number. Knuth says this should be a prime number.
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*/
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#define N_PG_HASH 2003
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/*
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** A open page cache is an instance of the following structure.
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*/
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struct Pager {
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char *zFilename; /* Name of the database file */
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char *zJournal; /* Name of the journal file */
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OsFile fd, jfd; /* File descriptors for database and journal */
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OsFile cpfd; /* File descriptor for the checkpoint journal */
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int dbSize; /* Number of pages in the file */
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int origDbSize; /* dbSize before the current change */
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int ckptSize; /* Size of database (in pages) at ckpt_begin() */
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off_t ckptJSize; /* Size of journal at ckpt_begin() */
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int nExtra; /* Add this many bytes to each in-memory page */
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void (*xDestructor)(void*); /* Call this routine when freeing pages */
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int nPage; /* Total number of in-memory pages */
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int nRef; /* Number of in-memory pages with PgHdr.nRef>0 */
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int mxPage; /* Maximum number of pages to hold in cache */
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int nHit, nMiss, nOvfl; /* Cache hits, missing, and LRU overflows */
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u8 journalOpen; /* True if journal file descriptors is valid */
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u8 useJournal; /* Do not use a rollback journal on this file */
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u8 ckptOpen; /* True if the checkpoint journal is open */
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u8 ckptInUse; /* True we are in a checkpoint */
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u8 ckptAutoopen; /* Open ckpt journal when main journal is opened*/
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u8 noSync; /* Do not sync the journal if true */
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u8 state; /* SQLITE_UNLOCK, _READLOCK or _WRITELOCK */
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u8 errMask; /* One of several kinds of errors */
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u8 tempFile; /* zFilename is a temporary file */
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u8 readOnly; /* True for a read-only database */
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u8 needSync; /* True if an fsync() is needed on the journal */
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u8 dirtyFile; /* True if database file has changed in any way */
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u8 alwaysRollback; /* Disable dont_rollback() for all pages */
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u8 journalFormat; /* Version number of the journal file */
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u8 *aInJournal; /* One bit for each page in the database file */
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u8 *aInCkpt; /* One bit for each page in the database */
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PgHdr *pFirst, *pLast; /* List of free pages */
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PgHdr *pAll; /* List of all pages */
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PgHdr *pCkpt; /* List of pages in the checkpoint journal */
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PgHdr *aHash[N_PG_HASH]; /* Hash table to map page number of PgHdr */
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};
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/*
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** These are bits that can be set in Pager.errMask.
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*/
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#define PAGER_ERR_FULL 0x01 /* a write() failed */
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#define PAGER_ERR_MEM 0x02 /* malloc() failed */
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#define PAGER_ERR_LOCK 0x04 /* error in the locking protocol */
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#define PAGER_ERR_CORRUPT 0x08 /* database or journal corruption */
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#define PAGER_ERR_DISK 0x10 /* general disk I/O error - bad hard drive? */
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/*
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** The journal file contains page records in the following
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** format.
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*/
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typedef struct PageRecord PageRecord;
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struct PageRecord {
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Pgno pgno; /* The page number */
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char aData[SQLITE_PAGE_SIZE]; /* Original data for page pgno */
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};
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/*
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** Journal files begin with the following magic string. The data
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** was obtained from /dev/random. It is used only as a sanity check.
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**
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** There are two journal formats. The older journal format writes
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** 32-bit integers in the byte-order of the host machine. The new
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** format writes integers as big-endian. All new journals use the
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** new format, but we have to be able to read an older journal in order
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** to roll it back.
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*/
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static const unsigned char aOldJournalMagic[] = {
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0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd4,
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};
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static const unsigned char aJournalMagic[] = {
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0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd5,
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};
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#define SQLITE_NEW_JOURNAL_FORMAT 1
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#define SQLITE_OLD_JOURNAL_FORMAT 0
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/*
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** The following integer, if set, causes journals to be written in the
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** old format. This is used for testing purposes only - to make sure
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** the code is able to rollback an old journal.
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*/
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#ifdef SQLITE_TEST
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int pager_old_format = 0;
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#else
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# define pager_old_format 0
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#endif
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/*
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** Hash a page number
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*/
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#define pager_hash(PN) ((PN)%N_PG_HASH)
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/*
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** Enable reference count tracking here:
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*/
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#ifdef SQLITE_TEST
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int pager_refinfo_enable = 0;
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static void pager_refinfo(PgHdr *p){
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static int cnt = 0;
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if( !pager_refinfo_enable ) return;
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printf(
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"REFCNT: %4d addr=0x%08x nRef=%d\n",
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p->pgno, (int)PGHDR_TO_DATA(p), p->nRef
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);
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cnt++; /* Something to set a breakpoint on */
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}
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# define REFINFO(X) pager_refinfo(X)
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#else
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# define REFINFO(X)
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#endif
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/*
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** Read a 32-bit integer from the given file descriptor
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*/
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static int read32bits(Pager *pPager, OsFile *fd, u32 *pRes){
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u32 res;
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int rc;
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rc = sqliteOsRead(fd, &res, sizeof(res));
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if( rc==SQLITE_OK && pPager->journalFormat==SQLITE_NEW_JOURNAL_FORMAT ){
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unsigned char ac[4];
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memcpy(ac, &res, 4);
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res = (ac[0]<<24) | (ac[1]<<16) | (ac[2]<<8) | ac[3];
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}
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*pRes = res;
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return rc;
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}
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/*
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** Write a 32-bit integer into the given file descriptor. Writing
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** is always done using the new journal format.
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*/
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static int write32bits(OsFile *fd, u32 val){
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unsigned char ac[4];
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if( pager_old_format ){
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return sqliteOsWrite(fd, &val, 4);
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}
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ac[0] = (val>>24) & 0xff;
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ac[1] = (val>>16) & 0xff;
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ac[2] = (val>>8) & 0xff;
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ac[3] = val & 0xff;
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return sqliteOsWrite(fd, ac, 4);
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}
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/*
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** Convert the bits in the pPager->errMask into an approprate
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** return code.
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*/
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static int pager_errcode(Pager *pPager){
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int rc = SQLITE_OK;
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if( pPager->errMask & PAGER_ERR_LOCK ) rc = SQLITE_PROTOCOL;
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if( pPager->errMask & PAGER_ERR_DISK ) rc = SQLITE_IOERR;
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if( pPager->errMask & PAGER_ERR_FULL ) rc = SQLITE_FULL;
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if( pPager->errMask & PAGER_ERR_MEM ) rc = SQLITE_NOMEM;
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if( pPager->errMask & PAGER_ERR_CORRUPT ) rc = SQLITE_CORRUPT;
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return rc;
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}
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/*
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** Add or remove a page from the list of all pages that are in the
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** checkpoint journal.
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**
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** The Pager keeps a separate list of pages that are currently in
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** the checkpoint journal. This helps the sqlitepager_ckpt_commit()
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** routine run MUCH faster for the common case where there are many
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** pages in memory but only a few are in the checkpoint journal.
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*/
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static void page_add_to_ckpt_list(PgHdr *pPg){
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Pager *pPager = pPg->pPager;
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if( pPg->inCkpt ) return;
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assert( pPg->pPrevCkpt==0 && pPg->pNextCkpt==0 );
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pPg->pPrevCkpt = 0;
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if( pPager->pCkpt ){
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pPager->pCkpt->pPrevCkpt = pPg;
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}
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pPg->pNextCkpt = pPager->pCkpt;
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pPager->pCkpt = pPg;
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pPg->inCkpt = 1;
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}
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static void page_remove_from_ckpt_list(PgHdr *pPg){
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if( !pPg->inCkpt ) return;
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if( pPg->pPrevCkpt ){
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assert( pPg->pPrevCkpt->pNextCkpt==pPg );
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pPg->pPrevCkpt->pNextCkpt = pPg->pNextCkpt;
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}else{
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assert( pPg->pPager->pCkpt==pPg );
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pPg->pPager->pCkpt = pPg->pNextCkpt;
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}
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if( pPg->pNextCkpt ){
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assert( pPg->pNextCkpt->pPrevCkpt==pPg );
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pPg->pNextCkpt->pPrevCkpt = pPg->pPrevCkpt;
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}
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pPg->pNextCkpt = 0;
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pPg->pPrevCkpt = 0;
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pPg->inCkpt = 0;
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}
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/*
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** Find a page in the hash table given its page number. Return
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** a pointer to the page or NULL if not found.
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*/
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static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
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PgHdr *p = pPager->aHash[pgno % N_PG_HASH];
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while( p && p->pgno!=pgno ){
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p = p->pNextHash;
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}
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return p;
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}
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/*
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** Unlock the database and clear the in-memory cache. This routine
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** sets the state of the pager back to what it was when it was first
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** opened. Any outstanding pages are invalidated and subsequent attempts
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** to access those pages will likely result in a coredump.
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*/
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static void pager_reset(Pager *pPager){
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PgHdr *pPg, *pNext;
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for(pPg=pPager->pAll; pPg; pPg=pNext){
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pNext = pPg->pNextAll;
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sqliteFree(pPg);
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}
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pPager->pFirst = 0;
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pPager->pLast = 0;
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pPager->pAll = 0;
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memset(pPager->aHash, 0, sizeof(pPager->aHash));
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pPager->nPage = 0;
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if( pPager->state>=SQLITE_WRITELOCK ){
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sqlitepager_rollback(pPager);
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}
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sqliteOsUnlock(&pPager->fd);
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pPager->state = SQLITE_UNLOCK;
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pPager->dbSize = -1;
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pPager->nRef = 0;
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assert( pPager->journalOpen==0 );
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}
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/*
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** When this routine is called, the pager has the journal file open and
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** a write lock on the database. This routine releases the database
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** write lock and acquires a read lock in its place. The journal file
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** is deleted and closed.
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*/
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static int pager_unwritelock(Pager *pPager){
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int rc;
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PgHdr *pPg;
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if( pPager->state<SQLITE_WRITELOCK ) return SQLITE_OK;
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sqlitepager_ckpt_commit(pPager);
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if( pPager->ckptOpen ){
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sqliteOsClose(&pPager->cpfd);
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pPager->ckptOpen = 0;
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}
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if( pPager->journalOpen ){
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sqliteOsClose(&pPager->jfd);
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pPager->journalOpen = 0;
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sqliteOsDelete(pPager->zJournal);
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sqliteFree( pPager->aInJournal );
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pPager->aInJournal = 0;
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for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
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pPg->inJournal = 0;
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pPg->dirty = 0;
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}
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}else{
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assert( pPager->dirtyFile==0 || pPager->useJournal==0 );
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}
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rc = sqliteOsReadLock(&pPager->fd);
|
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if( rc==SQLITE_OK ){
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pPager->state = SQLITE_READLOCK;
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}else{
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/* This can only happen if a process does a BEGIN, then forks and the
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** child process does the COMMIT. Because of the semantics of unix
|
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** file locking, the unlock will fail.
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*/
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pPager->state = SQLITE_UNLOCK;
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}
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return rc;
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}
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|
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/*
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** Read a single page from the journal file opened on file descriptor
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** jfd. Playback this one page.
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*/
|
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static int pager_playback_one_page(Pager *pPager, OsFile *jfd){
|
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int rc;
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PgHdr *pPg; /* An existing page in the cache */
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PageRecord pgRec;
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rc = read32bits(pPager, jfd, &pgRec.pgno);
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if( rc!=SQLITE_OK ) return rc;
|
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rc = sqliteOsRead(jfd, &pgRec.aData, sizeof(pgRec.aData));
|
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if( rc!=SQLITE_OK ) return rc;
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|
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/* Sanity checking on the page */
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if( pgRec.pgno>pPager->dbSize || pgRec.pgno==0 ) return SQLITE_CORRUPT;
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|
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/* Playback the page. Update the in-memory copy of the page
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** at the same time, if there is one.
|
|
*/
|
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pPg = pager_lookup(pPager, pgRec.pgno);
|
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if( pPg ){
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memcpy(PGHDR_TO_DATA(pPg), pgRec.aData, SQLITE_PAGE_SIZE);
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memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
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}
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rc = sqliteOsSeek(&pPager->fd, (pgRec.pgno-1)*(off_t)SQLITE_PAGE_SIZE);
|
|
if( rc==SQLITE_OK ){
|
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rc = sqliteOsWrite(&pPager->fd, pgRec.aData, SQLITE_PAGE_SIZE);
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|
}
|
|
return rc;
|
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}
|
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|
|
/*
|
|
** 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: There is an initial
|
|
** file-type string for sanity checking. Then there is a single
|
|
** Pgno number which is the number of pages in the database before
|
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** changes were made. The database is truncated to this size.
|
|
** Next come zero or more page records where each page record
|
|
** consists of a Pgno and SQLITE_PAGE_SIZE bytes of data. See
|
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** the PageRecord structure for details.
|
|
**
|
|
** If the file opened as the journal file is not a well-formed
|
|
** journal file (as determined by looking at the magic number
|
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** at the beginning) then this routine returns SQLITE_PROTOCOL.
|
|
** If any other errors occur during playback, the database will
|
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** likely be corrupted, so the PAGER_ERR_CORRUPT bit is set in
|
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** pPager->errMask and SQLITE_CORRUPT is returned. If it all
|
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** works, then this routine returns SQLITE_OK.
|
|
*/
|
|
static int pager_playback(Pager *pPager){
|
|
off_t nRec; /* Number of Records */
|
|
int i; /* Loop counter */
|
|
Pgno mxPg = 0; /* Size of the original file in pages */
|
|
unsigned char aMagic[sizeof(aJournalMagic)];
|
|
int rc;
|
|
|
|
/* Figure out how many records are in the journal. Abort early if
|
|
** the journal is empty.
|
|
*/
|
|
assert( pPager->journalOpen );
|
|
sqliteOsSeek(&pPager->jfd, 0);
|
|
rc = sqliteOsFileSize(&pPager->jfd, &nRec);
|
|
if( rc!=SQLITE_OK ){
|
|
goto end_playback;
|
|
}
|
|
if( nRec <= sizeof(aMagic)+sizeof(Pgno) ){
|
|
goto end_playback;
|
|
}
|
|
nRec = (nRec - (sizeof(aMagic)+sizeof(Pgno))) / sizeof(PageRecord);
|
|
|
|
/* Read the beginning of the journal and truncate the
|
|
** database file back to its original size.
|
|
*/
|
|
rc = sqliteOsRead(&pPager->jfd, aMagic, sizeof(aMagic));
|
|
if( rc!=SQLITE_OK ){
|
|
rc = SQLITE_PROTOCOL;
|
|
goto end_playback;
|
|
}
|
|
if( memcmp(aMagic, aOldJournalMagic, sizeof(aMagic))==0 ){
|
|
pPager->journalFormat = SQLITE_OLD_JOURNAL_FORMAT;
|
|
}else if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))==0 ){
|
|
pPager->journalFormat = SQLITE_NEW_JOURNAL_FORMAT;
|
|
}else{
|
|
rc = SQLITE_PROTOCOL;
|
|
goto end_playback;
|
|
}
|
|
rc = read32bits(pPager, &pPager->jfd, &mxPg);
|
|
if( rc!=SQLITE_OK ){
|
|
goto end_playback;
|
|
}
|
|
rc = sqliteOsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)mxPg);
|
|
if( rc!=SQLITE_OK ){
|
|
goto end_playback;
|
|
}
|
|
pPager->dbSize = mxPg;
|
|
|
|
/* Copy original pages out of the journal and back into the database file.
|
|
*/
|
|
for(i=nRec-1; i>=0; i--){
|
|
rc = pager_playback_one_page(pPager, &pPager->jfd);
|
|
if( rc!=SQLITE_OK ) break;
|
|
}
|
|
|
|
end_playback:
|
|
if( rc!=SQLITE_OK ){
|
|
pager_unwritelock(pPager);
|
|
pPager->errMask |= PAGER_ERR_CORRUPT;
|
|
rc = SQLITE_CORRUPT;
|
|
}else{
|
|
rc = pager_unwritelock(pPager);
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Playback the checkpoint journal.
|
|
**
|
|
** This is similar to playing back the transaction journal but with
|
|
** a few extra twists.
|
|
**
|
|
** (1) The number of pages in the database file at the start of
|
|
** the checkpoint is stored in pPager->ckptSize, not in the
|
|
** journal file itself.
|
|
**
|
|
** (2) In addition to playing back the checkpoint journal, also
|
|
** playback all pages of the transaction journal beginning
|
|
** at offset pPager->ckptJSize.
|
|
*/
|
|
static int pager_ckpt_playback(Pager *pPager){
|
|
off_t nRec; /* Number of Records */
|
|
int i; /* Loop counter */
|
|
int rc;
|
|
|
|
/* Truncate the database back to its original size.
|
|
*/
|
|
rc = sqliteOsTruncate(&pPager->fd, SQLITE_PAGE_SIZE*(off_t)pPager->ckptSize);
|
|
pPager->dbSize = pPager->ckptSize;
|
|
|
|
/* Figure out how many records are in the checkpoint journal.
|
|
*/
|
|
assert( pPager->ckptInUse && pPager->journalOpen );
|
|
sqliteOsSeek(&pPager->cpfd, 0);
|
|
rc = sqliteOsFileSize(&pPager->cpfd, &nRec);
|
|
if( rc!=SQLITE_OK ){
|
|
goto end_ckpt_playback;
|
|
}
|
|
nRec /= sizeof(PageRecord);
|
|
|
|
/* Copy original pages out of the checkpoint journal and back into the
|
|
** database file.
|
|
*/
|
|
if( pager_old_format ){
|
|
pPager->journalFormat = SQLITE_OLD_JOURNAL_FORMAT;
|
|
}else{
|
|
pPager->journalFormat = SQLITE_NEW_JOURNAL_FORMAT;
|
|
}
|
|
for(i=nRec-1; i>=0; i--){
|
|
rc = pager_playback_one_page(pPager, &pPager->cpfd);
|
|
if( rc!=SQLITE_OK ) goto end_ckpt_playback;
|
|
}
|
|
|
|
/* Figure out how many pages need to be copied out of the transaction
|
|
** journal.
|
|
*/
|
|
rc = sqliteOsSeek(&pPager->jfd, pPager->ckptJSize);
|
|
if( rc!=SQLITE_OK ){
|
|
goto end_ckpt_playback;
|
|
}
|
|
rc = sqliteOsFileSize(&pPager->jfd, &nRec);
|
|
if( rc!=SQLITE_OK ){
|
|
goto end_ckpt_playback;
|
|
}
|
|
nRec = (nRec - pPager->ckptJSize)/sizeof(PageRecord);
|
|
for(i=nRec-1; i>=0; i--){
|
|
rc = pager_playback_one_page(pPager, &pPager->jfd);
|
|
if( rc!=SQLITE_OK ) goto end_ckpt_playback;
|
|
}
|
|
|
|
|
|
end_ckpt_playback:
|
|
if( rc!=SQLITE_OK ){
|
|
pPager->errMask |= PAGER_ERR_CORRUPT;
|
|
rc = SQLITE_CORRUPT;
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Change the maximum number of in-memory pages that are allowed.
|
|
**
|
|
** The maximum number is the absolute value of the mxPage parameter.
|
|
** If mxPage is negative, the noSync flag is also set. noSync bypasses
|
|
** calls to sqliteOsSync(). The pager runs much faster with noSync on,
|
|
** but if the operating system crashes or there is an abrupt power
|
|
** failure, the database file might be left in an inconsistent and
|
|
** unrepairable state.
|
|
*/
|
|
void sqlitepager_set_cachesize(Pager *pPager, int mxPage){
|
|
if( mxPage>=0 ){
|
|
pPager->noSync = pPager->tempFile;
|
|
}else{
|
|
pPager->noSync = 1;
|
|
mxPage = -mxPage;
|
|
}
|
|
if( mxPage>10 ){
|
|
pPager->mxPage = mxPage;
|
|
}
|
|
}
|
|
|
|
/*
|
|
** Open a temporary file. Write the name of the file into zName
|
|
** (zName must be at least SQLITE_TEMPNAME_SIZE bytes long.) Write
|
|
** the file descriptor into *fd. 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.
|
|
*/
|
|
static int sqlitepager_opentemp(char *zFile, OsFile *fd){
|
|
int cnt = 8;
|
|
int rc;
|
|
do{
|
|
cnt--;
|
|
sqliteOsTempFileName(zFile);
|
|
rc = sqliteOsOpenExclusive(zFile, fd, 1);
|
|
}while( cnt>0 && rc!=SQLITE_OK );
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Create a new page cache and put a pointer to the page cache in *ppPager.
|
|
** The file to be cached need not exist. The file is not locked until
|
|
** the first call to sqlitepager_get() and is only held open until the
|
|
** last page is released using sqlitepager_unref().
|
|
**
|
|
** If zFilename is NULL then a randomly-named temporary file is created
|
|
** and used as the file to be cached. The file will be deleted
|
|
** automatically when it is closed.
|
|
*/
|
|
int sqlitepager_open(
|
|
Pager **ppPager, /* Return the Pager structure here */
|
|
const char *zFilename, /* Name of the database file to open */
|
|
int mxPage, /* Max number of in-memory cache pages */
|
|
int nExtra, /* Extra bytes append to each in-memory page */
|
|
int useJournal /* TRUE to use a rollback journal on this file */
|
|
){
|
|
Pager *pPager;
|
|
char *zFullPathname;
|
|
int nameLen;
|
|
OsFile fd;
|
|
int rc;
|
|
int tempFile;
|
|
int readOnly = 0;
|
|
char zTemp[SQLITE_TEMPNAME_SIZE];
|
|
|
|
*ppPager = 0;
|
|
if( sqlite_malloc_failed ){
|
|
return SQLITE_NOMEM;
|
|
}
|
|
if( zFilename ){
|
|
zFullPathname = sqliteOsFullPathname(zFilename);
|
|
rc = sqliteOsOpenReadWrite(zFullPathname, &fd, &readOnly);
|
|
tempFile = 0;
|
|
}else{
|
|
rc = sqlitepager_opentemp(zTemp, &fd);
|
|
zFilename = zTemp;
|
|
zFullPathname = sqliteOsFullPathname(zFilename);
|
|
tempFile = 1;
|
|
}
|
|
if( sqlite_malloc_failed ){
|
|
return SQLITE_NOMEM;
|
|
}
|
|
if( rc!=SQLITE_OK ){
|
|
sqliteFree(zFullPathname);
|
|
return SQLITE_CANTOPEN;
|
|
}
|
|
nameLen = strlen(zFullPathname);
|
|
pPager = sqliteMalloc( sizeof(*pPager) + nameLen*2 + 30 );
|
|
if( pPager==0 ){
|
|
sqliteOsClose(&fd);
|
|
sqliteFree(zFullPathname);
|
|
return SQLITE_NOMEM;
|
|
}
|
|
pPager->zFilename = (char*)&pPager[1];
|
|
pPager->zJournal = &pPager->zFilename[nameLen+1];
|
|
strcpy(pPager->zFilename, zFullPathname);
|
|
strcpy(pPager->zJournal, zFullPathname);
|
|
sqliteFree(zFullPathname);
|
|
strcpy(&pPager->zJournal[nameLen], "-journal");
|
|
pPager->fd = fd;
|
|
pPager->journalOpen = 0;
|
|
pPager->useJournal = useJournal;
|
|
pPager->ckptOpen = 0;
|
|
pPager->ckptInUse = 0;
|
|
pPager->nRef = 0;
|
|
pPager->dbSize = -1;
|
|
pPager->ckptSize = 0;
|
|
pPager->ckptJSize = 0;
|
|
pPager->nPage = 0;
|
|
pPager->mxPage = mxPage>5 ? mxPage : 10;
|
|
pPager->state = SQLITE_UNLOCK;
|
|
pPager->errMask = 0;
|
|
pPager->tempFile = tempFile;
|
|
pPager->readOnly = readOnly;
|
|
pPager->needSync = 0;
|
|
pPager->noSync = pPager->tempFile || !useJournal;
|
|
pPager->pFirst = 0;
|
|
pPager->pLast = 0;
|
|
pPager->nExtra = nExtra;
|
|
memset(pPager->aHash, 0, sizeof(pPager->aHash));
|
|
*ppPager = pPager;
|
|
return SQLITE_OK;
|
|
}
|
|
|
|
/*
|
|
** Set the destructor for this pager. If not NULL, the destructor is called
|
|
** when the reference count on each page reaches zero. The destructor can
|
|
** be used to clean up information in the extra segment appended to each page.
|
|
**
|
|
** The destructor is not called as a result sqlitepager_close().
|
|
** Destructors are only called by sqlitepager_unref().
|
|
*/
|
|
void sqlitepager_set_destructor(Pager *pPager, void (*xDesc)(void*)){
|
|
pPager->xDestructor = xDesc;
|
|
}
|
|
|
|
/*
|
|
** Return the total number of pages in the disk file associated with
|
|
** pPager.
|
|
*/
|
|
int sqlitepager_pagecount(Pager *pPager){
|
|
off_t n;
|
|
assert( pPager!=0 );
|
|
if( pPager->dbSize>=0 ){
|
|
return pPager->dbSize;
|
|
}
|
|
if( sqliteOsFileSize(&pPager->fd, &n)!=SQLITE_OK ){
|
|
pPager->errMask |= PAGER_ERR_DISK;
|
|
return 0;
|
|
}
|
|
n /= SQLITE_PAGE_SIZE;
|
|
if( pPager->state!=SQLITE_UNLOCK ){
|
|
pPager->dbSize = n;
|
|
}
|
|
return n;
|
|
}
|
|
|
|
/*
|
|
** 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.
|
|
*/
|
|
int sqlitepager_close(Pager *pPager){
|
|
PgHdr *pPg, *pNext;
|
|
switch( pPager->state ){
|
|
case SQLITE_WRITELOCK: {
|
|
sqlitepager_rollback(pPager);
|
|
sqliteOsUnlock(&pPager->fd);
|
|
assert( pPager->journalOpen==0 );
|
|
break;
|
|
}
|
|
case SQLITE_READLOCK: {
|
|
sqliteOsUnlock(&pPager->fd);
|
|
break;
|
|
}
|
|
default: {
|
|
/* Do nothing */
|
|
break;
|
|
}
|
|
}
|
|
for(pPg=pPager->pAll; pPg; pPg=pNext){
|
|
pNext = pPg->pNextAll;
|
|
sqliteFree(pPg);
|
|
}
|
|
sqliteOsClose(&pPager->fd);
|
|
assert( pPager->journalOpen==0 );
|
|
/* Temp files are automatically deleted by the OS
|
|
** if( pPager->tempFile ){
|
|
** sqliteOsDelete(pPager->zFilename);
|
|
** }
|
|
*/
|
|
sqliteFree(pPager);
|
|
return SQLITE_OK;
|
|
}
|
|
|
|
/*
|
|
** Return the page number for the given page data.
|
|
*/
|
|
Pgno sqlitepager_pagenumber(void *pData){
|
|
PgHdr *p = DATA_TO_PGHDR(pData);
|
|
return p->pgno;
|
|
}
|
|
|
|
/*
|
|
** Increment the reference count for a page. If the page is
|
|
** currently on the freelist (the reference count is zero) then
|
|
** remove it from the freelist.
|
|
*/
|
|
static void page_ref(PgHdr *pPg){
|
|
if( pPg->nRef==0 ){
|
|
/* The page is currently on the freelist. Remove it. */
|
|
if( pPg->pPrevFree ){
|
|
pPg->pPrevFree->pNextFree = pPg->pNextFree;
|
|
}else{
|
|
pPg->pPager->pFirst = pPg->pNextFree;
|
|
}
|
|
if( pPg->pNextFree ){
|
|
pPg->pNextFree->pPrevFree = pPg->pPrevFree;
|
|
}else{
|
|
pPg->pPager->pLast = pPg->pPrevFree;
|
|
}
|
|
pPg->pPager->nRef++;
|
|
}
|
|
pPg->nRef++;
|
|
REFINFO(pPg);
|
|
}
|
|
|
|
/*
|
|
** Increment the reference count for a page. The input pointer is
|
|
** a reference to the page data.
|
|
*/
|
|
int sqlitepager_ref(void *pData){
|
|
PgHdr *pPg = DATA_TO_PGHDR(pData);
|
|
page_ref(pPg);
|
|
return SQLITE_OK;
|
|
}
|
|
|
|
/*
|
|
** Sync the journal and then write all free dirty pages to the database
|
|
** file.
|
|
**
|
|
** Writing all free dirty pages to the database after the sync is a
|
|
** non-obvious optimization. fsync() is an expensive operation so we
|
|
** want to minimize the number ot times it is called. After an fsync() call,
|
|
** we are free to write dirty pages back to the database. It is best
|
|
** to go ahead and write as many dirty pages as possible to minimize
|
|
** the risk of having to do another fsync() later on. Writing dirty
|
|
** free pages in this way was observed to make database operations go
|
|
** up to 10 times faster.
|
|
**
|
|
** If we are writing to temporary database, there is no need to preserve
|
|
** the integrity of the journal file, so we can save time and skip the
|
|
** fsync().
|
|
*/
|
|
static int syncAllPages(Pager *pPager){
|
|
PgHdr *pPg;
|
|
Pgno lastPgno;
|
|
int rc = SQLITE_OK;
|
|
|
|
/* Sync the journal before modifying the main database
|
|
** (assuming there is a journal and it needs to be synced.)
|
|
*/
|
|
if( pPager->needSync ){
|
|
if( !pPager->tempFile ){
|
|
rc = sqliteOsSync(&pPager->jfd);
|
|
if( rc!=0 ) return rc;
|
|
}
|
|
pPager->needSync = 0;
|
|
}
|
|
|
|
/* Write all dirty free pages to the disk in the order that they
|
|
** appear on the disk. We have experimented with sorting the pages
|
|
** by page numbers so that they are written in order, but that does
|
|
** not appear to improve performance.
|
|
*/
|
|
for(pPg=pPager->pFirst; pPg; pPg=pPg->pNextFree){
|
|
if( pPg->dirty ){
|
|
if( lastPgno==0 || pPg->pgno!=lastPgno+1 ){
|
|
sqliteOsSeek(&pPager->fd, (pPg->pgno-1)*(off_t)SQLITE_PAGE_SIZE);
|
|
}
|
|
rc = sqliteOsWrite(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
|
|
if( rc!=SQLITE_OK ) break;
|
|
pPg->dirty = 0;
|
|
lastPgno = pPg->pgno;
|
|
}
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Acquire a page.
|
|
**
|
|
** A read lock on the disk file is obtained when the first page is acquired.
|
|
** This read lock is dropped when the last page is released.
|
|
**
|
|
** A _get works for any page number greater than 0. If the database
|
|
** file is smaller than the requested page, then no actual disk
|
|
** read occurs and the memory image of the page is initialized to
|
|
** all zeros. The extra data appended to a page is always initialized
|
|
** to zeros the first time a page is loaded into memory.
|
|
**
|
|
** The acquisition might fail for several reasons. In all cases,
|
|
** an appropriate error code is returned and *ppPage is set to NULL.
|
|
**
|
|
** See also sqlitepager_lookup(). 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.
|
|
*/
|
|
int sqlitepager_get(Pager *pPager, Pgno pgno, void **ppPage){
|
|
PgHdr *pPg;
|
|
int rc;
|
|
|
|
/* Make sure we have not hit any critical errors.
|
|
*/
|
|
if( pPager==0 || pgno==0 ){
|
|
return SQLITE_ERROR;
|
|
}
|
|
if( pPager->errMask & ~(PAGER_ERR_FULL) ){
|
|
return pager_errcode(pPager);
|
|
}
|
|
|
|
/* If this is the first page accessed, then get a read lock
|
|
** on the database file.
|
|
*/
|
|
if( pPager->nRef==0 ){
|
|
rc = sqliteOsReadLock(&pPager->fd);
|
|
if( rc!=SQLITE_OK ){
|
|
*ppPage = 0;
|
|
return rc;
|
|
}
|
|
pPager->state = SQLITE_READLOCK;
|
|
|
|
/* If a journal file exists, try to play it back.
|
|
*/
|
|
if( pPager->useJournal && sqliteOsFileExists(pPager->zJournal) ){
|
|
int rc, dummy;
|
|
|
|
/* Get a write lock on the database
|
|
*/
|
|
rc = sqliteOsWriteLock(&pPager->fd);
|
|
if( rc!=SQLITE_OK ){
|
|
if( sqliteOsUnlock(&pPager->fd)!=SQLITE_OK ){
|
|
/* This should never happen! */
|
|
rc = SQLITE_INTERNAL;
|
|
}
|
|
*ppPage = 0;
|
|
return rc;
|
|
}
|
|
pPager->state = SQLITE_WRITELOCK;
|
|
|
|
/* Open the journal for exclusive access. Return SQLITE_BUSY if
|
|
** we cannot get exclusive access to the journal file.
|
|
**
|
|
** Even though we will only be reading from the journal, not writing,
|
|
** we have to open the journal for writing in order to obtain an
|
|
** exclusive access lock.
|
|
*/
|
|
rc = sqliteOsOpenReadWrite(pPager->zJournal, &pPager->jfd, &dummy);
|
|
if( rc!=SQLITE_OK ){
|
|
rc = sqliteOsUnlock(&pPager->fd);
|
|
assert( rc==SQLITE_OK );
|
|
*ppPage = 0;
|
|
return SQLITE_BUSY;
|
|
}
|
|
pPager->journalOpen = 1;
|
|
|
|
/* Playback and delete the journal. Drop the database write
|
|
** lock and reacquire the read lock.
|
|
*/
|
|
rc = pager_playback(pPager);
|
|
if( rc!=SQLITE_OK ){
|
|
return rc;
|
|
}
|
|
}
|
|
pPg = 0;
|
|
}else{
|
|
/* Search for page in cache */
|
|
pPg = pager_lookup(pPager, pgno);
|
|
}
|
|
if( pPg==0 ){
|
|
/* The requested page is not in the page cache. */
|
|
int h;
|
|
pPager->nMiss++;
|
|
if( pPager->nPage<pPager->mxPage || pPager->pFirst==0 ){
|
|
/* Create a new page */
|
|
pPg = sqliteMalloc( sizeof(*pPg) + SQLITE_PAGE_SIZE + pPager->nExtra );
|
|
if( pPg==0 ){
|
|
*ppPage = 0;
|
|
pager_unwritelock(pPager);
|
|
pPager->errMask |= PAGER_ERR_MEM;
|
|
return SQLITE_NOMEM;
|
|
}
|
|
pPg->pPager = pPager;
|
|
pPg->pNextAll = pPager->pAll;
|
|
if( pPager->pAll ){
|
|
pPager->pAll->pPrevAll = pPg;
|
|
}
|
|
pPg->pPrevAll = 0;
|
|
pPager->pAll = pPg;
|
|
pPager->nPage++;
|
|
}else{
|
|
/* Recycle an older page. First locate the page to be recycled.
|
|
** Try to find one that is not dirty and is near the head of
|
|
** of the free list */
|
|
pPg = pPager->pFirst;
|
|
while( pPg && pPg->dirty ){
|
|
pPg = pPg->pNextFree;
|
|
}
|
|
|
|
/* If we could not find a page that has not been used recently
|
|
** and which is not dirty, then sync the journal and write all
|
|
** dirty free pages into the database file, thus making them
|
|
** clean pages and available for recycling.
|
|
**
|
|
** We have to sync the journal before writing a page to the main
|
|
** database. But syncing is a very slow operation. So after a
|
|
** sync, it is best to write everything we can back to the main
|
|
** database to minimize the risk of having to sync again in the
|
|
** near future. That is why we write all dirty pages after a
|
|
** sync.
|
|
*/
|
|
if( pPg==0 ){
|
|
int rc = syncAllPages(pPager);
|
|
if( rc!=0 ){
|
|
sqlitepager_rollback(pPager);
|
|
*ppPage = 0;
|
|
return SQLITE_IOERR;
|
|
}
|
|
pPg = pPager->pFirst;
|
|
}
|
|
assert( pPg->nRef==0 );
|
|
assert( pPg->dirty==0 );
|
|
|
|
/* If the page we are recyclying is marked as alwaysRollback, then
|
|
** set the global alwaysRollback flag, thus disabling the
|
|
** sqlite_dont_rollback() optimization for the rest of this transaction.
|
|
** It is necessary to do this because the page marked alwaysRollback
|
|
** might be reloaded at a later time but at that point we won't remember
|
|
** that is was marked alwaysRollback. This means that all pages must
|
|
** be marked as alwaysRollback from here on out.
|
|
*/
|
|
if( pPg->alwaysRollback ){
|
|
pPager->alwaysRollback = 1;
|
|
}
|
|
|
|
/* Unlink the old page from the free list and the hash table
|
|
*/
|
|
if( pPg->pPrevFree ){
|
|
pPg->pPrevFree->pNextFree = pPg->pNextFree;
|
|
}else{
|
|
assert( pPager->pFirst==pPg );
|
|
pPager->pFirst = pPg->pNextFree;
|
|
}
|
|
if( pPg->pNextFree ){
|
|
pPg->pNextFree->pPrevFree = pPg->pPrevFree;
|
|
}else{
|
|
assert( pPager->pLast==pPg );
|
|
pPager->pLast = pPg->pPrevFree;
|
|
}
|
|
pPg->pNextFree = pPg->pPrevFree = 0;
|
|
if( pPg->pNextHash ){
|
|
pPg->pNextHash->pPrevHash = pPg->pPrevHash;
|
|
}
|
|
if( pPg->pPrevHash ){
|
|
pPg->pPrevHash->pNextHash = pPg->pNextHash;
|
|
}else{
|
|
h = pager_hash(pPg->pgno);
|
|
assert( pPager->aHash[h]==pPg );
|
|
pPager->aHash[h] = pPg->pNextHash;
|
|
}
|
|
pPg->pNextHash = pPg->pPrevHash = 0;
|
|
pPager->nOvfl++;
|
|
}
|
|
pPg->pgno = pgno;
|
|
if( pPager->aInJournal && (int)pgno<=pPager->origDbSize ){
|
|
pPg->inJournal = (pPager->aInJournal[pgno/8] & (1<<(pgno&7)))!=0;
|
|
}else{
|
|
pPg->inJournal = 0;
|
|
}
|
|
if( pPager->aInCkpt && (int)pgno<=pPager->ckptSize
|
|
&& (pPager->aInCkpt[pgno/8] & (1<<(pgno&7)))!=0 ){
|
|
page_add_to_ckpt_list(pPg);
|
|
}else{
|
|
page_remove_from_ckpt_list(pPg);
|
|
}
|
|
pPg->dirty = 0;
|
|
pPg->nRef = 1;
|
|
REFINFO(pPg);
|
|
pPager->nRef++;
|
|
h = pager_hash(pgno);
|
|
pPg->pNextHash = pPager->aHash[h];
|
|
pPager->aHash[h] = pPg;
|
|
if( pPg->pNextHash ){
|
|
assert( pPg->pNextHash->pPrevHash==0 );
|
|
pPg->pNextHash->pPrevHash = pPg;
|
|
}
|
|
if( pPager->dbSize<0 ) sqlitepager_pagecount(pPager);
|
|
if( pPager->dbSize<(int)pgno ){
|
|
memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
|
|
}else{
|
|
int rc;
|
|
sqliteOsSeek(&pPager->fd, (pgno-1)*(off_t)SQLITE_PAGE_SIZE);
|
|
rc = sqliteOsRead(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
|
|
if( rc!=SQLITE_OK ){
|
|
off_t fileSize;
|
|
if( sqliteOsFileSize(&pPager->fd,&fileSize)!=SQLITE_OK
|
|
|| fileSize>=pgno*SQLITE_PAGE_SIZE ){
|
|
return rc;
|
|
}else{
|
|
memset(PGHDR_TO_DATA(pPg), 0, SQLITE_PAGE_SIZE);
|
|
}
|
|
}
|
|
}
|
|
if( pPager->nExtra>0 ){
|
|
memset(PGHDR_TO_EXTRA(pPg), 0, pPager->nExtra);
|
|
}
|
|
}else{
|
|
/* The requested page is in the page cache. */
|
|
pPager->nHit++;
|
|
page_ref(pPg);
|
|
}
|
|
*ppPage = PGHDR_TO_DATA(pPg);
|
|
return SQLITE_OK;
|
|
}
|
|
|
|
/*
|
|
** 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 sqlitepager_get(). The difference between this routine
|
|
** and sqlitepager_get() 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.
|
|
*/
|
|
void *sqlitepager_lookup(Pager *pPager, Pgno pgno){
|
|
PgHdr *pPg;
|
|
|
|
/* Make sure we have not hit any critical errors.
|
|
*/
|
|
if( pPager==0 || pgno==0 ){
|
|
return 0;
|
|
}
|
|
if( pPager->errMask & ~(PAGER_ERR_FULL) ){
|
|
return 0;
|
|
}
|
|
if( pPager->nRef==0 ){
|
|
return 0;
|
|
}
|
|
pPg = pager_lookup(pPager, pgno);
|
|
if( pPg==0 ) return 0;
|
|
page_ref(pPg);
|
|
return PGHDR_TO_DATA(pPg);
|
|
}
|
|
|
|
/*
|
|
** Release a page.
|
|
**
|
|
** If the number of references to the page drop to zero, then the
|
|
** page is added to the LRU list. When all references to all pages
|
|
** are released, a rollback occurs and the lock on the database is
|
|
** removed.
|
|
*/
|
|
int sqlitepager_unref(void *pData){
|
|
PgHdr *pPg;
|
|
|
|
/* Decrement the reference count for this page
|
|
*/
|
|
pPg = DATA_TO_PGHDR(pData);
|
|
assert( pPg->nRef>0 );
|
|
pPg->nRef--;
|
|
REFINFO(pPg);
|
|
|
|
/* When the number of references to a page reach 0, call the
|
|
** destructor and add the page to the freelist.
|
|
*/
|
|
if( pPg->nRef==0 ){
|
|
Pager *pPager;
|
|
pPager = pPg->pPager;
|
|
pPg->pNextFree = 0;
|
|
pPg->pPrevFree = pPager->pLast;
|
|
pPager->pLast = pPg;
|
|
if( pPg->pPrevFree ){
|
|
pPg->pPrevFree->pNextFree = pPg;
|
|
}else{
|
|
pPager->pFirst = pPg;
|
|
}
|
|
if( pPager->xDestructor ){
|
|
pPager->xDestructor(pData);
|
|
}
|
|
|
|
/* When all pages reach the freelist, drop the read lock from
|
|
** the database file.
|
|
*/
|
|
pPager->nRef--;
|
|
assert( pPager->nRef>=0 );
|
|
if( pPager->nRef==0 ){
|
|
pager_reset(pPager);
|
|
}
|
|
}
|
|
return SQLITE_OK;
|
|
}
|
|
|
|
/*
|
|
** Create a journal file for pPager. There should already be a write
|
|
** lock on the database file when this routine is called.
|
|
**
|
|
** Return SQLITE_OK if everything. Return an error code and release the
|
|
** write lock if anything goes wrong.
|
|
*/
|
|
static int pager_open_journal(Pager *pPager){
|
|
int rc;
|
|
assert( pPager->state==SQLITE_WRITELOCK );
|
|
assert( pPager->journalOpen==0 );
|
|
assert( pPager->useJournal );
|
|
pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
|
|
if( pPager->aInJournal==0 ){
|
|
sqliteOsReadLock(&pPager->fd);
|
|
pPager->state = SQLITE_READLOCK;
|
|
return SQLITE_NOMEM;
|
|
}
|
|
rc = sqliteOsOpenExclusive(pPager->zJournal, &pPager->jfd,pPager->tempFile);
|
|
if( rc!=SQLITE_OK ){
|
|
sqliteFree(pPager->aInJournal);
|
|
pPager->aInJournal = 0;
|
|
sqliteOsReadLock(&pPager->fd);
|
|
pPager->state = SQLITE_READLOCK;
|
|
return SQLITE_CANTOPEN;
|
|
}
|
|
pPager->journalOpen = 1;
|
|
pPager->needSync = 0;
|
|
pPager->alwaysRollback = 0;
|
|
sqlitepager_pagecount(pPager);
|
|
pPager->origDbSize = pPager->dbSize;
|
|
if( pager_old_format ){
|
|
rc = sqliteOsWrite(&pPager->jfd, aOldJournalMagic,
|
|
sizeof(aOldJournalMagic));
|
|
}else{
|
|
rc = sqliteOsWrite(&pPager->jfd, aJournalMagic, sizeof(aJournalMagic));
|
|
}
|
|
if( rc==SQLITE_OK ){
|
|
rc = write32bits(&pPager->jfd, pPager->dbSize);
|
|
}
|
|
if( pPager->ckptAutoopen && rc==SQLITE_OK ){
|
|
rc = sqlitepager_ckpt_begin(pPager);
|
|
}
|
|
if( rc!=SQLITE_OK ){
|
|
rc = pager_unwritelock(pPager);
|
|
if( rc==SQLITE_OK ){
|
|
rc = SQLITE_FULL;
|
|
}
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Acquire a write-lock on the database. The lock is removed when
|
|
** the any of the following happen:
|
|
**
|
|
** * sqlitepager_commit() is called.
|
|
** * sqlitepager_rollback() is called.
|
|
** * sqlitepager_close() is called.
|
|
** * sqlitepager_unref() is called to on every outstanding page.
|
|
**
|
|
** The parameter to this routine is a pointer to any open page of the
|
|
** database file. Nothing changes about the page - it is used merely
|
|
** to acquire a pointer to the Pager structure and as proof that there
|
|
** is already a read-lock on the database.
|
|
**
|
|
** A journal file is opened if this is not a temporary file. For
|
|
** temporary files, the opening of the journal file is deferred until
|
|
** there is an actual need to write to the journal.
|
|
**
|
|
** If the database is already write-locked, this routine is a no-op.
|
|
*/
|
|
int sqlitepager_begin(void *pData){
|
|
PgHdr *pPg = DATA_TO_PGHDR(pData);
|
|
Pager *pPager = pPg->pPager;
|
|
int rc = SQLITE_OK;
|
|
assert( pPg->nRef>0 );
|
|
assert( pPager->state!=SQLITE_UNLOCK );
|
|
if( pPager->state==SQLITE_READLOCK ){
|
|
assert( pPager->aInJournal==0 );
|
|
rc = sqliteOsWriteLock(&pPager->fd);
|
|
if( rc!=SQLITE_OK ){
|
|
return rc;
|
|
}
|
|
pPager->state = SQLITE_WRITELOCK;
|
|
pPager->dirtyFile = 0;
|
|
if( pPager->useJournal && !pPager->tempFile ){
|
|
rc = pager_open_journal(pPager);
|
|
}
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Mark a data page as writeable. The page is written into the journal
|
|
** if it is not there already. This routine must be called before making
|
|
** changes to a page.
|
|
**
|
|
** The first time this routine is called, the pager creates a new
|
|
** journal and acquires a write lock on the database. If the write
|
|
** lock could not be acquired, this routine returns SQLITE_BUSY. The
|
|
** calling routine must check for that return value and be careful not to
|
|
** change any page data until this routine returns SQLITE_OK.
|
|
**
|
|
** If the journal file could not be written because the disk is full,
|
|
** then this routine returns SQLITE_FULL and does an immediate rollback.
|
|
** All subsequent write attempts also return SQLITE_FULL until there
|
|
** is a call to sqlitepager_commit() or sqlitepager_rollback() to
|
|
** reset.
|
|
*/
|
|
int sqlitepager_write(void *pData){
|
|
PgHdr *pPg = DATA_TO_PGHDR(pData);
|
|
Pager *pPager = pPg->pPager;
|
|
int rc = SQLITE_OK;
|
|
|
|
/* Check for errors
|
|
*/
|
|
if( pPager->errMask ){
|
|
return pager_errcode(pPager);
|
|
}
|
|
if( pPager->readOnly ){
|
|
return SQLITE_PERM;
|
|
}
|
|
|
|
/* Mark the page as dirty. If the page has already been written
|
|
** to the journal then we can return right away.
|
|
*/
|
|
pPg->dirty = 1;
|
|
if( pPg->inJournal && (pPg->inCkpt || pPager->ckptInUse==0) ){
|
|
pPager->dirtyFile = 1;
|
|
return SQLITE_OK;
|
|
}
|
|
|
|
/* If we get this far, it means that the page needs to be
|
|
** written to the transaction journal or the ckeckpoint journal
|
|
** or both.
|
|
**
|
|
** First check to see that the transaction journal exists and
|
|
** create it if it does not.
|
|
*/
|
|
assert( pPager->state!=SQLITE_UNLOCK );
|
|
rc = sqlitepager_begin(pData);
|
|
if( rc!=SQLITE_OK ){
|
|
return rc;
|
|
}
|
|
assert( pPager->state==SQLITE_WRITELOCK );
|
|
if( !pPager->journalOpen && pPager->useJournal ){
|
|
rc = pager_open_journal(pPager);
|
|
if( rc!=SQLITE_OK ) return rc;
|
|
}
|
|
assert( pPager->journalOpen || !pPager->useJournal );
|
|
pPager->dirtyFile = 1;
|
|
|
|
/* The transaction journal now exists and we have a write lock on the
|
|
** main database file. Write the current page to the transaction
|
|
** journal if it is not there already.
|
|
*/
|
|
if( !pPg->inJournal && pPager->useJournal
|
|
&& (int)pPg->pgno <= pPager->origDbSize ){
|
|
rc = write32bits(&pPager->jfd, pPg->pgno);
|
|
if( rc==SQLITE_OK ){
|
|
rc = sqliteOsWrite(&pPager->jfd, pData, SQLITE_PAGE_SIZE);
|
|
}
|
|
if( rc!=SQLITE_OK ){
|
|
sqlitepager_rollback(pPager);
|
|
pPager->errMask |= PAGER_ERR_FULL;
|
|
return rc;
|
|
}
|
|
assert( pPager->aInJournal!=0 );
|
|
pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
|
|
pPager->needSync = !pPager->noSync;
|
|
pPg->inJournal = 1;
|
|
if( pPager->ckptInUse ){
|
|
pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
|
|
page_add_to_ckpt_list(pPg);
|
|
}
|
|
}
|
|
|
|
/* If the checkpoint journal is open and the page is not in it,
|
|
** then write the current page to the checkpoint journal.
|
|
*/
|
|
if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){
|
|
assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
|
|
rc = write32bits(&pPager->cpfd, pPg->pgno);
|
|
if( rc==SQLITE_OK ){
|
|
rc = sqliteOsWrite(&pPager->cpfd, pData, SQLITE_PAGE_SIZE);
|
|
}
|
|
if( rc!=SQLITE_OK ){
|
|
sqlitepager_rollback(pPager);
|
|
pPager->errMask |= PAGER_ERR_FULL;
|
|
return rc;
|
|
}
|
|
assert( pPager->aInCkpt!=0 );
|
|
pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
|
|
page_add_to_ckpt_list(pPg);
|
|
}
|
|
|
|
/* Update the database size and return.
|
|
*/
|
|
if( pPager->dbSize<(int)pPg->pgno ){
|
|
pPager->dbSize = pPg->pgno;
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Return TRUE if the page given in the argument was previously passed
|
|
** to sqlitepager_write(). In other words, return TRUE if it is ok
|
|
** to change the content of the page.
|
|
*/
|
|
int sqlitepager_iswriteable(void *pData){
|
|
PgHdr *pPg = DATA_TO_PGHDR(pData);
|
|
return pPg->dirty;
|
|
}
|
|
|
|
/*
|
|
** A call to this routine tells the pager that it is not necessary to
|
|
** write the information on page "pgno" back to the disk, even though
|
|
** that page might be marked as dirty.
|
|
**
|
|
** 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
|
|
** on the disk ends up being too small, that can lead to database
|
|
** corruption during the next transaction.
|
|
*/
|
|
}else{
|
|
pPg->dirty = 0;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
** A call to this routine tells the pager that if a rollback occurs,
|
|
** it is not necessary to restore the data on the given page. This
|
|
** means that the pager does not have to record the given page in the
|
|
** 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 || pPager->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);
|
|
page_add_to_ckpt_list(pPg);
|
|
}
|
|
}
|
|
if( pPager->ckptInUse && !pPg->inCkpt && (int)pPg->pgno<=pPager->ckptSize ){
|
|
assert( pPg->inJournal || (int)pPg->pgno>pPager->origDbSize );
|
|
assert( pPager->aInCkpt!=0 );
|
|
pPager->aInCkpt[pPg->pgno/8] |= 1<<(pPg->pgno&7);
|
|
page_add_to_ckpt_list(pPg);
|
|
}
|
|
}
|
|
|
|
/*
|
|
** Commit all changes to the database and release the write lock.
|
|
**
|
|
** If the commit fails for any reason, a rollback attempt is made
|
|
** and an error code is returned. If the commit worked, SQLITE_OK
|
|
** is returned.
|
|
*/
|
|
int sqlitepager_commit(Pager *pPager){
|
|
int rc;
|
|
PgHdr *pPg;
|
|
|
|
if( pPager->errMask==PAGER_ERR_FULL ){
|
|
rc = sqlitepager_rollback(pPager);
|
|
if( rc==SQLITE_OK ){
|
|
rc = SQLITE_FULL;
|
|
}
|
|
return rc;
|
|
}
|
|
if( pPager->errMask!=0 ){
|
|
rc = pager_errcode(pPager);
|
|
return rc;
|
|
}
|
|
if( pPager->state!=SQLITE_WRITELOCK ){
|
|
return SQLITE_ERROR;
|
|
}
|
|
if( pPager->dirtyFile==0 ){
|
|
/* Exit early (without doing the time-consuming sqliteOsSync() calls)
|
|
** if there have been no changes to the database file. */
|
|
rc = pager_unwritelock(pPager);
|
|
pPager->dbSize = -1;
|
|
return rc;
|
|
}
|
|
assert( pPager->journalOpen );
|
|
if( pPager->needSync && sqliteOsSync(&pPager->jfd)!=SQLITE_OK ){
|
|
goto commit_abort;
|
|
}
|
|
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
|
|
if( pPg->dirty==0 ) continue;
|
|
rc = sqliteOsSeek(&pPager->fd, (pPg->pgno-1)*(off_t)SQLITE_PAGE_SIZE);
|
|
if( rc!=SQLITE_OK ) goto commit_abort;
|
|
rc = sqliteOsWrite(&pPager->fd, PGHDR_TO_DATA(pPg), SQLITE_PAGE_SIZE);
|
|
if( rc!=SQLITE_OK ) goto commit_abort;
|
|
}
|
|
if( !pPager->noSync && sqliteOsSync(&pPager->fd)!=SQLITE_OK ){
|
|
goto commit_abort;
|
|
}
|
|
rc = pager_unwritelock(pPager);
|
|
pPager->dbSize = -1;
|
|
return rc;
|
|
|
|
/* Jump here if anything goes wrong during the commit process.
|
|
*/
|
|
commit_abort:
|
|
rc = sqlitepager_rollback(pPager);
|
|
if( rc==SQLITE_OK ){
|
|
rc = SQLITE_FULL;
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Rollback all changes. The database falls back to read-only mode.
|
|
** All in-memory cache pages revert to their original data contents.
|
|
** The journal is deleted.
|
|
**
|
|
** This routine cannot fail unless some other process is not following
|
|
** the correct locking protocol (SQLITE_PROTOCOL) or unless some other
|
|
** process is writing trash into the journal file (SQLITE_CORRUPT) or
|
|
** unless a prior malloc() failed (SQLITE_NOMEM). Appropriate error
|
|
** codes are returned for all these occasions. Otherwise,
|
|
** SQLITE_OK is returned.
|
|
*/
|
|
int sqlitepager_rollback(Pager *pPager){
|
|
int rc;
|
|
if( !pPager->dirtyFile || !pPager->journalOpen ){
|
|
rc = pager_unwritelock(pPager);
|
|
pPager->dbSize = -1;
|
|
return rc;
|
|
}
|
|
if( pPager->errMask!=0 && pPager->errMask!=PAGER_ERR_FULL ){
|
|
if( pPager->state>=SQLITE_WRITELOCK ){
|
|
pager_playback(pPager);
|
|
}
|
|
return pager_errcode(pPager);
|
|
}
|
|
if( pPager->state!=SQLITE_WRITELOCK ){
|
|
return SQLITE_OK;
|
|
}
|
|
rc = pager_playback(pPager);
|
|
if( rc!=SQLITE_OK ){
|
|
rc = SQLITE_CORRUPT;
|
|
pPager->errMask |= PAGER_ERR_CORRUPT;
|
|
}
|
|
pPager->dbSize = -1;
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Return TRUE if the database file is opened read-only. Return FALSE
|
|
** if the database is (in theory) writable.
|
|
*/
|
|
int sqlitepager_isreadonly(Pager *pPager){
|
|
return pPager->readOnly;
|
|
}
|
|
|
|
/*
|
|
** This routine is used for testing and analysis only.
|
|
*/
|
|
int *sqlitepager_stats(Pager *pPager){
|
|
static int a[9];
|
|
a[0] = pPager->nRef;
|
|
a[1] = pPager->nPage;
|
|
a[2] = pPager->mxPage;
|
|
a[3] = pPager->dbSize;
|
|
a[4] = pPager->state;
|
|
a[5] = pPager->errMask;
|
|
a[6] = pPager->nHit;
|
|
a[7] = pPager->nMiss;
|
|
a[8] = pPager->nOvfl;
|
|
return a;
|
|
}
|
|
|
|
/*
|
|
** Set the checkpoint.
|
|
**
|
|
** This routine should be called with the transaction journal already
|
|
** open. A new checkpoint journal is created that can be used to rollback
|
|
** changes of a single SQL command within a larger transaction.
|
|
*/
|
|
int sqlitepager_ckpt_begin(Pager *pPager){
|
|
int rc;
|
|
char zTemp[SQLITE_TEMPNAME_SIZE];
|
|
if( !pPager->journalOpen ){
|
|
pPager->ckptAutoopen = 1;
|
|
return SQLITE_OK;
|
|
}
|
|
assert( pPager->journalOpen );
|
|
assert( !pPager->ckptInUse );
|
|
pPager->aInCkpt = sqliteMalloc( pPager->dbSize/8 + 1 );
|
|
if( pPager->aInCkpt==0 ){
|
|
sqliteOsReadLock(&pPager->fd);
|
|
return SQLITE_NOMEM;
|
|
}
|
|
rc = sqliteOsFileSize(&pPager->jfd, &pPager->ckptJSize);
|
|
if( rc ) goto ckpt_begin_failed;
|
|
pPager->ckptSize = pPager->dbSize;
|
|
if( !pPager->ckptOpen ){
|
|
rc = sqlitepager_opentemp(zTemp, &pPager->cpfd);
|
|
if( rc ) goto ckpt_begin_failed;
|
|
pPager->ckptOpen = 1;
|
|
}
|
|
pPager->ckptInUse = 1;
|
|
return SQLITE_OK;
|
|
|
|
ckpt_begin_failed:
|
|
if( pPager->aInCkpt ){
|
|
sqliteFree(pPager->aInCkpt);
|
|
pPager->aInCkpt = 0;
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Commit a checkpoint.
|
|
*/
|
|
int sqlitepager_ckpt_commit(Pager *pPager){
|
|
if( pPager->ckptInUse ){
|
|
PgHdr *pPg, *pNext;
|
|
sqliteOsSeek(&pPager->cpfd, 0);
|
|
sqliteOsTruncate(&pPager->cpfd, 0);
|
|
pPager->ckptInUse = 0;
|
|
sqliteFree( pPager->aInCkpt );
|
|
pPager->aInCkpt = 0;
|
|
for(pPg=pPager->pCkpt; pPg; pPg=pNext){
|
|
pNext = pPg->pNextCkpt;
|
|
assert( pPg->inCkpt );
|
|
pPg->inCkpt = 0;
|
|
pPg->pPrevCkpt = pPg->pNextCkpt = 0;
|
|
}
|
|
pPager->pCkpt = 0;
|
|
}
|
|
pPager->ckptAutoopen = 0;
|
|
return SQLITE_OK;
|
|
}
|
|
|
|
/*
|
|
** Rollback a checkpoint.
|
|
*/
|
|
int sqlitepager_ckpt_rollback(Pager *pPager){
|
|
int rc;
|
|
if( pPager->ckptInUse ){
|
|
rc = pager_ckpt_playback(pPager);
|
|
sqlitepager_ckpt_commit(pPager);
|
|
}else{
|
|
rc = SQLITE_OK;
|
|
}
|
|
pPager->ckptAutoopen = 0;
|
|
return rc;
|
|
}
|
|
|
|
#ifdef SQLITE_TEST
|
|
/*
|
|
** Print a listing of all referenced pages and their ref count.
|
|
*/
|
|
void sqlitepager_refdump(Pager *pPager){
|
|
PgHdr *pPg;
|
|
for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
|
|
if( pPg->nRef<=0 ) continue;
|
|
printf("PAGE %3d addr=0x%08x nRef=%d\n",
|
|
pPg->pgno, (int)PGHDR_TO_DATA(pPg), pPg->nRef);
|
|
}
|
|
}
|
|
#endif
|