Push index operator lossiness determination down to GIST/GIN opclass

"consistent" functions, and remove pg_amop.opreqcheck, as per recent
discussion.  The main immediate benefit of this is that we no longer need
8.3's ugly hack of requiring @@@ rather than @@ to test weight-using tsquery
searches on GIN indexes.  In future it should be possible to optimize some
other queries better than is done now, by detecting at runtime whether the
index match is exact or not.

Tom Lane, after an idea of Heikki's, and with some help from Teodor.

1 files changed, 34 insertions, 7 deletions

diff --git a/src/backend/access/gin/ginarrayproc.c b/src/backend/access/gin/ginarrayproc.c
index c453cda525c..c85399d632f 100644
--- a/src/backend/access/gin/ginarrayproc.c
+++ b/src/backend/access/gin/ginarrayproc.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/gin/ginarrayproc.c,v 1.12 2008/01/01 19:45:46 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/gin/ginarrayproc.c,v 1.13 2008/04/14 17:05:33 tgl Exp $
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
@@ -95,8 +95,9 @@ ginarrayconsistent(PG_FUNCTION_ARGS)
 	bool	   *check = (bool *) PG_GETARG_POINTER(0);
 	StrategyNumber strategy = PG_GETARG_UINT16(1);
 	ArrayType  *query = PG_GETARG_ARRAYTYPE_P(2);
-	int			res,
-				i,
+	bool	   *recheck = (bool *) PG_GETARG_POINTER(3);
+	bool		res;
+	int			i,
 				nentries;
 
 	/* ARRAYCHECK was already done by previous ginarrayextract call */
@@ -104,25 +105,51 @@ ginarrayconsistent(PG_FUNCTION_ARGS)
 	switch (strategy)
 	{
 		case GinOverlapStrategy:
+			/* result is not lossy */
+			*recheck = false;
+			/* at least one element in check[] is true, so result = true */
+			res = true;
+			break;
 		case GinContainedStrategy:
+			/* we will need recheck */
+			*recheck = true;
 			/* at least one element in check[] is true, so result = true */
-			res = TRUE;
+			res = true;
 			break;
 		case GinContainsStrategy:
+			/* result is not lossy */
+			*recheck = false;
+			/* must have all elements in check[] true */
+			nentries = ArrayGetNItems(ARR_NDIM(query), ARR_DIMS(query));
+			res = true;
+			for (i = 0; i < nentries; i++)
+			{
+				if (!check[i])
+				{
+					res = false;
+					break;
+				}
+			}
+			break;
 		case GinEqualStrategy:
+			/* we will need recheck */
+			*recheck = true;
+			/* must have all elements in check[] true */
 			nentries = ArrayGetNItems(ARR_NDIM(query), ARR_DIMS(query));
-			res = TRUE;
+			res = true;
 			for (i = 0; i < nentries; i++)
+			{
 				if (!check[i])
 				{
-					res = FALSE;
+					res = false;
 					break;
 				}
+			}
 			break;
 		default:
 			elog(ERROR, "ginarrayconsistent: unknown strategy number: %d",
 				 strategy);
-			res = FALSE;
+			res = false;
 	}
 
 	PG_RETURN_BOOL(res);