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In _bt_check_unique() loop, don't bother applying _bt_isequal() to

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killed items; just skip to the next item immediately.  Only check for
key equality when we reach a non-killed item or the end of the index
page.  This saves key comparisons when there are lots of killed items,
as for example in a heavily-updated table that's not been vacuumed lately.
Seems to be a win for pgbench anyway.
This commit is contained in:
Tom Lane 2003-09-02 22:10:16 +00:00
parent 30b4abf5d0
commit 5ac2d7c0eb
1 changed files with 27 additions and 15 deletions
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42
src/backend/access/nbtree/nbtinsert.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.104 2003/08/04 02:39:57 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.105 2003/09/02 22:10:16 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -189,27 +189,39 @@ _bt_check_unique(Relation rel, BTItem btitem, Relation heapRel,
BlockNumber nblkno;
/*
* make sure the offset points to an actual key before trying to
* compare it...
* make sure the offset points to an actual item before trying to
* examine it...
*/
if (offset <= maxoff)
{
/*
* _bt_compare returns 0 for (1,NULL) and (1,NULL) - this's
* how we handling NULLs - and so we must not use _bt_compare
* in real comparison, but only for ordering/finding items on
* pages. - vadim 03/24/97
*/
if (!_bt_isequal(itupdesc, page, offset, natts, itup_scankey))
break; /* we're past all the equal tuples */
curitemid = PageGetItemId(page, offset);
/*
* We can skip the heap fetch if the item is marked killed.
* We can skip items that are marked killed.
*
* Formerly, we applied _bt_isequal() before checking the kill
* flag, so as to fall out of the item loop as soon as possible.
* However, in the presence of heavy update activity an index
* may contain many killed items with the same key; running
* _bt_isequal() on each killed item gets expensive. Furthermore
* it is likely that the non-killed version of each key appears
* first, so that we didn't actually get to exit any sooner anyway.
* So now we just advance over killed items as quickly as we can.
* We only apply _bt_isequal() when we get to a non-killed item or
* the end of the page.
*/
if (!ItemIdDeleted(curitemid))
{
/*
* _bt_compare returns 0 for (1,NULL) and (1,NULL) - this's
* how we handling NULLs - and so we must not use _bt_compare
* in real comparison, but only for ordering/finding items on
* pages. - vadim 03/24/97
*/
if (!_bt_isequal(itupdesc, page, offset, natts, itup_scankey))
break; /* we're past all the equal tuples */
/* okay, we gotta fetch the heap tuple ... */
cbti = (BTItem) PageGetItem(page, curitemid);
htup.t_self = cbti->bti_itup.t_tid;
if (heap_fetch(heapRel, SnapshotDirty, &htup, &hbuffer,
@ -1547,7 +1559,7 @@ _bt_pgaddtup(Relation rel,
* _bt_isequal - used in _bt_doinsert in check for duplicates.
*
* This is very similar to _bt_compare, except for NULL handling.
* Rule is simple: NOT_NULL not equal NULL, NULL not_equal NULL too.
* Rule is simple: NOT_NULL not equal NULL, NULL not equal NULL too.
*/
static bool
_bt_isequal(TupleDesc itupdesc, Page page, OffsetNumber offnum,
@ -1576,7 +1588,7 @@ _bt_isequal(TupleDesc itupdesc, Page page, OffsetNumber offnum,
datum = index_getattr(itup, attno, itupdesc, &isNull);
/* NULLs are never equal to anything */
if (entry->sk_flags & SK_ISNULL || isNull)
if ((entry->sk_flags & SK_ISNULL) || isNull)
return false;
result = DatumGetInt32(FunctionCall2(&entry->sk_func,