Fix order of parameters in BRIN minmax-multi calls

tvondra · tvondra · commit 1dad2a5ea3d1 · 2021-04-04T19:25:41.000+02:00
The BRIN minmax-multi consistent function incorrectly assumed it can lookup an operator, and then swap the arguments to get the commutator. For example <(a,b) would be called as <(b,a) to get >(a,b). This works when the arguments are of the same type, but with cross-type opclasses this fails. We can't swap <(float4,float8) arguments, for example. Fixed by passing arguments in the right order. Discussion: https://postgr.es/m/CAJKUy5jLZFLCxyxfT%3DMfK5mtPfSzHA1rVLowR-j4RRsFVvKm7A%40mail.gmail.com
diff --git a/src/backend/access/brin/brin_minmax_multi.c b/src/backend/access/brin/brin_minmax_multi.c
@@ -2606,16 +2606,16 @@ brin_minmax_multi_consistent(PG_FUNCTION_ARGS)
 						 * value in the array.
 						 */
 						cmpFn = minmax_multi_get_strategy_procinfo(bdesc, attno, subtype,
-																   BTLessStrategyNumber);
-						compar = FunctionCall2Coll(cmpFn, colloid, value, minval);
+																   BTGreaterStrategyNumber);
+						compar = FunctionCall2Coll(cmpFn, colloid, minval, value);
 
 						/* smaller than the smallest value in this range */
 						if (DatumGetBool(compar))
 							break;
 
 						cmpFn = minmax_multi_get_strategy_procinfo(bdesc, attno, subtype,
-																   BTGreaterStrategyNumber);
-						compar = FunctionCall2Coll(cmpFn, colloid, value, maxval);
+																   BTLessStrategyNumber);
+						compar = FunctionCall2Coll(cmpFn, colloid, maxval, value);
 
 						/* larger than the largest value in this range */
 						if (DatumGetBool(compar))
