Create CanPushdownSubqery wrapper for better readability (#4108)

src/backend/distributed/planner/multi_logical_planner.c

@@ -1104,7 +1104,7 @@ ErrorHintRequired(const char *errorHint, Query *queryTree)
 
 
 /*
- * DeferErrorIfSubqueryNotSupported checks that we can perform distributed planning for
+ * DeferErrorIfUnsupportedSubqueryRepartition checks that we can perform distributed planning for
  * the given subquery. If not, a deferred error is returned. The function recursively
  * does this check to all lower levels of the subquery.
  */

src/backend/distributed/planner/query_pushdown_planning.c

@@ -850,6 +850,18 @@ DeferredErrorIfUnsupportedRecurringTuplesJoin(
 }
 
 
+/*
+ * CanPushdownSubquery checks if we can push down the given
+ * subquery to worker nodes.
+ */
+bool
+CanPushdownSubquery(Query *subqueryTree, bool outerMostQueryHasLimit)
+{
+	return DeferErrorIfCannotPushdownSubquery(subqueryTree, outerMostQueryHasLimit) ==
+		   NULL;
+}
+
+
 /*
  * DeferErrorIfCannotPushdownSubquery checks if we can push down the given
  * subquery to worker nodes. If we cannot push down the subquery, this function

src/backend/distributed/planner/recursive_planning.c

@@ -889,7 +889,7 @@ ShouldRecursivelyPlanSubquery(Query *subquery, RecursivePlanningContext *context
 		 * do not contain any other local tables.
 		 */
 	}
-	else if (DeferErrorIfCannotPushdownSubquery(subquery, false) == NULL)
+	else if (CanPushdownSubquery(subquery, false))
 	{
 		/*
 		 * We should do one more check for the distribution key equality.

src/include/distributed/query_pushdown_planning.h

@@ -22,7 +22,7 @@
 /* Config variables managed via guc.c */
 extern bool SubqueryPushdown;
 
-
+extern bool CanPushdownSubquery(Query *subqueryTree, bool outerMostQueryHasLimit);
 extern bool ShouldUseSubqueryPushDown(Query *originalQuery, Query *rewrittenQuery,
 									  PlannerRestrictionContext *plannerRestrictionContext);
 extern bool JoinTreeContainsSubquery(Query *query);