Generate query for the remote fast path query cache

Do not use yet, just generate

src/backend/distributed/planner/fast_path_plan_cache.c

@@ -28,6 +28,8 @@ static FastPathPlanCache * GetFastPathCachedPlan(Task *task,
 												 DistributedPlan *distributedPlan);
 static Query * GetLocalShardQueryForCache(Query *jobQuery, Task *task,
 										  ParamListInfo paramListInfo);
+static char * GetFastPathQueryStringForCache(Query *jobQuery, Task *task,
+											 ParamListInfo orig_paramListInfo);
 static char * DeparseLocalShardQuery(Query *jobQuery, List *relationShardList,
 									 Oid anchorDistributedTableId, int64 anchorShardId);
 static int ExtractParameterTypesForParamListInfo(ParamListInfo originalParamListInfo,
@@ -67,6 +69,8 @@ CacheFastPathPlanForShardQuery(Task *task, DistributedPlan *originalDistributedP
 	 * functions/params to have been evaluated in the cached plan.
 	 */
 	Query *jobQuery = copyObject(originalDistributedPlan->workerJob->jobQuery);
+	FastPathPlanCache *fastPathPlanCache = CitusMakeNode(FastPathPlanCache);
+
 	PlannedStmt *localPlan = NULL;
 
 	if (TaskAccessesLocalNode(task))
@@ -95,12 +99,16 @@ CacheFastPathPlanForShardQuery(Task *task, DistributedPlan *originalDistributedP
 		LockRelationOid(rangeTableEntry->relid, lockMode);
 
 		localPlan = planner(localShardQuery, NULL, 0, NULL);
+		fastPathPlanCache->localPlan = localPlan;
 	}
 	else
-	{ }
+	{
+		char *queryString =
+			GetFastPathQueryStringForCache(jobQuery, task, paramListInfo);
+
+		fastPathPlanCache->queryString = queryString;
+	}
 
-	FastPathPlanCache *fastPathPlanCache = CitusMakeNode(FastPathPlanCache);
-	fastPathPlanCache->localPlan = localPlan;
 	fastPathPlanCache->shardId = task->anchorShardId;
 	fastPathPlanCache->placementGroupIds = TaskGroupIdAccesses(task);
 
@@ -148,6 +156,28 @@ GetLocalShardQueryForCache(Query *jobQuery, Task *task, ParamListInfo orig_param
 }
 
 
+/*
+ * GetFastPathQueryStringForCache is a helper function which generates
+ * the local shard string based on the jobQuery. The function should
+ * not be used for generic purposes, it is specialized for local cached
+ * queries.
+ *
+ */
+static char *
+GetFastPathQueryStringForCache(Query *jobQuery, Task *task, ParamListInfo
+							   orig_paramListInfo)
+{
+	char *shardQueryString =
+		DeparseLocalShardQuery(jobQuery, task->relationShardList,
+							   task->anchorDistributedTableId,
+							   task->anchorShardId);
+	ereport(DEBUG5, (errmsg("Local shard query that is going to be cached: %s",
+							shardQueryString)));
+
+	return shardQueryString;
+}
+
+
 /*
  * DeparseLocalShardQuery is a helper function to deparse given jobQuery for the shard(s)
  * identified by the relationShardList, anchorDistributedTableId and anchorShardId.

src/backend/distributed/utils/citus_copyfuncs.c

@@ -340,6 +340,7 @@ CopyNodeFastPathPlanCache(COPYFUNC_ARGS)
 	COPY_SCALAR_FIELD(shardId);
 	COPY_NODE_FIELD(placementGroupIds);
 	COPY_NODE_FIELD(localPlan);
+	COPY_STRING_FIELD(queryString);
 }
 
 

src/include/distributed/multi_physical_planner.h

@@ -120,7 +120,24 @@ typedef struct FastPathPlanCache
 
 	uint64 shardId;
 	List *placementGroupIds;
+
+	/*
+	 * Cache can be found in different ways and therefore stored differently on the
+	 * definition.
+	 *
+	 * TODO: Ideally we only have either of the fields.
+	 * investigate UNION of a C struct and CopyNodeFastPathPlanCache.
+	 */
+
+	/* union */
+	/*{*/
+	/* if fast path cache is for a local shard */
 	PlannedStmt *localPlan;
+
+	/* if fast path cache is for a remote shard */
+	char *queryString;
+
+	/*} data;*/
 } FastPathPlanCache;