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Add support for DEFERRED, IMMEDIATE, and EXCLUSIVE transactions. (CVS 2000)

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FossilOrigin-Name: 81ff8107ad63113782cf5a9ba7a512496114ba08
This commit is contained in:
drh
2004-10-05 02:41:42 +00:00
parent 9a43267ba2
commit 684917c269
18 changed files with 249 additions and 119 deletions
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114
src/pager.c
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@@ -18,7 +18,7 @@
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.166 2004/10/02 20:38:28 drh Exp $
** @(#) $Id: pager.c,v 1.167 2004/10/05 02:41:43 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
@@ -88,11 +88,27 @@
** or sqlite_pager_commit(), the state goes back to PAGER_SHARED.
*/
#define PAGER_UNLOCK 0
#define PAGER_SHARED 1
#define PAGER_RESERVED 2
#define PAGER_EXCLUSIVE 3
#define PAGER_SYNCED 4
#define PAGER_SHARED 1 /* same as SHARED_LOCK */
#define PAGER_RESERVED 2 /* same as RESERVED_LOCK */
#define PAGER_EXCLUSIVE 4 /* same as EXCLUSIVE_LOCK */
#define PAGER_SYNCED 5
/*
** If the SQLITE_BUSY_RESERVED_LOCK macro is set to true at compile-time,
** then failed attempts to get a reserved lock will invoke the busy callback.
** This is off by default. To see why, consider the following scenario:
**
** Suppose thread A already has a shared lock and wants a reserved lock.
** Thread B already has a reserved lock and wants an exclusive lock. If
** both threads are using their busy callbacks, it might be a long time
** be for one of the threads give up and allows the other to proceed.
** But if the thread trying to get the reserved lock gives up quickly
** (if it never invokes its busy callback) then the contention will be
** resolved quickly.
*/
#ifndef SQLITE_BUSY_RESERVED_LOCK
# define SQLITE_BUSY_RESERVED_LOCK 0
#endif
/*
** Each in-memory image of a page begins with the following header.
@@ -1907,6 +1923,37 @@ static int syncJournal(Pager *pPager){
return rc;
}
/*
** Try to obtain a lock on a file. Invoke the busy callback if the lock
** is currently not available. Repeate until the busy callback returns
** false or until the lock succeeds.
**
** Return SQLITE_OK on success and an error code if we cannot obtain
** the lock.
*/
static int pager_wait_on_lock(Pager *pPager, int locktype){
int rc;
assert( PAGER_SHARED==SHARED_LOCK );
assert( PAGER_RESERVED==RESERVED_LOCK );
assert( PAGER_EXCLUSIVE==EXCLUSIVE_LOCK );
if( pPager->state>=locktype ){
rc = SQLITE_OK;
}else{
int busy = 1;
do {
rc = sqlite3OsLock(&pPager->fd, locktype);
}while( rc==SQLITE_BUSY &&
pPager->pBusyHandler &&
pPager->pBusyHandler->xFunc &&
pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++)
);
if( rc==SQLITE_OK ){
pPager->state = locktype;
}
}
return rc;
}
/*
** Given a list of pages (connected by the PgHdr.pDirty pointer) write
** every one of those pages out to the database file and mark them all
@@ -1915,7 +1962,6 @@ static int syncJournal(Pager *pPager){
static int pager_write_pagelist(PgHdr *pList){
Pager *pPager;
int rc;
int busy = 1;
if( pList==0 ) return SQLITE_OK;
pPager = pList->pPager;
@@ -1936,17 +1982,10 @@ static int pager_write_pagelist(PgHdr *pList){
** EXCLUSIVE, it means the database file has been changed and any rollback
** will require a journal playback.
*/
do {
rc = sqlite3OsLock(&pPager->fd, EXCLUSIVE_LOCK);
}while( rc==SQLITE_BUSY &&
pPager->pBusyHandler &&
pPager->pBusyHandler->xFunc &&
pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++)
);
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
return rc;
}
pPager->state = PAGER_EXCLUSIVE;
while( pList ){
assert( pList->dirty );
@@ -2019,18 +2058,10 @@ int sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage){
** on the database file.
*/
if( pPager->nRef==0 && !pPager->memDb ){
int busy = 1;
do {
rc = sqlite3OsLock(&pPager->fd, SHARED_LOCK);
}while( rc==SQLITE_BUSY &&
pPager->pBusyHandler &&
pPager->pBusyHandler->xFunc &&
pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++)
);
rc = pager_wait_on_lock(pPager, SHARED_LOCK);
if( rc!=SQLITE_OK ){
return rc;
}
pPager->state = PAGER_SHARED;
/* If a journal file exists, and there is no RESERVED lock on the
** database file, then it either needs to be played back or deleted.
@@ -2408,8 +2439,12 @@ failed_to_open_journal:
** actual need to write to the journal.
**
** If the database is already reserved for writing, this routine is a no-op.
**
** If exFlag is true, go ahead and get an EXCLUSIVE lock on the file
** immediately instead of waiting until we try to flush the cache. The
** exFlag is ignored if a transaction is already active.
*/
int sqlite3pager_begin(void *pData){
int sqlite3pager_begin(void *pData, int exFlag){
PgHdr *pPg = DATA_TO_PGHDR(pData);
Pager *pPager = pPg->pPager;
int rc = SQLITE_OK;
@@ -2421,29 +2456,20 @@ int sqlite3pager_begin(void *pData){
pPager->state = PAGER_EXCLUSIVE;
pPager->origDbSize = pPager->dbSize;
}else{
#ifdef SQLITE_BUSY_RESERVED_LOCK
int busy = 1;
do {
if( SQLITE_BUSY_RESERVED_LOCK || exFlag ){
rc = pager_wait_on_lock(pPager, RESERVED_LOCK);
}else{
rc = sqlite3OsLock(&pPager->fd, RESERVED_LOCK);
}while( rc==SQLITE_BUSY &&
pPager->pBusyHandler &&
pPager->pBusyHandler->xFunc &&
pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++)
);
#else
rc = sqlite3OsLock(&pPager->fd, RESERVED_LOCK);
#endif
}
if( rc==SQLITE_OK ){
pPager->state = PAGER_RESERVED;
if( exFlag ){
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
}
}
if( rc!=SQLITE_OK ){
/* We do not call the busy handler when we fail to get a reserved lock.
** The only reason we might fail is because another process is holding
** the reserved lock. But the other process will not be able to
** release its reserved lock until this process releases its shared
** lock. So we might as well fail in this process, let it release
** its shared lock so that the other process can commit.
*/
return rc;
}
pPager->state = PAGER_RESERVED;
pPager->dirtyCache = 0;
TRACE2("TRANSACTION %d\n", pPager->fd.h);
if( pPager->useJournal && !pPager->tempFile ){
@@ -2504,7 +2530,7 @@ int sqlite3pager_write(void *pData){
** create it if it does not.
*/
assert( pPager->state!=PAGER_UNLOCK );
rc = sqlite3pager_begin(pData);
rc = sqlite3pager_begin(pData, 0);
if( rc!=SQLITE_OK ){
return rc;
}