database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-08-05 15:55:57 +03:00
Code Activity

Remove entries from wal-index hash tables when a rollback or savepoint rollback occurs.

Browse Source 
FossilOrigin-Name: 36795c2b23a78978528cace193e386138adacd41
This commit is contained in:
dan
2010-05-21 15:31:56 +00:00
parent f0b20f8801
commit 6f1501481f
4 changed files with 84 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

55
src/wal.c
View File

@@ -193,8 +193,9 @@
** second reader using K1 will see additional values that were inserted
** later, which is exactly what reader two wants.
**
** When a rollback occurs, the value of K is decreased. This has the
** effect of automatically removing entries from the hash table.
** When a rollback occurs, the value of K is decreased. Hash table entries
** that correspond to frames greater than the new K value are removed
** from the hash table at this point.
*/
#ifndef SQLITE_OMIT_WAL
@@ -644,10 +645,10 @@ static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
walHashFind(pWal, iFrame, &aHash, &aPgno, &iZero);
idx = iFrame - iZero;
if( idx==1 ) memset((void*)aHash, 0xff, HASHTABLE_NBYTE);
if( idx==1 ) memset((void*)aHash, 0, HASHTABLE_NBYTE);
assert( idx <= HASHTABLE_NSLOT/2 + 1 );
aPgno[iFrame] = iPage;
for(iKey=walHash(iPage); aHash[iKey]<idx; iKey=walNextHash(iKey)){
for(iKey=walHash(iPage); aHash[iKey]; iKey=walNextHash(iKey)){
assert( nCollide++ < idx );
}
aHash[iKey] = idx;
@@ -1382,9 +1383,9 @@ int sqlite3WalRead(
walHashFind(pWal, iHash, &aHash, &aPgno, &iZero);
mxHash = iLast - iZero;
if( mxHash > HASHTABLE_NPAGE ) mxHash = HASHTABLE_NPAGE;
for(iKey=walHash(pgno); aHash[iKey]<=mxHash; iKey=walNextHash(iKey)){
for(iKey=walHash(pgno); aHash[iKey]; iKey=walNextHash(iKey)){
u32 iFrame = aHash[iKey] + iZero;
if( ALWAYS(iFrame<=iLast) && aPgno[iFrame]==pgno && iFrame>iRead ){
if( iFrame<=iLast && aPgno[iFrame]==pgno && iFrame>iRead ){
iRead = iFrame;
}
}
@@ -1465,6 +1466,40 @@ int sqlite3WalWriteLock(Wal *pWal, int op){
return rc;
}
/*
** Remove entries from zero or more hash-table indexes in the wal-index
** file.
**
** This function is called when rolling back a transaction or savepoint
** transaction in WAL mode. Argument iNewMx is the value that
** Wal.hdr.mxFrame will be set to following the rollback. Argument iOldMx
** is the value that it had before the rollback. This function removes
** entries that refer to frames with frame numbers greater than iNewMx
** from the hash table that contains the entry associated with iNewMx.
** It is not necessary to remove any entries from any subsequent hash
** tables, as they will be zeroed by walIndexAppend() before they are
** next used.
*/
static void walClearHash(Wal *pWal, u32 iOldMx, u32 iNewMx){
if( iOldMx>iNewMx ){
volatile HASHTABLE_DATATYPE *aHash; /* Pointer to hash table to clear */
volatile u32 *unused1; /* Only to satisfy walHashFind() */
u32 iZero; /* frame == (aHash[x]+iZero) */
int iLimit; /* Zero values greater than this */
walHashFind(pWal, iNewMx+1, &aHash, &unused1, &iZero);
iLimit = iNewMx - iZero;
if( iLimit>0 ){
int i; /* Used to iterate through aHash[] */
for(i=1; i<=HASHTABLE_NPAGE; i++){
if( aHash[i]>iLimit ){
aHash[i] = 0;
}
}
}
}
}
/*
** If any data has been written (but not committed) to the log file, this
** function moves the write-pointer back to the start of the transaction.
@@ -1490,6 +1525,9 @@ int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx){
assert( pWal->lockState==SQLITE_SHM_WRITE );
rc = xUndo(pUndoCtx, pWal->pWiData[walIndexEntry(iFrame)]);
}
if( rc==SQLITE_OK ){
walClearHash(pWal, iMax, pWal->hdr.mxFrame);
}
walIndexUnmap(pWal);
}
return rc;
@@ -1510,6 +1548,11 @@ int sqlite3WalSavepointUndo(Wal *pWal, u32 iFrame){
int rc = SQLITE_OK;
assert( pWal->lockState==SQLITE_SHM_WRITE );
rc = walIndexMap(pWal, walMappingSize(pWal->hdr.mxFrame));
if( rc==SQLITE_OK ){
walClearHash(pWal, pWal->hdr.mxFrame, iFrame);
walIndexUnmap(pWal);
}
pWal->hdr.mxFrame = iFrame;
return rc;
}