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Mark index entries "killed" when they are no longer visible to any

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transaction, so as to avoid returning them out of the index AM.  Saves
repeated heap_fetch operations on frequently-updated rows.  Also detect
queries on unique keys (equality to all columns of a unique index), and
don't bother continuing scan once we have found first match.

Killing is implemented in the btree and hash AMs, but not yet in rtree
or gist, because there isn't an equally convenient place to do it in
those AMs (the outer amgetnext routine can't do it without re-pinning
the index page).

Did some small cleanup on APIs of HeapTupleSatisfies, heap_fetch, and
index_insert to make this a little easier.
This commit is contained in:
Tom Lane
2002-05-24 18:57:57 +00:00
parent 2f2d05763d
commit 3f4d488022
30 changed files with 498 additions and 273 deletions
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110
src/backend/access/nbtree/nbtinsert.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.90 2002/03/06 06:09:17 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.91 2002/05/24 18:57:55 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -176,7 +176,6 @@ _bt_check_unique(Relation rel, BTItem btitem, Relation heapRel,
Page page;
BTPageOpaque opaque;
Buffer nbuf = InvalidBuffer;
bool chtup = true;
page = BufferGetPage(buf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
@@ -194,70 +193,85 @@ _bt_check_unique(Relation rel, BTItem btitem, Relation heapRel,
for (;;)
{
HeapTupleData htup;
Buffer buffer;
Buffer hbuffer;
ItemId curitemid;
BTItem cbti;
BlockNumber nblkno;
/*
* _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
*
* make sure the offset points to an actual key before trying to
* compare 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);
/*
* Have to check is inserted heap tuple deleted one (i.e. just
* moved to another place by vacuum)! We only need to do this
* once, but don't want to do it at all unless we see equal
* tuples, so as not to slow down unequal case.
* We can skip the heap fetch if the item is marked killed.
*/
if (chtup)
if (!ItemIdDeleted(curitemid))
{
htup.t_self = btitem->bti_itup.t_tid;
heap_fetch(heapRel, SnapshotDirty, &htup, &buffer, NULL);
if (htup.t_data == NULL) /* YES! */
break;
/* Live tuple is being inserted, so continue checking */
ReleaseBuffer(buffer);
chtup = false;
}
cbti = (BTItem) PageGetItem(page, PageGetItemId(page, offset));
htup.t_self = cbti->bti_itup.t_tid;
heap_fetch(heapRel, SnapshotDirty, &htup, &buffer, NULL);
if (htup.t_data != NULL) /* it is a duplicate */
{
TransactionId xwait =
(TransactionIdIsValid(SnapshotDirty->xmin)) ?
SnapshotDirty->xmin : SnapshotDirty->xmax;
/*
* If this tuple is being updated by other transaction
* then we have to wait for its commit/abort.
*/
ReleaseBuffer(buffer);
if (TransactionIdIsValid(xwait))
cbti = (BTItem) PageGetItem(page, curitemid);
htup.t_self = cbti->bti_itup.t_tid;
if (heap_fetch(heapRel, SnapshotDirty, &htup, &hbuffer,
true, NULL))
{
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
/* Tell _bt_doinsert to wait... */
return xwait;
}
/* it is a duplicate */
TransactionId xwait =
(TransactionIdIsValid(SnapshotDirty->xmin)) ?
SnapshotDirty->xmin : SnapshotDirty->xmax;
/*
* Otherwise we have a definite conflict.
*/
elog(ERROR, "Cannot insert a duplicate key into unique index %s",
RelationGetRelationName(rel));
ReleaseBuffer(hbuffer);
/*
* If this tuple is being updated by other transaction
* then we have to wait for its commit/abort.
*/
if (TransactionIdIsValid(xwait))
{
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
/* Tell _bt_doinsert to wait... */
return xwait;
}
/*
* Otherwise we have a definite conflict.
*/
elog(ERROR, "Cannot insert a duplicate key into unique index %s",
RelationGetRelationName(rel));
}
else
{
/*
* Hmm, if we can't see the tuple, maybe it can be
* marked killed. This logic should match index_getnext
* and btgettuple.
*/
uint16 sv_infomask;
LockBuffer(hbuffer, BUFFER_LOCK_SHARE);
sv_infomask = htup.t_data->t_infomask;
if (HeapTupleSatisfiesVacuum(htup.t_data,
RecentGlobalXmin) ==
HEAPTUPLE_DEAD)
{
curitemid->lp_flags |= LP_DELETE;
SetBufferCommitInfoNeedsSave(buf);
}
if (sv_infomask != htup.t_data->t_infomask)
SetBufferCommitInfoNeedsSave(hbuffer);
LockBuffer(hbuffer, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(hbuffer);
}
}
/* htup null so no buffer to release */
}
/*