Fix crash when removing an inactive node

src/backend/distributed/utils/reference_table_utils.c

@@ -406,25 +406,29 @@ DeleteAllReferenceTablePlacementsFromNode(char *workerName, uint32 workerPort)
 	referenceTableList = SortList(referenceTableList, CompareOids);
 	foreach(referenceTableCell, referenceTableList)
 	{
+		GroupShardPlacement *placement = NULL;
+		StringInfo deletePlacementCommand = makeStringInfo();
+
 		uint32 workerGroup = GroupForNode(workerName, workerPort);
 
 		Oid referenceTableId = lfirst_oid(referenceTableCell);
 		List *placements = GroupShardPlacementsForTableOnGroup(referenceTableId,
 															   workerGroup);
-		GroupShardPlacement *placement = (GroupShardPlacement *) linitial(placements);
+		if (list_length(placements) == 0)
+		{
+			/* this happens if the node was previously disabled */
+			continue;
+		}
 
-		uint64 shardId = placement->shardId;
+		placement = (GroupShardPlacement *) linitial(placements);
-		uint64 placementId = placement->placementId;
 
-		StringInfo deletePlacementCommand = makeStringInfo();
+		LockShardDistributionMetadata(placement->shardId, ExclusiveLock);
 
-		LockShardDistributionMetadata(shardId, ExclusiveLock);
+		DeleteShardPlacementRow(placement->placementId);
-
-		DeleteShardPlacementRow(placementId);
 
 		appendStringInfo(deletePlacementCommand,
 						 "DELETE FROM pg_dist_placement WHERE placementid=%lu",
-						 placementId);
+						 placement->placementId);
 		SendCommandToWorkers(WORKERS_WITH_METADATA, deletePlacementCommand->data);
 	}
 }

src/test/regress/expected/multi_remove_node_reference_table.out

@@ -169,6 +169,27 @@ NOTICE:  Replicating reference table "remove_node_reference_table" to the node l
  (1380001,1380001,localhost,57638,default,f,t)
 (1 row)
 
+-- try to disable the node before removing it (this used to crash)
+SELECT master_disable_node('localhost', :worker_2_port);
+ master_disable_node 
+---------------------
+ 
+(1 row)
+
+SELECT master_remove_node('localhost', :worker_2_port);
+ master_remove_node 
+--------------------
+ 
+(1 row)
+
+-- re-add the node for the next test
+SELECT master_add_node('localhost', :worker_2_port);
+NOTICE:  Replicating reference table "remove_node_reference_table" to the node localhost:57638
+                master_add_node                
+-----------------------------------------------
+ (1380002,1380002,localhost,57638,default,f,t)
+(1 row)
+
 -- remove node in a transaction and ROLLBACK
 -- status before master_remove_node
 SELECT COUNT(*) FROM pg_dist_node WHERE nodeport = :worker_2_port;
@@ -389,7 +410,7 @@ SELECT master_add_node('localhost', :worker_2_port);
 NOTICE:  Replicating reference table "remove_node_reference_table" to the node localhost:57638
                 master_add_node                
 -----------------------------------------------
- (1380002,1380002,localhost,57638,default,f,t)
+ (1380003,1380003,localhost,57638,default,f,t)
 (1 row)
 
 -- test inserting a value then removing a node in a transaction
@@ -518,7 +539,7 @@ SELECT master_add_node('localhost', :worker_2_port);
 NOTICE:  Replicating reference table "remove_node_reference_table" to the node localhost:57638
                 master_add_node                
 -----------------------------------------------
- (1380003,1380003,localhost,57638,default,f,t)
+ (1380004,1380004,localhost,57638,default,f,t)
 (1 row)
 
 -- test executing DDL command then removing a node in a transaction
@@ -643,7 +664,7 @@ SELECT master_add_node('localhost', :worker_2_port);
 NOTICE:  Replicating reference table "remove_node_reference_table" to the node localhost:57638
                 master_add_node                
 -----------------------------------------------
- (1380004,1380004,localhost,57638,default,f,t)
+ (1380005,1380005,localhost,57638,default,f,t)
 (1 row)
 
 -- test DROP table after removing a node in a transaction
@@ -711,7 +732,7 @@ SELECT * FROM pg_dist_colocation WHERE colocationid = 1380000;
 SELECT master_add_node('localhost', :worker_2_port);
                 master_add_node                
 -----------------------------------------------
- (1380005,1380005,localhost,57638,default,f,t)
+ (1380006,1380006,localhost,57638,default,f,t)
 (1 row)
 
 -- re-create remove_node_reference_table
@@ -846,7 +867,7 @@ NOTICE:  Replicating reference table "remove_node_reference_table" to the node l
 NOTICE:  Replicating reference table "table1" to the node localhost:57638
                 master_add_node                
 -----------------------------------------------
- (1380006,1380006,localhost,57638,default,f,t)
+ (1380007,1380007,localhost,57638,default,f,t)
 (1 row)
 
 -- test with master_disable_node
@@ -963,7 +984,7 @@ NOTICE:  Replicating reference table "remove_node_reference_table" to the node l
 NOTICE:  Replicating reference table "table1" to the node localhost:57638
              master_activate_node              
 -----------------------------------------------
- (1380006,1380006,localhost,57638,default,f,t)
+ (1380007,1380007,localhost,57638,default,f,t)
 (1 row)
 
 -- DROP tables to clean workspace

src/test/regress/sql/multi_remove_node_reference_table.sql

@@ -105,6 +105,13 @@ SELECT master_remove_node('localhost', :worker_2_port);
 -- re-add the node for next tests
 SELECT master_add_node('localhost', :worker_2_port);
 
+-- try to disable the node before removing it (this used to crash)
+SELECT master_disable_node('localhost', :worker_2_port);
+SELECT master_remove_node('localhost', :worker_2_port);
+
+-- re-add the node for the next test
+SELECT master_add_node('localhost', :worker_2_port);
+
 -- remove node in a transaction and ROLLBACK
 
 -- status before master_remove_node