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Add untested implementations of experimental APIs sqlite3_snapshot_get(), _open() and _free().

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FossilOrigin-Name: 0715eb00aa8891400cd50a15509d3d7b13789626
This commit is contained in:
dan
2015-12-05 20:51:54 +00:00
parent 28a6a1168b
commit fc1acf33b8
9 changed files with 320 additions and 18 deletions
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78
src/wal.c
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@ -434,6 +434,9 @@ struct Wal {
#ifdef SQLITE_DEBUG
u8 lockError; /* True if a locking error has occurred */
#endif
#ifdef SQLITE_ENABLE_SNAPSHOT
WalIndexHdr *pSnapshot;
#endif
};
/*
@ -2147,6 +2150,7 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
int mxI; /* Index of largest aReadMark[] value */
int i; /* Loop counter */
int rc = SQLITE_OK; /* Return code */
int mxFrame; /* Wal frame to lock to */
assert( pWal->readLock<0 ); /* Not currently locked */
@ -2210,7 +2214,12 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
}
pInfo = walCkptInfo(pWal);
if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame ){
if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame
#ifdef SQLITE_ENABLE_SNAPSHOT
&& (pWal->pSnapshot==0 || pWal->hdr.mxFrame==0
|| 0==memcmp(&pWal->hdr, pWal->pSnapshot, sizeof(WalIndexHdr)))
#endif
){
/* The WAL has been completely backfilled (or it is empty).
** and can be safely ignored.
*/
@ -2248,9 +2257,13 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
*/
mxReadMark = 0;
mxI = 0;
mxFrame = pWal->hdr.mxFrame;
#ifdef SQLITE_ENABLE_SNAPSHOT
if( pWal->pSnapshot ) mxFrame = pWal->pSnapshot->mxFrame;
#endif
for(i=1; i<WAL_NREADER; i++){
u32 thisMark = pInfo->aReadMark[i];
if( mxReadMark<=thisMark && thisMark<=pWal->hdr.mxFrame ){
if( mxReadMark<=thisMark && thisMark<=mxFrame ){
assert( thisMark!=READMARK_NOT_USED );
mxReadMark = thisMark;
mxI = i;
@ -2259,12 +2272,12 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
/* There was once an "if" here. The extra "{" is to preserve indentation. */
{
if( (pWal->readOnly & WAL_SHM_RDONLY)==0
&& (mxReadMark<pWal->hdr.mxFrame || mxI==0)
&& (mxReadMark<mxFrame || mxI==0)
){
for(i=1; i<WAL_NREADER; i++){
rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
if( rc==SQLITE_OK ){
mxReadMark = pInfo->aReadMark[i] = pWal->hdr.mxFrame;
mxReadMark = pInfo->aReadMark[i] = mxFrame;
mxI = i;
walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
break;
@ -2349,6 +2362,14 @@ int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
int rc; /* Return code */
int cnt = 0; /* Number of TryBeginRead attempts */
#ifdef SQLITE_ENABLE_SNAPSHOT
int bChanged = 0;
WalIndexHdr *pSnapshot = pWal->pSnapshot;
if( pSnapshot && memcmp(pSnapshot, &pWal->hdr, sizeof(WalIndexHdr))){
bChanged = 1;
}
#endif
do{
rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
}while( rc==WAL_RETRY );
@ -2356,6 +2377,32 @@ int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
testcase( (rc&0xff)==SQLITE_IOERR );
testcase( rc==SQLITE_PROTOCOL );
testcase( rc==SQLITE_OK );
#ifdef SQLITE_ENABLE_SNAPSHOT
if( rc==SQLITE_OK ){
if( pSnapshot && memcmp(pSnapshot, &pWal->hdr, sizeof(WalIndexHdr)) ){
volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
rc = walLockShared(pWal, WAL_READ_LOCK(0));
if( rc==SQLITE_OK ){
if( pInfo->nBackfill<=pSnapshot->mxFrame
&& pSnapshot->aSalt[0]==pWal->hdr.aSalt[0]
&& pSnapshot->aSalt[1]==pWal->hdr.aSalt[1]
){
assert( pWal->readLock>0 );
assert( pInfo->aReadMark[pWal->readLock]<=pSnapshot->mxFrame );
memcpy(&pWal->hdr, pSnapshot, sizeof(WalIndexHdr));
*pChanged = bChanged;
}else{
rc = SQLITE_BUSY_SNAPSHOT;
}
walUnlockShared(pWal, WAL_READ_LOCK(0));
}
if( rc!=SQLITE_OK ){
sqlite3WalEndReadTransaction(pWal);
}
}
}
#endif
return rc;
}
@ -3165,6 +3212,29 @@ int sqlite3WalHeapMemory(Wal *pWal){
return (pWal && pWal->exclusiveMode==WAL_HEAPMEMORY_MODE );
}
#ifdef SQLITE_ENABLE_SNAPSHOT
int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot){
int rc = SQLITE_OK;
WalIndexHdr *pRet;
assert( pWal->readLock>=0 && pWal->writeLock==0 );
pRet = (WalIndexHdr*)sqlite3_malloc(sizeof(WalIndexHdr));
if( pRet==0 ){
rc = SQLITE_NOMEM;
}else{
memcpy(pRet, &pWal->hdr, sizeof(WalIndexHdr));
*ppSnapshot = (sqlite3_snapshot*)pRet;
}
return rc;
}
void sqlite3WalSnapshotOpen(Wal *pWal, sqlite3_snapshot *pSnapshot){
pWal->pSnapshot = (WalIndexHdr*)pSnapshot;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
#ifdef SQLITE_ENABLE_ZIPVFS
/*
** If the argument is not NULL, it points to a Wal object that holds a