Don't require sort support functions to provide a comparator.

This could be useful for datatypes like text, where we might want
to optimize for some collations but not others.  However, this patch
doesn't introduce any new sortsupport functions that work this way;
it merely revises the code so that future patches may do so.

Patch by me.  Review by Peter Geoghegan.

1 files changed, 0 insertions, 56 deletions

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 4b5ef99531b..552e498cf57 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -246,62 +246,6 @@ get_ordering_op_properties(Oid opno,
 }
 
 /*
- * get_sort_function_for_ordering_op
- *		Get the OID of the datatype-specific btree sort support function,
- *		or if there is none, the btree comparison function,
- *		associated with an ordering operator (a "<" or ">" operator).
- *
- * *sortfunc receives the support or comparison function OID.
- * *issupport is set TRUE if it's a support func, FALSE if a comparison func.
- * *reverse is set FALSE if the operator is "<", TRUE if it's ">"
- * (indicating that comparison results must be negated before use).
- *
- * Returns TRUE if successful, FALSE if no btree function can be found.
- * (This indicates that the operator is not a valid ordering operator.)
- */
-bool
-get_sort_function_for_ordering_op(Oid opno, Oid *sortfunc,
-								  bool *issupport, bool *reverse)
-{
-	Oid			opfamily;
-	Oid			opcintype;
-	int16		strategy;
-
-	/* Find the operator in pg_amop */
-	if (get_ordering_op_properties(opno,
-								   &opfamily, &opcintype, &strategy))
-	{
-		/* Found a suitable opfamily, get matching support function */
-		*sortfunc = get_opfamily_proc(opfamily,
-									  opcintype,
-									  opcintype,
-									  BTSORTSUPPORT_PROC);
-		if (OidIsValid(*sortfunc))
-			*issupport = true;
-		else
-		{
-			/* opfamily doesn't provide sort support, get comparison func */
-			*sortfunc = get_opfamily_proc(opfamily,
-										  opcintype,
-										  opcintype,
-										  BTORDER_PROC);
-			if (!OidIsValid(*sortfunc)) /* should not happen */
-				elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
-					 BTORDER_PROC, opcintype, opcintype, opfamily);
-			*issupport = false;
-		}
-		*reverse = (strategy == BTGreaterStrategyNumber);
-		return true;
-	}
-
-	/* ensure outputs are set on failure */
-	*sortfunc = InvalidOid;
-	*issupport = false;
-	*reverse = false;
-	return false;
-}
-
-/*
  * get_equality_op_for_ordering_op
  *		Get the OID of the datatype-specific btree equality operator
  *		associated with an ordering operator (a "<" or ">" operator).