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Remove the "rowid cache" that sought to remember the largest rowid for a

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table and thereby speed up OP_NewRowid.  That cache was ineffective.
Removing it results in a performance increase of 0.4%, less memory usage,
and a slightly smaller library size.

FossilOrigin-Name: 56bc5ce8958c8e6250531b4052b905d7ac993db3
This commit is contained in:
drh
2014-02-12 21:31:12 +00:00
parent 784156f84c
commit e0670b6220
6 changed files with 59 additions and 94 deletions
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45
src/btree.c
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@@ -3632,7 +3632,6 @@ static int btreeCursor(
}
pBt->pCursor = pCur;
pCur->eState = CURSOR_INVALID;
pCur->cachedRowid = 0;
return SQLITE_OK;
}
int sqlite3BtreeCursor(
@@ -3673,36 +3672,6 @@ void sqlite3BtreeCursorZero(BtCursor *p){
memset(p, 0, offsetof(BtCursor, iPage));
}
/*
** Set the cached rowid value of every cursor in the same database file
** as pCur and having the same root page number as pCur. The value is
** set to iRowid.
**
** Only positive rowid values are considered valid for this cache.
** The cache is initialized to zero, indicating an invalid cache.
** A btree will work fine with zero or negative rowids. We just cannot
** cache zero or negative rowids, which means tables that use zero or
** negative rowids might run a little slower. But in practice, zero
** or negative rowids are very uncommon so this should not be a problem.
*/
void sqlite3BtreeSetCachedRowid(BtCursor *pCur, sqlite3_int64 iRowid){
BtCursor *p;
for(p=pCur->pBt->pCursor; p; p=p->pNext){
if( p->pgnoRoot==pCur->pgnoRoot ) p->cachedRowid = iRowid;
}
assert( pCur->cachedRowid==iRowid );
}
/*
** Return the cached rowid for the given cursor. A negative or zero
** return value indicates that the rowid cache is invalid and should be
** ignored. If the rowid cache has never before been set, then a
** zero is returned.
*/
sqlite3_int64 sqlite3BtreeGetCachedRowid(BtCursor *pCur){
return pCur->cachedRowid;
}
/*
** Close a cursor. The read lock on the database file is released
** when the last cursor is closed.
@@ -6986,11 +6955,17 @@ int sqlite3BtreeInsert(
rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
if( rc ) return rc;
/* If this is an insert into a table b-tree, invalidate any incrblob
** cursors open on the row being replaced (assuming this is a replace
** operation - if it is not, the following is a no-op). */
if( pCur->pKeyInfo==0 ){
/* If this is an insert into a table b-tree, invalidate any incrblob
** cursors open on the row being replaced */
invalidateIncrblobCursors(p, nKey, 0);
/* If the cursor is currently on the last row and we are appending a
** new row onto the end, set the "loc" to avoid an unnecessary btreeMoveto()
** call */
if( pCur->validNKey && nKey>0 && pCur->info.nKey==nKey-1 ){
loc = -1;
}
}
if( !loc ){
@@ -7060,8 +7035,8 @@ int sqlite3BtreeInsert(
** row without seeking the cursor. This can be a big performance boost.
*/
pCur->info.nSize = 0;
pCur->validNKey = 0;
if( rc==SQLITE_OK && pPage->nOverflow ){
pCur->validNKey = 0;
rc = balance(pCur);
/* Must make sure nOverflow is reset to zero even if the balance()