From 67e378316a9336f85d982f93dd8ddf7234dfeabb Mon Sep 17 00:00:00 2001
From: "Paul A. Jungwirth" <pj@illuminatedcomputing.com>
Date: Thu, 13 Nov 2025 16:45:40 -0800
Subject: [PATCH v1] Improve comment and error handling in
 GetOperatorFromCompareType

Despite the comment, we always ereport if we don't find a strategy number.

Also we should avoid using uninitialized opfamily and opcintype values to build
error messages. If get_opclass_opfamily_and_input_type fails, something is very
wrong, since get_opclass_method just succeeded. Let's just fail. That reduces
the paths through the function too, so reasoning is easier. I also inverted the
conditional to reduce nesting.
---
 src/backend/commands/indexcmds.c | 49 +++++++++++++++++---------------
 1 file changed, 26 insertions(+), 23 deletions(-)

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 5712fac3697..0298d6268db 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -2439,8 +2439,7 @@ GetDefaultOpClass(Oid type_id, Oid am_id)
  * Finds an operator from a CompareType.  This is used for temporal index
  * constraints (and other temporal features) to look up equality and overlaps
  * operators.  We ask an opclass support function to translate from the
- * compare type to the internal strategy numbers.  If the function isn't
- * defined or it gives no result, we set *strat to InvalidStrategy.
+ * compare type to the internal strategy numbers.
  */
 void
 GetOperatorFromCompareType(Oid opclass, Oid rhstype, CompareType cmptype,
@@ -2456,30 +2455,34 @@ GetOperatorFromCompareType(Oid opclass, Oid rhstype, CompareType cmptype,
 
 	*opid = InvalidOid;
 
-	if (get_opclass_opfamily_and_input_type(opclass, &opfamily, &opcintype))
-	{
+	if (!get_opclass_opfamily_and_input_type(opclass, &opfamily, &opcintype))
 		/*
-		 * Ask the index AM to translate to its internal stratnum
+		 * Since get_opclass_method succeeded, we shouldn't ever fail here.
+		 * If it happens, don't proceed, since opfamily and opcintype are uninitialized.
 		 */
-		*strat = IndexAmTranslateCompareType(cmptype, amid, opfamily, true);
-		if (*strat == InvalidStrategy)
-			ereport(ERROR,
-					errcode(ERRCODE_UNDEFINED_OBJECT),
-					cmptype == COMPARE_EQ ? errmsg("could not identify an equality operator for type %s", format_type_be(opcintype)) :
-					cmptype == COMPARE_OVERLAP ? errmsg("could not identify an overlaps operator for type %s", format_type_be(opcintype)) :
-					cmptype == COMPARE_CONTAINED_BY ? errmsg("could not identify a contained-by operator for type %s", format_type_be(opcintype)) : 0,
-					errdetail("Could not translate compare type %d for operator family \"%s\" of access method \"%s\".",
-							  cmptype, get_opfamily_name(opfamily, false), get_am_name(amid)));
+		elog(ERROR, "cache lookup failed for opclass %u", opclass);
 
-		/*
-		 * We parameterize rhstype so foreign keys can ask for a <@ operator
-		 * whose rhs matches the aggregate function. For example range_agg
-		 * returns anymultirange.
-		 */
-		if (!OidIsValid(rhstype))
-			rhstype = opcintype;
-		*opid = get_opfamily_member(opfamily, opcintype, rhstype, *strat);
-	}
+	/*
+	 * Ask the index AM to translate to its internal stratnum
+	 */
+	*strat = IndexAmTranslateCompareType(cmptype, amid, opfamily, true);
+	if (*strat == InvalidStrategy)
+		ereport(ERROR,
+				errcode(ERRCODE_UNDEFINED_OBJECT),
+				cmptype == COMPARE_EQ ? errmsg("could not identify an equality operator for type %s", format_type_be(opcintype)) :
+				cmptype == COMPARE_OVERLAP ? errmsg("could not identify an overlaps operator for type %s", format_type_be(opcintype)) :
+				cmptype == COMPARE_CONTAINED_BY ? errmsg("could not identify a contained-by operator for type %s", format_type_be(opcintype)) : 0,
+				errdetail("Could not translate compare type %d for operator family \"%s\" of access method \"%s\".",
+						  cmptype, get_opfamily_name(opfamily, false), get_am_name(amid)));
+
+	/*
+	 * We parameterize rhstype so foreign keys can ask for a <@ operator
+	 * whose rhs matches the aggregate function. For example range_agg
+	 * returns anymultirange.
+	 */
+	if (!OidIsValid(rhstype))
+		rhstype = opcintype;
+	*opid = get_opfamily_member(opfamily, opcintype, rhstype, *strat);
 
 	if (!OidIsValid(*opid))
 		ereport(ERROR,
-- 
2.45.0