From 3afffbc902f16f5b9abd2464a2bbc17d9bc63316 Mon Sep 17 00:00:00 2001
From: Teodor Sigaev <teodor@sigaev.ru>
Date: Mon, 20 Oct 2008 16:35:14 +0000
Subject: [PATCH] Remove support of backward scan in GiST. Per discussion
http://archives.postgresql.org/pgsql-hackers/2008-10/msg00857.php
---
src/backend/access/gist/gistget.c | 40 ++++++++++++-------------------
1 file changed, 15 insertions(+), 25 deletions(-)
diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index a9a58455780..50d5fc21a47 100644
--- 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 1.77 2008/10/20 13:39:44 teodor Exp $
+ * $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.78 2008/10/20 16:35:14 teodor Exp $
*
*-------------------------------------------------------------------------
*/
@@ -23,9 +23,8 @@
#include "utils/memutils.h"
-static OffsetNumber gistfindnext(IndexScanDesc scan, OffsetNumber n,
- ScanDirection dir);
-static int64 gistnext(IndexScanDesc scan, ScanDirection dir, TIDBitmap *tbm);
+static OffsetNumber gistfindnext(IndexScanDesc scan, OffsetNumber n);
+static int64 gistnext(IndexScanDesc scan, TIDBitmap *tbm);
static bool gistindex_keytest(IndexTuple tuple, IndexScanDesc scan,
OffsetNumber offset);
@@ -80,6 +79,9 @@ gistgettuple(PG_FUNCTION_ARGS)
so = (GISTScanOpaque) scan->opaque;
+ if (dir != ForwardScanDirection)
+ elog(ERROR, "GiST doesn't support other scan directions than forward");
+
/*
* If we have produced an index tuple in the past and the executor has
* informed us we need to mark it as "killed", do so now.
@@ -90,7 +92,7 @@ gistgettuple(PG_FUNCTION_ARGS)
/*
* Get the next tuple that matches the search key.
*/
- res = (gistnext(scan, dir, NULL) > 0);
+ res = (gistnext(scan, NULL) > 0);
PG_RETURN_BOOL(res);
}
@@ -102,7 +104,7 @@ gistgetbitmap(PG_FUNCTION_ARGS)
TIDBitmap *tbm = (TIDBitmap *) PG_GETARG_POINTER(1);
int64 ntids;
- ntids = gistnext(scan, ForwardScanDirection, tbm);
+ ntids = gistnext(scan, tbm);
PG_RETURN_INT64(ntids);
}
@@ -122,7 +124,7 @@ gistgetbitmap(PG_FUNCTION_ARGS)
* non-killed tuple that matches the search key.
*/
static int64
-gistnext(IndexScanDesc scan, ScanDirection dir, TIDBitmap *tbm)
+gistnext(IndexScanDesc scan, TIDBitmap *tbm)
{
Page p;
OffsetNumber n;
@@ -169,9 +171,6 @@ gistnext(IndexScanDesc scan, ScanDirection dir, TIDBitmap *tbm)
if ( so->curPageData < so->nPageData )
{
- /*
- * pageData is already ordered for scan's direction
- */
scan->xs_ctup.t_self = so->pageData[ so->curPageData ].iptr;
scan->xs_recheck = so->pageData[ so->curPageData ].recheck;
so->curPageData ++;
@@ -252,17 +251,14 @@ gistnext(IndexScanDesc scan, ScanDirection dir, TIDBitmap *tbm)
continue;
}
- if (ScanDirectionIsBackward(dir))
- n = PageGetMaxOffsetNumber(p);
- else
- n = FirstOffsetNumber;
+ n = FirstOffsetNumber;
/* wonderful, we can look at page */
so->nPageData = so->curPageData = 0;
for (;;)
{
- n = gistfindnext(scan, n, dir);
+ n = gistfindnext(scan, n);
if (!OffsetNumberIsValid(n))
{
@@ -275,7 +271,7 @@ gistnext(IndexScanDesc scan, ScanDirection dir, TIDBitmap *tbm)
if ( !tbm && so->nPageData > 0 )
{
LockBuffer(so->curbuf, GIST_UNLOCK);
- return gistnext(scan, dir, NULL);
+ return gistnext(scan, NULL);
}
/*
@@ -346,10 +342,7 @@ gistnext(IndexScanDesc scan, ScanDirection dir, TIDBitmap *tbm)
so->stack->next = stk;
}
- if (ScanDirectionIsBackward(dir))
- n = OffsetNumberPrev(n);
- else
- n = OffsetNumberNext(n);
+ n = OffsetNumberNext(n);
}
}
@@ -475,7 +468,7 @@ gistindex_keytest(IndexTuple tuple,
* Page should be locked....
*/
static OffsetNumber
-gistfindnext(IndexScanDesc scan, OffsetNumber n, ScanDirection dir)
+gistfindnext(IndexScanDesc scan, OffsetNumber n)
{
OffsetNumber maxoff;
IndexTuple it;
@@ -500,10 +493,7 @@ gistfindnext(IndexScanDesc scan, OffsetNumber n, ScanDirection dir)
if (gistindex_keytest(it, scan, n))
break;
- if (ScanDirectionIsBackward(dir))
- n = OffsetNumberPrev(n);
- else
- n = OffsetNumberNext(n);
+ n = OffsetNumberNext(n);
}
MemoryContextSwitchTo(oldcxt);
--
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