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.

3 files changed, 28 insertions, 14 deletions

diff --git a/src/backend/utils/adt/tsginidx.c b/src/backend/utils/adt/tsginidx.c
index add1fc1910c..55518834ae9 100644
--- a/src/backend/utils/adt/tsginidx.c
+++ b/src/backend/utils/adt/tsginidx.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsginidx.c,v 1.10 2008/03/25 22:42:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsginidx.c,v 1.11 2008/04/14 17:05:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -54,7 +54,7 @@ gin_extract_tsquery(PG_FUNCTION_ARGS)
 {
 	TSQuery		query = PG_GETARG_TSQUERY(0);
 	int32	   *nentries = (int32 *) PG_GETARG_POINTER(1);
-	StrategyNumber strategy = PG_GETARG_UINT16(2);
+	/* StrategyNumber strategy = PG_GETARG_UINT16(2); */
 	Datum	   *entries = NULL;
 
 	*nentries = 0;
@@ -89,12 +89,6 @@ gin_extract_tsquery(PG_FUNCTION_ARGS)
 				txt = cstring_to_text_with_len(GETOPERAND(query) + val->distance,
 											   val->length);
 				entries[j++] = PointerGetDatum(txt);
-
-				if (strategy != TSearchWithClassStrategyNumber && val->weight != 0)
-					ereport(ERROR,
-							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							 errmsg("@@ operator does not support lexeme weight restrictions in GIN index searches"),
-							 errhint("Use the @@@ operator instead.")));
 			}
 	}
 	else
@@ -109,6 +103,7 @@ typedef struct
 {
 	QueryItem  *frst;
 	bool	   *mapped_check;
+	bool	   *need_recheck;
 } GinChkVal;
 
 static bool
@@ -116,6 +111,10 @@ checkcondition_gin(void *checkval, QueryOperand *val)
 {
 	GinChkVal  *gcv = (GinChkVal *) checkval;
 
+	/* if any val requiring a weight is used, set recheck flag */
+	if (val->weight != 0)
+		*(gcv->need_recheck) = true;
+
 	return gcv->mapped_check[((QueryItem *) val) - gcv->frst];
 }
 
@@ -125,8 +124,12 @@ gin_tsquery_consistent(PG_FUNCTION_ARGS)
 	bool	   *check = (bool *) PG_GETARG_POINTER(0);
 	/* StrategyNumber strategy = PG_GETARG_UINT16(1); */
 	TSQuery		query = PG_GETARG_TSQUERY(2);
+	bool	   *recheck = (bool *) PG_GETARG_POINTER(3);
 	bool		res = FALSE;
 
+	/* The query requires recheck only if it involves weights */
+	*recheck = false;
+
 	if (query->size > 0)
 	{
 		int			i,
@@ -144,6 +147,7 @@ gin_tsquery_consistent(PG_FUNCTION_ARGS)
 
 		gcv.frst = item = GETQUERY(query);
 		gcv.mapped_check = (bool *) palloc(sizeof(bool) * query->size);
+		gcv.need_recheck = recheck;
 
 		for (i = 0; i < query->size; i++)
 			if (item[i].type == QI_VAL)
diff --git a/src/backend/utils/adt/tsgistidx.c b/src/backend/utils/adt/tsgistidx.c
index f3a98ba6f8d..ecbac7b40f2 100644
--- a/src/backend/utils/adt/tsgistidx.c
+++ b/src/backend/utils/adt/tsgistidx.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsgistidx.c,v 1.7 2008/01/01 19:45:52 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsgistidx.c,v 1.8 2008/04/14 17:05:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -330,10 +330,15 @@ checkcondition_bit(void *checkval, QueryOperand *val)
 Datum
 gtsvector_consistent(PG_FUNCTION_ARGS)
 {
+	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
 	TSQuery		query = PG_GETARG_TSQUERY(1);
-	SignTSVector *key = (SignTSVector *) DatumGetPointer(
-									((GISTENTRY *) PG_GETARG_POINTER(0))->key
-	);
+	/* StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(2); */
+	/* Oid		subtype = PG_GETARG_OID(3); */
+	bool	   *recheck = (bool *) PG_GETARG_POINTER(4);
+	SignTSVector *key = (SignTSVector *) DatumGetPointer(entry->key);
+
+	/* All cases served by this function are inexact */
+	*recheck = true;
 
 	if (!query->size)
 		PG_RETURN_BOOL(false);
diff --git a/src/backend/utils/adt/tsquery_gist.c b/src/backend/utils/adt/tsquery_gist.c
index fdefd92bae2..df813b59223 100644
--- a/src/backend/utils/adt/tsquery_gist.c
+++ b/src/backend/utils/adt/tsquery_gist.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsquery_gist.c,v 1.4 2008/01/01 19:45:53 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsquery_gist.c,v 1.5 2008/04/14 17:05:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -52,12 +52,17 @@ Datum
 gtsquery_consistent(PG_FUNCTION_ARGS)
 {
 	GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
-	TSQuerySign *key = (TSQuerySign *) DatumGetPointer(entry->key);
 	TSQuery		query = PG_GETARG_TSQUERY(1);
 	StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(2);
+	/* Oid		subtype = PG_GETARG_OID(3); */
+	bool	   *recheck = (bool *) PG_GETARG_POINTER(4);
+	TSQuerySign *key = (TSQuerySign *) DatumGetPointer(entry->key);
 	TSQuerySign sq = makeTSQuerySign(query);
 	bool		retval;
 
+	/* All cases served by this function are inexact */
+	*recheck = true;
+
 	switch (strategy)
 	{
 		case RTContainsStrategyNumber: