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Merge divergence-reduction changes into the bedrock branch.

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FossilOrigin-Name: ec5d7025cba9f4acaea984d5ec29b05b7f4b01f0e36e5287f27a16895ec42bf7
This commit is contained in:
drh
2024-12-16 18:29:31 +00:00
parent 3f79cb7b82 effc0d41f4
commit 602f13bdc9
4 changed files with 48 additions and 53 deletions
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31
src/wal.c
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@@ -884,7 +884,6 @@ struct WalIterator {
sizeof(ht_slot)*HASHTABLE_NSLOT + HASHTABLE_NPAGE*sizeof(u32) \
)
/*
** Structured Exception Handling (SEH) is a Windows-specific technique
** for catching exceptions raised while accessing memory-mapped files.
@@ -991,6 +990,7 @@ static void sehInjectFault(Wal *pWal){
# define SEH_SET_ON_ERROR(X,Y)
#endif /* ifdef SQLITE_USE_SEH */
/*
** Obtain a pointer to the iPage'th page of the wal-index. The wal-index
** is broken into pages of WALINDEX_PGSZ bytes. Wal-index pages are
@@ -3759,15 +3759,16 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int *pCnt){
pWal->readLock = eLock;
}
assert( pWal->minFrame==0 && walFramePage(pWal->minFrame)==0 );
}else{
}else
{
u32 mxReadMark; /* Largest aReadMark[] value */
int mxI; /* Index of largest aReadMark[] value */
int i; /* Loop counter */
u32 mxFrame; /* Wal frame to lock to */
if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame
#ifdef SQLITE_ENABLE_SNAPSHOT
#ifdef SQLITE_ENABLE_SNAPSHOT
&& ((pWal->bGetSnapshot==0 && pWal->pSnapshot==0) || pWal->hdr.mxFrame==0)
#endif
#endif
){
/* The WAL has been completely backfilled (or it is empty).
** and can be safely ignored.
@@ -3783,7 +3784,7 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int *pCnt){
** snapshot. Since holding READ_LOCK(0) prevents a checkpoint from
** happening, this is usually correct.
**
** However, if frames have been appended to the log (or if the log
** However, if frames have been appended to the log (or if the log
** is wrapped and written for that matter) before the READ_LOCK(0)
** is obtained, that is not necessarily true. A checkpointer may
** have started to backfill the appended frames but crashed before
@@ -3807,11 +3808,11 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int *pCnt){
mxReadMark = 0;
mxI = 0;
mxFrame = pWal->hdr.mxFrame;
#ifdef SQLITE_ENABLE_SNAPSHOT
#ifdef SQLITE_ENABLE_SNAPSHOT
if( pWal->pSnapshot && pWal->pSnapshot->mxFrame<mxFrame ){
mxFrame = pWal->pSnapshot->mxFrame;
}
#endif
#endif
for(i=1; i<WAL_NREADER; i++){
u32 thisMark = AtomicLoad(pInfo->aReadMark+i); SEH_INJECT_FAULT;
if( mxReadMark<=thisMark && thisMark<=mxFrame ){
@@ -3854,7 +3855,6 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int *pCnt){
#endif
assert((rc&0xFF)!=SQLITE_BUSY||rc==SQLITE_BUSY||rc==SQLITE_BUSY_TIMEOUT);
return (rc&0xFF)==SQLITE_BUSY ? WAL_RETRY : rc;
}
/* Now that the read-lock has been obtained, check that neither the
** value in the aReadMark[] array or the contents of the wal-index
@@ -3876,9 +3876,9 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int *pCnt){
** to read any frames earlier than minFrame from the wal file - they
** can be safely read directly from the database file.
**
** Because a ShmBarrier() call is made between taking the copy of
** Because a ShmBarrier() call is made between taking the copy of
** nBackfill and checking that the wal-header in shared-memory still
** matches the one cached in pWal->hdr, it is guaranteed that the
** matches the one cached in pWal->hdr, it is guaranteed that the
** checkpointer that set nBackfill was not working with a wal-index
** header newer than that cached in pWal->hdr. If it were, that could
** cause a problem. The checkpointer could omit to checkpoint
@@ -4151,7 +4151,6 @@ int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
return rc;
}
/*
** Finish with a read transaction. All this does is release the
** read-lock.
@@ -4693,7 +4692,6 @@ static int walLockForCommit(
}
}
}
pWal->nPriorFrame = walGetPriorFrame(&pWal->hdr);
return rc;
}
@@ -5039,7 +5037,6 @@ static int walRestartLog(Wal *pWal){
** to the wal file. */
rc = walUpgradeReadlock(pWal);
}
pWal->nPriorFrame = walGetPriorFrame(&pWal->hdr);
return rc;
}
@@ -5440,7 +5437,6 @@ static int walFrames(
return rc;
}
/*
** Write a set of frames to the log. The caller must hold the write-lock
** on the log file (obtained using sqlite3WalBeginWriteTransaction()).
@@ -5566,7 +5562,7 @@ int sqlite3WalCheckpoint(
}else{
rc = walCheckpoint(pWal, db, eMode2, xBusy2, pBusyArg, sync_flags,zBuf);
}
/* If no error occurred, set the output variables. */
if( rc==SQLITE_OK || rc==SQLITE_BUSY ){
if( pnLog ){
@@ -5660,7 +5656,6 @@ int sqlite3WalCallback(Wal *pWal){
*/
int sqlite3WalExclusiveMode(Wal *pWal, int op){
int rc;
assert( pWal->writeLock==0 );
assert( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE || op==-1 );
@@ -5723,7 +5718,7 @@ int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot){
assert( pWal->readLock>=0 && pWal->writeLock==0 );
if( memcmp(&pWal->hdr.aFrameCksum[0],aZero,8)==0 ){
if( memcmp(&pWal->hdr.aFrameCksum[0],aZero,16)==0 ){
*ppSnapshot = 0;
return SQLITE_ERROR;
}
@@ -5806,7 +5801,7 @@ int sqlite3WalSnapshotCheck(Wal *pWal, sqlite3_snapshot *pSnapshot){
}
}
}
SEH_EXCEPT( rc = walHandleException(pWal) );
SEH_EXCEPT( rc = walHandleException(pWal); )
return rc;
}