Marginal hack to merge adjacent ReleaseBuffer/ReadBuffer calls into

ReleaseAndReadBuffer during GIST index searches.  We already did this
in btree and rtree, might as well do it here too.

diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index 70febc584c412afe8a5087bd9f4aff7a217ccb7e..03856874f33618fc88e173aa9e46dab9031ebb09 100644 (file)
--- a/src/backend/access/gist/gistget.c
+++ b/src/backend/access/gist/gistget.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.43 2004/12/31 21:59:10 pgsql Exp $
+ *   $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.44 2005/02/05 19:38:58 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -60,10 +60,11 @@ gistfirst(IndexScanDesc s, ScanDirection dir)
    BlockNumber blk;
    IndexTuple  it;
 
+   so = (GISTScanOpaque) s->opaque;
+
    b = ReadBuffer(s->indexRelation, GISTP_ROOT);
    p = BufferGetPage(b);
    po = (GISTPageOpaque) PageGetSpecialPointer(p);
-   so = (GISTScanOpaque) s->opaque;
 
    for (;;)
    {
@@ -75,12 +76,14 @@ gistfirst(IndexScanDesc s, ScanDirection dir)
 
        while (n < FirstOffsetNumber || n > maxoff)
        {
-           ReleaseBuffer(b);
-           if (so->s_stack == NULL)
+           stk = so->s_stack;
+           if (stk == NULL)
+           {
+               ReleaseBuffer(b);
                return false;
+           }
 
-           stk = so->s_stack;
-           b = ReadBuffer(s->indexRelation, stk->gs_blk);
+           b = ReleaseAndReadBuffer(b, s->indexRelation, stk->gs_blk);
            p = BufferGetPage(b);
            po = (GISTPageOpaque) PageGetSpecialPointer(p);
            maxoff = PageGetMaxOffsetNumber(p);
@@ -89,6 +92,7 @@ gistfirst(IndexScanDesc s, ScanDirection dir)
                n = OffsetNumberPrev(stk->gs_child);
            else
                n = OffsetNumberNext(stk->gs_child);
+
            so->s_stack = stk->gs_parent;
            pfree(stk);
 
@@ -116,8 +120,7 @@ gistfirst(IndexScanDesc s, ScanDirection dir)
            it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
            blk = ItemPointerGetBlockNumber(&(it->t_tid));
 
-           ReleaseBuffer(b);
-           b = ReadBuffer(s->indexRelation, blk);
+           b = ReleaseAndReadBuffer(b, s->indexRelation, blk);
            p = BufferGetPage(b);
            po = (GISTPageOpaque) PageGetSpecialPointer(p);
        }
@@ -137,6 +140,8 @@ gistnext(IndexScanDesc s, ScanDirection dir)
    BlockNumber blk;
    IndexTuple  it;
 
+   so = (GISTScanOpaque) s->opaque;
+
    blk = ItemPointerGetBlockNumber(&(s->currentItemData));
    n = ItemPointerGetOffsetNumber(&(s->currentItemData));
 
@@ -148,7 +153,6 @@ gistnext(IndexScanDesc s, ScanDirection dir)
    b = ReadBuffer(s->indexRelation, blk);
    p = BufferGetPage(b);
    po = (GISTPageOpaque) PageGetSpecialPointer(p);
-   so = (GISTScanOpaque) s->opaque;
 
    for (;;)
    {
@@ -157,20 +161,23 @@ gistnext(IndexScanDesc s, ScanDirection dir)
 
        while (n < FirstOffsetNumber || n > maxoff)
        {
-           ReleaseBuffer(b);
-           if (so->s_stack == NULL)
+           stk = so->s_stack;
+           if (stk == NULL)
+           {
+               ReleaseBuffer(b);
                return false;
+           }
 
-           stk = so->s_stack;
-           b = ReadBuffer(s->indexRelation, stk->gs_blk);
+           b = ReleaseAndReadBuffer(b, s->indexRelation, stk->gs_blk);
            p = BufferGetPage(b);
-           maxoff = PageGetMaxOffsetNumber(p);
            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);
 
@@ -198,8 +205,7 @@ gistnext(IndexScanDesc s, ScanDirection dir)
            it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
            blk = ItemPointerGetBlockNumber(&(it->t_tid));
 
-           ReleaseBuffer(b);
-           b = ReadBuffer(s->indexRelation, blk);
+           b = ReleaseAndReadBuffer(b, s->indexRelation, blk);
            p = BufferGetPage(b);
            po = (GISTPageOpaque) PageGetSpecialPointer(p);