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Add several EXPENSIVE_ASSERT code blocks to validate the wal-index hash table.

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Fix the bugs that these code blocks fine.  Rename walClearHash() to 
walCleanupHash() and simplify its interface.

FossilOrigin-Name: 7aade899e55f4565f02d301e1e83fb0bac2ea500
This commit is contained in:
drh
2010-05-22 00:55:39 +00:00
parent 3b1eca0ade
commit 4fa95bfc39
3 changed files with 96 additions and 43 deletions
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113
src/wal.c
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@@ -652,8 +652,36 @@ static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
assert( nCollide++ < idx );
}
aHash[iKey] = idx;
#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
/* Verify that the number of entries in the hash table exactly equals
** the number of entries in the mapping region.
*/
{
int i; /* Loop counter */
int nEntry = 0; /* Number of entries in the hash table */
for(i=0; i<HASHTABLE_NSLOT; i++){ if( aHash[i] ) nEntry++; }
assert( nEntry==idx );
}
/* Verify that the every entry in the mapping region is reachable
** via the hash table. This turns out to be a really, really expensive
** thing to check, so only do this occasionally - not on every
** iteration.
*/
if( (idx&0x3ff)==0 ){
int i; /* Loop counter */
for(i=1; i<=idx; i++){
for(iKey=walHash(aPgno[i+iZero]); aHash[iKey]; iKey=walNextHash(iKey)){
if( aHash[iKey]==i ) break;
}
assert( aHash[iKey]==i );
}
}
#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
}
return rc;
}
@@ -1467,37 +1495,49 @@ int sqlite3WalWriteLock(Wal *pWal, int op){
}
/*
** Remove entries from zero or more hash-table indexes in the wal-index
** file.
** Remove entries from the hash table that point to WAL slots greater
** than pWal->hdr.mxFrame.
**
** 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.
** This function is called whenever pWal->hdr.mxFrame is decreased due
** to a rollback or savepoint.
**
** At most only the very last hash table needs to be updated. Any
** later hash tables will be automatically cleared when pWal->hdr.mxFrame
** advances to the point where those hash tables are actually needed.
*/
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 */
static void walCleanupHash(Wal *pWal){
volatile HASHTABLE_DATATYPE *aHash; /* Pointer to hash table to clear */
volatile u32 *aPgno; /* Unused return from 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=0; i<HASHTABLE_NSLOT; i++){
if( aHash[i]>iLimit ){
aHash[i] = 0;
}
assert( pWal->lockState==SQLITE_SHM_WRITE );
walHashFind(pWal, pWal->hdr.mxFrame+1, &aHash, &aPgno, &iZero);
iLimit = pWal->hdr.mxFrame - iZero;
if( iLimit>0 ){
int i; /* Used to iterate through aHash[] */
for(i=0; i<HASHTABLE_NSLOT; i++){
if( aHash[i]>iLimit ){
aHash[i] = 0;
}
}
}
#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
/* Verify that the every entry in the mapping region is still reachable
** via the hash table even after the cleanup.
*/
{
int i; /* Loop counter */
int iKey; /* Hash key */
for(i=1; i<=iLimit; i++){
for(iKey=walHash(aPgno[i+iZero]); aHash[iKey]; iKey=walNextHash(iKey)){
if( aHash[iKey]==i ) break;
}
assert( aHash[iKey]==i );
}
}
#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
}
/*
@@ -1521,12 +1561,12 @@ int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx){
assert( pWal->pWiData==0 );
rc = walIndexReadHdr(pWal, &unused);
for(iFrame=pWal->hdr.mxFrame+1; rc==SQLITE_OK && iFrame<=iMax; iFrame++){
assert( pWal->lockState==SQLITE_SHM_WRITE );
rc = xUndo(pUndoCtx, pWal->pWiData[walIndexEntry(iFrame)]);
}
if( rc==SQLITE_OK ){
walClearHash(pWal, iMax, pWal->hdr.mxFrame);
walCleanupHash(pWal);
for(iFrame=pWal->hdr.mxFrame+1; rc==SQLITE_OK && iFrame<=iMax; iFrame++){
assert( pWal->lockState==SQLITE_SHM_WRITE );
rc = xUndo(pUndoCtx, pWal->pWiData[walIndexEntry(iFrame)]);
}
}
walIndexUnmap(pWal);
}
@@ -1548,12 +1588,15 @@ 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);
assert( iFrame<=pWal->hdr.mxFrame );
if( iFrame<pWal->hdr.mxFrame ){
rc = walIndexMap(pWal, walMappingSize(pWal->hdr.mxFrame));
pWal->hdr.mxFrame = iFrame;
if( rc==SQLITE_OK ){
walCleanupHash(pWal);
walIndexUnmap(pWal);
}
}
pWal->hdr.mxFrame = iFrame;
return rc;
}