Fix access permission checks for distributed relations

With this commit, we add the range table list of the original query to our
custom plan. Therefore, PostgreSQL can check relations in the original query
for access permissions and error out if the proper access is not granted.

src/backend/distributed/planner/multi_planner.c

@@ -454,6 +454,9 @@ FinalizeNonRouterPlan(PlannedStmt *localPlan, MultiPlan *multiPlan,
 	finalPlan->queryId = localPlan->queryId;
 	finalPlan->utilityStmt = localPlan->utilityStmt;
 
+	/* add original range table list for access permission checks */
+	finalPlan->rtable = list_concat(finalPlan->rtable, localPlan->rtable);
+
 	return finalPlan;
 }
 
@@ -473,7 +476,7 @@ FinalizeRouterPlan(PlannedStmt *localPlan, CustomScan *customScan)
 	List *targetList = NIL;
 	List *columnNameList = NIL;
 
-	/* we will have only one range table entry */
+	/* we will have custom scan range table entry as the first one in the list */
 	int customScanRangeTableIndex = 1;
 
 	/* build a targetlist to read from the custom scan output */
@@ -514,6 +517,9 @@ FinalizeRouterPlan(PlannedStmt *localPlan, CustomScan *customScan)
 	remoteScanRangeTableEntry = RemoteScanRangeTableEntry(columnNameList);
 	routerPlan->rtable = list_make1(remoteScanRangeTableEntry);
 
+	/* add original range table list for access permission checks */
+	routerPlan->rtable = list_concat(routerPlan->rtable, localPlan->rtable);
+
 	routerPlan->canSetTag = true;
 	routerPlan->relationOids = NIL;