Marinos Yannikos <[EMAIL PROTECTED]> writes:
> Some more things I tried:
You might try the attached patch (which I just applied to HEAD).
It cuts down the number of acquisitions of the BufMgrLock by merging
adjacent bufmgr calls during a GIST index search. I'm not hugely
hopeful that this will help, since I did something similar to btree
last spring without much improvement for context swap storms involving
btree searches ... but it seems worth trying.
regards, tom lane
*** src/backend/access/gist/gistget.c.orig Fri Dec 31 17:45:27 2004
--- src/backend/access/gist/gistget.c Sat Feb 5 14:19:52 2005
***************
*** 60,69 ****
BlockNumber blk;
IndexTuple it;
b = ReadBuffer(s->indexRelation, GISTP_ROOT);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
- so = (GISTScanOpaque) s->opaque;
for (;;)
{
--- 60,70 ----
BlockNumber blk;
IndexTuple it;
+ so = (GISTScanOpaque) s->opaque;
+
b = ReadBuffer(s->indexRelation, GISTP_ROOT);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
for (;;)
{
***************
*** 75,86 ****
while (n < FirstOffsetNumber || n > maxoff)
{
! ReleaseBuffer(b);
! if (so->s_stack == NULL)
return false;
! stk = so->s_stack;
! b = ReadBuffer(s->indexRelation, stk->gs_blk);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
maxoff = PageGetMaxOffsetNumber(p);
--- 76,89 ----
while (n < FirstOffsetNumber || n > maxoff)
{
! stk = so->s_stack;
! if (stk == NULL)
! {
! ReleaseBuffer(b);
return false;
+ }
! b = ReleaseAndReadBuffer(b, s->indexRelation,
stk->gs_blk);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
maxoff = PageGetMaxOffsetNumber(p);
***************
*** 89,94 ****
--- 92,98 ----
n = OffsetNumberPrev(stk->gs_child);
else
n = OffsetNumberNext(stk->gs_child);
+
so->s_stack = stk->gs_parent;
pfree(stk);
***************
*** 116,123 ****
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
blk = ItemPointerGetBlockNumber(&(it->t_tid));
! ReleaseBuffer(b);
! b = ReadBuffer(s->indexRelation, blk);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
}
--- 120,126 ----
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
blk = ItemPointerGetBlockNumber(&(it->t_tid));
! b = ReleaseAndReadBuffer(b, s->indexRelation, blk);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
}
***************
*** 137,142 ****
--- 140,147 ----
BlockNumber blk;
IndexTuple it;
+ so = (GISTScanOpaque) s->opaque;
+
blk = ItemPointerGetBlockNumber(&(s->currentItemData));
n = ItemPointerGetOffsetNumber(&(s->currentItemData));
***************
*** 148,154 ****
b = ReadBuffer(s->indexRelation, blk);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
- so = (GISTScanOpaque) s->opaque;
for (;;)
{
--- 153,158 ----
***************
*** 157,176 ****
while (n < FirstOffsetNumber || n > maxoff)
{
! ReleaseBuffer(b);
! if (so->s_stack == NULL)
return false;
! stk = so->s_stack;
! b = ReadBuffer(s->indexRelation, stk->gs_blk);
p = BufferGetPage(b);
- maxoff = PageGetMaxOffsetNumber(p);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
if (ScanDirectionIsBackward(dir))
n = OffsetNumberPrev(stk->gs_child);
else
n = OffsetNumberNext(stk->gs_child);
so->s_stack = stk->gs_parent;
pfree(stk);
--- 161,183 ----
while (n < FirstOffsetNumber || n > maxoff)
{
! stk = so->s_stack;
! if (stk == NULL)
! {
! ReleaseBuffer(b);
return false;
+ }
! b = ReleaseAndReadBuffer(b, s->indexRelation,
stk->gs_blk);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
+ maxoff = PageGetMaxOffsetNumber(p);
if (ScanDirectionIsBackward(dir))
n = OffsetNumberPrev(stk->gs_child);
else
n = OffsetNumberNext(stk->gs_child);
+
so->s_stack = stk->gs_parent;
pfree(stk);
***************
*** 198,205 ****
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
blk = ItemPointerGetBlockNumber(&(it->t_tid));
! ReleaseBuffer(b);
! b = ReadBuffer(s->indexRelation, blk);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
--- 205,211 ----
it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
blk = ItemPointerGetBlockNumber(&(it->t_tid));
! b = ReleaseAndReadBuffer(b, s->indexRelation, blk);
p = BufferGetPage(b);
po = (GISTPageOpaque) PageGetSpecialPointer(p);
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