Check groupid existence hackily while removing metadata

src/backend/distributed/executor/adaptive_executor.c

@@ -2187,7 +2187,7 @@ LookupTaskPlacementHostAndPort(ShardPlacement *taskPlacement, char **nodeName,
 		 * there were changes in pg_dist_node and we will get those invalidations
 		 * in LookupNodeForGroup.
 		 */
-		WorkerNode *workerNode = LookupNodeForGroup(taskPlacement->groupId);
+		WorkerNode *workerNode = LookupNodeForGroup(taskPlacement->groupId, false);
 		*nodeName = workerNode->workerName;
 		*nodePort = workerNode->workerPort;
 	}

src/backend/distributed/metadata/metadata_cache.c

@@ -833,7 +833,12 @@ ResolveGroupShardPlacement(GroupShardPlacement *groupShardPlacement,
 
 	ShardPlacement *shardPlacement = CitusMakeNode(ShardPlacement);
 	int32 groupId = groupShardPlacement->groupId;
-	WorkerNode *workerNode = LookupNodeForGroup(groupId);
+	WorkerNode *workerNode = LookupNodeForGroup(groupId, true);
+
+	if (workerNode == NULL)
+	{
+		return NULL;
+	}
 
 	/* copy everything into shardPlacement but preserve the header */
 	CitusNode header = shardPlacement->type;
@@ -929,7 +934,7 @@ LookupNodeByNodeIdOrError(uint32 nodeId)
  * appropriate error message.
  */
 WorkerNode *
-LookupNodeForGroup(int32 groupId)
+LookupNodeForGroup(int32 groupId, bool checkExistence)
 {
 	bool foundAnyNodes = false;
 
@@ -953,10 +958,20 @@ LookupNodeForGroup(int32 groupId)
 	}
 
 	if (!foundAnyNodes)
+	{
+		if (checkExistence)
+		{
+			ereport(NOTICE, (errmsg("there is a shard placement in node group %d but "
+						"there are no nodes in that group", groupId)));
+
+			return NULL;
+		}
+		else
 		{
 			ereport(ERROR, (errmsg("there is a shard placement in node group %d but "
 						"there are no nodes in that group", groupId)));
 		}
+	}
 
 	switch (ReadFromSecondaries)
 	{
@@ -1014,6 +1029,11 @@ ShardPlacementListIncludingOrphanedPlacements(uint64 shardId)
 																	tableEntry,
 																	shardIndex);
 
+		if (shardPlacement == NULL)
+		{
+			return NULL;
+		}
+
 		placementList = lappend(placementList, shardPlacement);
 	}
 

src/backend/distributed/operations/shard_rebalancer.c

@@ -391,7 +391,7 @@ FullShardPlacementList(Oid relationId, ArrayType *excludedShardArray)
 			 placementIndex++)
 		{
 			GroupShardPlacement *groupPlacement = &placementArray[placementIndex];
-			WorkerNode *worker = LookupNodeForGroup(groupPlacement->groupId);
+			WorkerNode *worker = LookupNodeForGroup(groupPlacement->groupId, false);
 			ShardPlacement *placement = CitusMakeNode(ShardPlacement);
 			placement->shardId = groupPlacement->shardId;
 			placement->shardLength = groupPlacement->shardLength;

src/backend/distributed/operations/worker_node_manager.c

@@ -455,7 +455,7 @@ CoordinatorNodeIfAddedAsWorkerOrError()
 {
 	ErrorIfCoordinatorNotAddedAsWorkerNode();
 
-	WorkerNode *coordinatorNode = LookupNodeForGroup(COORDINATOR_GROUP_ID);
+	WorkerNode *coordinatorNode = LookupNodeForGroup(COORDINATOR_GROUP_ID, false);
 
 	WorkerNode *coordinatorNodeCopy = palloc0(sizeof(WorkerNode));
 	*coordinatorNodeCopy = *coordinatorNode;

src/backend/distributed/worker/worker_drop_protocol.c

@@ -268,6 +268,12 @@ worker_drop_distributed_table_metadata_only(PG_FUNCTION_ARGS)
 		uint64 shardId = *shardIdPointer;
 
 		List *shardPlacementList = ShardPlacementListIncludingOrphanedPlacements(shardId);
+		if (shardPlacementList == NULL)
+		{
+			ereport(NOTICE, (errmsg("placement for relation with oid %d does not exist, skipping", relationId)));
+			PG_RETURN_VOID();
+		}
+
 		ShardPlacement *placement = NULL;
 		foreach_ptr(placement, shardPlacementList)
 		{

src/include/distributed/metadata_cache.h

@@ -211,7 +211,7 @@ extern bool HasAnyNodes(void);
 extern HTAB * GetWorkerNodeHash(void);
 extern WorkerNode * LookupNodeByNodeId(uint32 nodeId);
 extern WorkerNode * LookupNodeByNodeIdOrError(uint32 nodeId);
-extern WorkerNode * LookupNodeForGroup(int32 groupId);
+extern WorkerNode * LookupNodeForGroup(int32 groupId, bool checkExistence);
 
 /* namespace oids */
 extern Oid CitusCatalogNamespaceId(void);

src/include/distributed/metadata_sync.h

@@ -75,7 +75,7 @@ extern Oid GetAttributeTypeOid(Oid relationId, AttrNumber attnum);
 #define REMOVE_ALL_CLUSTERED_TABLES_ONLY_COMMAND \
 	"SELECT worker_drop_distributed_table_only(logicalrelid::regclass::text) FROM pg_dist_partition"
 #define REMOVE_ALL_CLUSTERED_TABLES_METADATA_ONLY_COMMAND \
-	"SELECT worker_drop_distributed_table_metadata_only(logicalrelid) FROM pg_dist_partition"
+	"SELECT worker_drop_distributed_table_metadata_only(logicalrelid::oid) FROM pg_dist_partition"
 #define REMOVE_ALL_CLUSTERED_TABLES_COMMAND \
 	"SELECT worker_drop_distributed_table(logicalrelid::regclass::text) FROM pg_dist_partition"
 #define DISABLE_DDL_PROPAGATION "SET citus.enable_ddl_propagation TO 'off'"