Remove support of backward scan in GiST. Per discussion

http://archives.postgresql.org/pgsql-hackers/2008-10/msg00857.php

diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index a9a5845..50d5fc2 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 1.77 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);