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 a9a58455780f2c75238ab76f1434a27946a57d23..50d5fc21a47acdf97c0087f888aa2a2bb7b85222 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);