Properly cache fast-path remote non-SELECT queries

Basically, apply what we do for SELECT

src/backend/distributed/executor/citus_custom_scan.c

@@ -325,7 +325,6 @@ CitusBeginReadOnlyScan(CustomScanState *node, EState *estate, int eflags)
 		/* job query no longer has parameters, so we should not send any */
 		workerJob->parametersInJobQueryResolved = true;
 
-
 		/* do the heavy lifting of deparsing unless we cannot find any cache */
 		SetTaskQueryString(task, DeparseTaskQuery(task, workerJob->jobQuery));
 	}
@@ -372,7 +371,6 @@ CitusBeginModifyScan(CustomScanState *node, EState *estate, int eflags)
 	{
 		ExecuteCoordinatorEvaluableExpressions(jobQuery, planState);
 
-		/* job query no longer has parameters, so we should not send any */
 		workerJob->parametersInJobQueryResolved = true;
 	}
 
@@ -439,30 +437,38 @@ CitusBeginModifyScan(CustomScanState *node, EState *estate, int eflags)
 		workerJob->taskList = FirstReplicaAssignTaskList(workerJob->taskList);
 	}
 
-
-	/*
-	 * Now that we have populated the task placements we can determine whether
-	 * any of them are local to this node and cache a plan if needed.
-	 */
 	if (IsFastPathPlanCachingSupported(workerJob, originalDistributedPlan))
 	{
 		Task *task = linitial(workerJob->taskList);
 
-		/*
-		 * We are going to execute this task locally. If it's not already in
-		 * the cache, create a local plan now and add it to the cache. During
-		 * execution, we will get the plan from the cache.
-		 *
-		 * WARNING: In this function we'll use the original plan with the original
-		 * query tree, meaning parameters and function calls are back and we'll
-		 * redo evaluation in the local (Postgres) executor. The reason we do this
-		 * is that we only need to cache one generic plan per shard.
-		 *
-		 * The plan will be cached across executions when originalDistributedPlan
-		 * represents a prepared statement.
-		 */
-		CacheFastPathPlanForShardQuery(task, workerJob, originalDistributedPlan,
-									   estate->es_param_list_info);
+		FastPathPlanCache *fastPathPlanCache =
+			CacheFastPathPlanForShardQuery(task, workerJob, originalDistributedPlan,
+										   estate->es_param_list_info);
+		if (fastPathPlanCache == NULL)
+		{
+			/* job query no longer has parameters, so we should not send any */
+
+			/* do the heavy lifting of deparsing unless we cannot find any cache */
+
+			ListCell *taskCell = NULL;
+
+			foreach(taskCell, workerJob->taskList)
+			{
+				Task *taskI = (Task *) lfirst(taskCell);
+
+				SetTaskQueryString(taskI, DeparseTaskQuery(taskI, workerJob->jobQuery));
+			}
+		}
+		else if (fastPathPlanCache->queryString != NULL)
+		{
+			task->parametersInQueryStringResolved = false;
+
+			SetTaskQueryString(task, fastPathPlanCache->queryString);
+
+			/* TODO: we have this due to MarkUnreferencedExternParams. Can we find another way? */
+			workerJob->jobQuery = copyObject(
+				originalDistributedPlan->workerJob->jobQuery);
+		}
 	}
 
 	MemoryContextSwitchTo(oldContext);

src/backend/distributed/planner/fast_path_plan_cache.c

@@ -345,6 +345,15 @@ IsFastPathPlanCachingSupported(Job *currentJob, DistributedPlan *originalDistrib
 		return false;
 	}
 
+	if (currentJob->requiresCoordinatorEvaluation)
+	{
+		/*
+		 * We want functions to be evaluated on the coordinator, and
+		 * we do not want to put into the cache.
+		 */
+		return false;
+	}
+
 	if (!currentJob->deferredPruning)
 	{
 		/*

src/backend/distributed/planner/multi_router_planner.c

@@ -1707,6 +1707,7 @@ RouterInsertTaskList(Query *query, bool parametersInQueryResolved,
 		modifyTask->taskPlacementList = ActiveShardPlacementList(
 			modifyRoute->shardId);
 		modifyTask->parametersInQueryStringResolved = parametersInQueryResolved;
+		modifyTask->deferredPruning = true;
 
 		insertTaskList = lappend(insertTaskList, modifyTask);
 	}
@@ -1810,6 +1811,7 @@ RouterJob(Query *originalQuery, PlannerRestrictionContext *plannerRestrictionCon
 	{
 		Job *job = CreateJob(originalQuery);
 		job->deferredPruning = true;
+		job->requiresCoordinatorEvaluation = requiresCoordinatorEvaluation;
 
 		ereport(DEBUG2, (errmsg("Deferred pruning for a fast-path router "
 								"query")));