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Tweak indexscan and seqscan code to arrange that steps from one page to

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the next are handled by ReleaseAndReadBuffer rather than separate
ReleaseBuffer and ReadBuffer calls.  This cuts the number of acquisitions
of the BufMgrLock by a factor of 2 (possibly more, if an indexscan happens
to pull successive rows from the same heap page).  Unfortunately this
doesn't seem enough to get us out of the recently discussed context-switch
storm problem, but it's surely worth doing anyway.
This commit is contained in:
Tom Lane
2004-04-21 18:24:26 +00:00
parent 95a03e9cdf
commit 37fa3b6c89
11 changed files with 132 additions and 65 deletions
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12
src/backend/access/nbtree/nbtinsert.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.111 2004/01/07 18:56:24 neilc Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.112 2004/04/21 18:24:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -297,9 +297,7 @@ _bt_check_unique(Relation rel, BTItem btitem, Relation heapRel,
for (;;)
{
nblkno = opaque->btpo_next;
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
nbuf = _bt_getbuf(rel, nblkno, BT_READ);
nbuf = _bt_relandgetbuf(rel, nbuf, nblkno, BT_READ);
page = BufferGetPage(nbuf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
if (!P_IGNORE(opaque))
@@ -454,9 +452,7 @@ _bt_insertonpg(Relation rel,
{
BlockNumber rblkno = lpageop->btpo_next;
if (rbuf != InvalidBuffer)
_bt_relbuf(rel, rbuf);
rbuf = _bt_getbuf(rel, rblkno, BT_WRITE);
rbuf = _bt_relandgetbuf(rel, rbuf, rblkno, BT_WRITE);
page = BufferGetPage(rbuf);
lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
if (!P_IGNORE(lpageop))
@@ -1357,7 +1353,7 @@ _bt_getstackbuf(Relation rel, BTStack stack, int access)
if (P_RIGHTMOST(opaque))
{
_bt_relbuf(rel, buf);
return (InvalidBuffer);
return InvalidBuffer;
}
blkno = opaque->btpo_next;
start = InvalidOffsetNumber;