Phase 2 of project to make index operator lossiness be determined at runtime

instead of plan time.  Extend the amgettuple API so that the index AM returns
a boolean indicating whether the indexquals need to be rechecked, and make
that rechecking happen in nodeIndexscan.c (currently the only place where
it's expected to be needed; other callers of index_getnext are just erroring
out for now).  For the moment, GIN and GIST have stub logic that just always
sets the recheck flag to TRUE --- I'm hoping to get Teodor to handle pushing
that control down to the opclass consistent() functions.  The planner no
longer pays any attention to amopreqcheck, and that catalog column will go
away in due course.

1 files changed, 22 insertions, 20 deletions

diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index 4533ff8c85f..8e921395825 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 1.70 2008/04/10 22:25:25 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.71 2008/04/13 19:18:14 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -23,9 +23,7 @@
 
 static OffsetNumber gistfindnext(IndexScanDesc scan, OffsetNumber n,
 			 ScanDirection dir);
-static int64 gistnext(IndexScanDesc scan, ScanDirection dir,
-					  ItemPointer tid, TIDBitmap *tbm,
-					  bool ignore_killed_tuples);
+static int64 gistnext(IndexScanDesc scan, ScanDirection dir, TIDBitmap *tbm);
 static bool gistindex_keytest(IndexTuple tuple, IndexScanDesc scan,
 				  OffsetNumber offset);
 
@@ -100,7 +98,6 @@ gistgettuple(PG_FUNCTION_ARGS)
 	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
 	ScanDirection dir = (ScanDirection) PG_GETARG_INT32(1);
 	GISTScanOpaque so;
-	ItemPointerData tid;
 	bool		res;
 
 	so = (GISTScanOpaque) scan->opaque;
@@ -113,11 +110,9 @@ gistgettuple(PG_FUNCTION_ARGS)
 		killtuple(scan->indexRelation, so, &(so->curpos));
 
 	/*
-	 * Get the next tuple that matches the search key. If asked to skip killed
-	 * tuples, continue looping until we find a non-killed tuple that matches
-	 * the search key.
+	 * Get the next tuple that matches the search key.
 	 */
-	res = (gistnext(scan, dir, &tid, NULL, scan->ignore_killed_tuples) > 0) ? true : false;
+	res = (gistnext(scan, dir, NULL) > 0);
 
 	PG_RETURN_BOOL(res);
 }
@@ -129,7 +124,7 @@ gistgetbitmap(PG_FUNCTION_ARGS)
 	TIDBitmap *tbm = (TIDBitmap *) PG_GETARG_POINTER(1);
 	int64	   ntids;
 
-	ntids = gistnext(scan, ForwardScanDirection, NULL, tbm, false);
+	ntids = gistnext(scan, ForwardScanDirection, tbm);
 
 	PG_RETURN_INT64(ntids);
 }
@@ -140,20 +135,23 @@ gistgetbitmap(PG_FUNCTION_ARGS)
  *
  * 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.
+ * is returned in scan->xs_ctup.t_self.  When invoked from getbitmap,
+ * tbm is non-null and all matching tuples are added to tbm before
+ * returning.  In both cases, the function result is the number of
+ * returned tuples.
+ *
+ * If scan specifies to skip killed tuples, continue looping until we find a
+ * non-killed tuple that matches the search key.
  */
 static int64
-gistnext(IndexScanDesc scan, ScanDirection dir,
-		 ItemPointer tid, TIDBitmap *tbm,
-		 bool ignore_killed_tuples)
+gistnext(IndexScanDesc scan, ScanDirection dir, TIDBitmap *tbm)
 {
 	Page		p;
 	OffsetNumber n;
 	GISTScanOpaque so;
 	GISTSearchStack *stk;
 	IndexTuple	it;
+	bool		recheck;
 	GISTPageOpaque opaque;
 	bool		resetoffset = false;
 	int64		ntids = 0;
@@ -194,7 +192,7 @@ gistnext(IndexScanDesc scan, ScanDirection dir,
 
 		if (XLogRecPtrIsInvalid(so->stack->lsn) || !XLByteEQ(so->stack->lsn, PageGetLSN(p)))
 		{
-			/* page changed from last visit or visit first time , reset offset */
+			/* first visit or page changed from last visit, reset offset */
 			so->stack->lsn = PageGetLSN(p);
 			resetoffset = true;
 
@@ -259,6 +257,8 @@ gistnext(IndexScanDesc scan, ScanDirection dir,
 		for (;;)
 		{
 			n = gistfindnext(scan, n, dir);
+			/* XXX for the moment, treat all GIST operators as lossy */
+			recheck = true;
 
 			if (!OffsetNumberIsValid(n))
 			{
@@ -298,15 +298,17 @@ gistnext(IndexScanDesc scan, ScanDirection dir,
 				ItemPointerSet(&(so->curpos),
 							   BufferGetBlockNumber(so->curbuf), n);
 
-				if (!(ignore_killed_tuples && ItemIdIsDead(PageGetItemId(p, n))))
+				if (!(scan->ignore_killed_tuples &&
+					  ItemIdIsDead(PageGetItemId(p, n))))
 				{
 					it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
 					ntids++;
 					if (tbm != NULL)
-						tbm_add_tuples(tbm, &it->t_tid, 1, false);
+						tbm_add_tuples(tbm, &it->t_tid, 1, recheck);
 					else 
 					{
-						*tid = scan->xs_ctup.t_self = it->t_tid;
+						scan->xs_ctup.t_self = it->t_tid;
+						scan->xs_recheck = recheck;
 
 						LockBuffer(so->curbuf, GIST_UNLOCK);
 						return ntids; /* always 1 */