Replace get_equal_strategy_number_for_am() by get_equal_strategy_number()

get_equal_strategy_number_for_am() gets the equal strategy number for
an AM.  This currently only supports btree and hash.  In the more
general case, this also depends on the operator class (see for example
GistTranslateStratnum()).  To support that, replace this function with
get_equal_strategy_number() that takes an opclass and derives it from
there.  (This function already existed before as a static function, so
the signature is kept for simplicity.)

This patch is only a refactoring, it doesn't add support for other
index AMs such as gist.  This will be done separately.

Reviewed-by: Paul Jungwirth <pj@illuminatedcomputing.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com

Author: petere

src/backend/executor/execReplication.c

@@ -39,16 +39,17 @@ static bool tuples_equal(TupleTableSlot *slot1, TupleTableSlot *slot2,
 
 /*
  * Returns the fixed strategy number, if any, of the equality operator for the
- * given index access method, otherwise, InvalidStrategy.
+ * given operator class, otherwise, InvalidStrategy.
  *
  * Currently, only Btree and Hash indexes are supported. The other index access
  * methods don't have a fixed strategy for equality operation - instead, the
  * support routines of each operator class interpret the strategy numbers
  * according to the operator class's definition.
  */
 StrategyNumber
-get_equal_strategy_number_for_am(Oid am)
+get_equal_strategy_number(Oid opclass)
 {
+	Oid			am = get_opclass_method(opclass);
 	int			ret;
 
 	switch (am)
@@ -68,18 +69,6 @@ get_equal_strategy_number_for_am(Oid am)
 	return ret;
 }
 
-/*
- * Return the appropriate strategy number which corresponds to the equality
- * operator.
- */
-static StrategyNumber
-get_equal_strategy_number(Oid opclass)
-{
-	Oid			am = get_opclass_method(opclass);
-
-	return get_equal_strategy_number_for_am(am);
-}
-
 /*
  * Setup a ScanKey for a search in the relation 'rel' for a tuple 'key' that
  * is setup to match 'rel' (*NOT* idxrel!).

src/backend/replication/logical/relation.c

@@ -29,6 +29,7 @@
 #include "replication/logicalrelation.h"
 #include "replication/worker_internal.h"
 #include "utils/inval.h"
+#include "utils/syscache.h"
 
 
 static MemoryContext LogicalRepRelMapContext = NULL;
@@ -815,7 +816,7 @@ FindUsableIndexForReplicaIdentityFull(Relation localrel, AttrMap *attrmap)
  * The reasons why only Btree and Hash indexes can be considered as usable are:
  *
  * 1) Other index access methods don't have a fixed strategy for equality
- * operation. Refer get_equal_strategy_number_for_am().
+ * operation. Refer get_equal_strategy_number().
  *
  * 2) For indexes other than PK and REPLICA IDENTITY, we need to match the
  * local and remote tuples. The equality routine tuples_equal() cannot accept
@@ -833,17 +834,25 @@ bool
 IsIndexUsableForReplicaIdentityFull(Relation idxrel, AttrMap *attrmap)
 {
 	AttrNumber	keycol;
-
-	/* Ensure that the index access method has a valid equal strategy */
-	if (get_equal_strategy_number_for_am(idxrel->rd_rel->relam) == InvalidStrategy)
-		return false;
+	oidvector  *indclass;
 
 	/* The index must not be a partial index */
 	if (!heap_attisnull(idxrel->rd_indextuple, Anum_pg_index_indpred, NULL))
 		return false;
 
 	Assert(idxrel->rd_index->indnatts >= 1);
 
+	indclass = (oidvector *) DatumGetPointer(SysCacheGetAttrNotNull(INDEXRELID,
+																	idxrel->rd_indextuple,
+																	Anum_pg_index_indclass));
+
+	/* Ensure that the index has a valid equal strategy for each key column */
+	for (int i = 0; i < idxrel->rd_index->indnkeyatts; i++)
+	{
+		if (get_equal_strategy_number(indclass->values[i]) == InvalidStrategy)
+			return false;
+	}
+
 	/* The leftmost index field must not be an expression */
 	keycol = idxrel->rd_index->indkey.values[0];
 	if (!AttributeNumberIsValid(keycol))

src/include/executor/executor.h

@@ -657,7 +657,7 @@ extern void check_exclusion_constraint(Relation heap, Relation index,
 /*
  * prototypes from functions in execReplication.c
  */
-extern StrategyNumber get_equal_strategy_number_for_am(Oid am);
+extern StrategyNumber get_equal_strategy_number(Oid opclass);
 extern bool RelationFindReplTupleByIndex(Relation rel, Oid idxoid,
 										 LockTupleMode lockmode,
 										 TupleTableSlot *searchslot,