Replace "amgetmulti" AM functions with "amgetbitmap", in which the whole

indexscan always occurs in one call, and the results are returned in a
TIDBitmap instead of a limited-size array of TIDs.  This should improve
speed a little by reducing AM entry/exit overhead, and it is necessary
infrastructure if we are ever to support bitmap indexes.

In an only slightly related change, add support for TIDBitmaps to preserve
(somewhat lossily) the knowledge that particular TIDs reported by an index
need to have their quals rechecked when the heap is visited.  This facility
is not really used yet; we'll need to extend the forced-recheck feature to
plain indexscans before it's useful, and that hasn't been coded yet.
The intent is to use it to clean up 8.3's horrid @@@ kluge for text search
with weighted queries.  There might be other uses in future, but that one
alone is sufficient reason.

Heikki Linnakangas, with some adjustments by me.

1 files changed, 32 insertions, 23 deletions

diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index 22a7d0ceae..4533ff8c85 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 1.69 2008/01/01 19:45:46 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.70 2008/04/10 22:25:25 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,13 +16,16 @@
 
 #include "access/gist_private.h"
 #include "executor/execdebug.h"
+#include "miscadmin.h"
 #include "pgstat.h"
 #include "utils/memutils.h"
 
 
 static OffsetNumber gistfindnext(IndexScanDesc scan, OffsetNumber n,
 			 ScanDirection dir);
-static int	gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids, int maxtids, bool ignore_killed_tuples);
+static int64 gistnext(IndexScanDesc scan, ScanDirection dir,
+					  ItemPointer tid, TIDBitmap *tbm,
+					  bool ignore_killed_tuples);
 static bool gistindex_keytest(IndexTuple tuple, IndexScanDesc scan,
 				  OffsetNumber offset);
 
@@ -114,32 +117,37 @@ gistgettuple(PG_FUNCTION_ARGS)
 	 * tuples, continue looping until we find a non-killed tuple that matches
 	 * the search key.
 	 */
-	res = (gistnext(scan, dir, &tid, 1, scan->ignore_killed_tuples)) ? true : false;
+	res = (gistnext(scan, dir, &tid, NULL, scan->ignore_killed_tuples) > 0) ? true : false;
 
 	PG_RETURN_BOOL(res);
 }
 
 Datum
-gistgetmulti(PG_FUNCTION_ARGS)
+gistgetbitmap(PG_FUNCTION_ARGS)
 {
 	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
-	ItemPointer tids = (ItemPointer) PG_GETARG_POINTER(1);
-	int32		max_tids = PG_GETARG_INT32(2);
-	int32	   *returned_tids = (int32 *) PG_GETARG_POINTER(3);
+	TIDBitmap *tbm = (TIDBitmap *) PG_GETARG_POINTER(1);
+	int64	   ntids;
 
-	*returned_tids = gistnext(scan, ForwardScanDirection, tids, max_tids, false);
+	ntids = gistnext(scan, ForwardScanDirection, NULL, tbm, false);
 
-	PG_RETURN_BOOL(*returned_tids == max_tids);
+	PG_RETURN_INT64(ntids);
 }
 
 /*
- * Fetch a tuples that matchs the search key; this can be invoked
- * either to fetch the first such tuple or subsequent matching
- * tuples. Returns true iff a matching tuple was found.
+ * Fetch tuple(s) that match the search key; this can be invoked
+ * either to fetch the first such tuple or subsequent matching tuples.
+ *
+ * This function is used by both gistgettuple and gistgetbitmap. When
+ * invoked from gistgettuple, tbm is null and the next matching tuple
+ * is returned in *tid. When invoked from getbitmap, tid is null and
+ * all matching tuples are added to tbm. In both cases, the function
+ * result is the number of returned tuples.
  */
-static int
-gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
-		 int maxtids, bool ignore_killed_tuples)
+static int64
+gistnext(IndexScanDesc scan, ScanDirection dir,
+		 ItemPointer tid, TIDBitmap *tbm,
+		 bool ignore_killed_tuples)
 {
 	Page		p;
 	OffsetNumber n;
@@ -148,7 +156,7 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
 	IndexTuple	it;
 	GISTPageOpaque opaque;
 	bool		resetoffset = false;
-	int			ntids = 0;
+	int64		ntids = 0;
 
 	so = (GISTScanOpaque) scan->opaque;
 
@@ -174,6 +182,8 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
 
 	for (;;)
 	{
+		CHECK_FOR_INTERRUPTS();
+
 		/* First of all, we need lock buffer */
 		Assert(so->curbuf != InvalidBuffer);
 		LockBuffer(so->curbuf, GIST_SHARE);
@@ -285,20 +295,21 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
 				 * return success. Note that we keep "curbuf" pinned so that
 				 * we can efficiently resume the index scan later.
 				 */
-
 				ItemPointerSet(&(so->curpos),
 							   BufferGetBlockNumber(so->curbuf), n);
 
 				if (!(ignore_killed_tuples && ItemIdIsDead(PageGetItemId(p, n))))
 				{
 					it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
-					tids[ntids] = scan->xs_ctup.t_self = it->t_tid;
 					ntids++;
-
-					if (ntids == maxtids)
+					if (tbm != NULL)
+						tbm_add_tuples(tbm, &it->t_tid, 1, false);
+					else 
 					{
+						*tid = scan->xs_ctup.t_self = it->t_tid;
+
 						LockBuffer(so->curbuf, GIST_UNLOCK);
-						return ntids;
+						return ntids; /* always 1 */
 					}
 				}
 			}
@@ -308,7 +319,6 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
 				 * We've found an entry in an internal node whose key is
 				 * consistent with the search key, so push it to stack
 				 */
-
 				stk = (GISTSearchStack *) palloc(sizeof(GISTSearchStack));
 
 				it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
@@ -318,7 +328,6 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
 
 				stk->next = so->stack->next;
 				so->stack->next = stk;
-
 			}
 
 			if (ScanDirectionIsBackward(dir))