Change the order in which the locks are acquired.

src/backend/distributed/utils/resource_lock.c

@@ -707,13 +707,10 @@ SerializeNonCommutativeWrites(List *shardIntervalList, LOCKMODE lockMode)
 	}
 
 	List *replicatedShardList = NIL;
-	if (AnyTableReplicated(shardIntervalList, &replicatedShardList))
+	bool anyTableReplicated = AnyTableReplicated(shardIntervalList, &replicatedShardList);
-	{
-		if (ClusterHasKnownMetadataWorkers() && !IsFirstWorkerNode())
-		{
-			LockShardListResourcesOnFirstWorker(lockMode, replicatedShardList);
-		}
 
+	if (anyTableReplicated)
+	{
 		ShardInterval *firstShardInterval =
 			(ShardInterval *) linitial(replicatedShardList);
 		if (ReferenceTableShardId(firstShardInterval->shardId))
@@ -728,7 +725,10 @@ SerializeNonCommutativeWrites(List *shardIntervalList, LOCKMODE lockMode)
 			LockReferencedReferenceShardResources(firstShardInterval->shardId, lockMode);
 		}
 	}
-
+	if (anyTableReplicated && ClusterHasKnownMetadataWorkers() && !IsFirstWorkerNode())
+	{
+		LockShardListResourcesOnFirstWorker(lockMode, replicatedShardList);
+	}
 	LockShardListResources(shardIntervalList, lockMode);
 }
 

src/test/regress/expected/issue_7477.out

@@ -45,16 +45,16 @@ SELECT * FROM master_run_on_worker(
     true);
  node_name | node_port | success |                                      result
 ---------------------------------------------------------------------
- localhost |     57638 | f       | ERROR:  deadlock detected
+ localhost |     57638 | t       | UPDATE 1
+ localhost |     57637 | t       | UPDATE 1
+ localhost |     57637 | t       | UPDATE 1
+ localhost |     57638 | t       | UPDATE 1
+ localhost |     57637 | t       | UPDATE 1
+ localhost |     57638 | t       | UPDATE 1
+ localhost |     57637 | t       | UPDATE 1
+ localhost |     57638 | t       | UPDATE 1
+ localhost |     57638 | t       | UPDATE 1
  localhost |     57637 | t       | UPDATE 1
- localhost |     57637 | f       | ERROR:  deadlock detected
- localhost |     57638 | f       | ERROR:  deadlock detected
- localhost |     57637 | f       | ERROR:  canceling the transaction since it was involved in a distributed deadlock
- localhost |     57638 | f       | ERROR:  deadlock detected
- localhost |     57637 | f       | ERROR:  deadlock detected
- localhost |     57638 | f       | ERROR:  deadlock detected
- localhost |     57638 | f       | ERROR:  canceling the transaction since it was involved in a distributed deadlock
- localhost |     57637 | f       | ERROR:  deadlock detected
 (10 rows)
 
 --- cleanup

src/test/regress/sql/issue_7477.sql

@@ -1,5 +1,5 @@
 
---- Test for updating a table that has a foreign key reference to another reference table. 
+--- Test for updating a table that has a foreign key reference to another reference table.
 --- Issue #7477: Distributed deadlock after issuing a simple UPDATE statement
 --- https://github.com/citusdata/citus/issues/7477
 
@@ -15,7 +15,7 @@ CREATE TABLE table2 (
 SELECT create_reference_table('table2');
 INSERT INTO table2 VALUES (1, 'test');
 
---- Runs the update command in parallel on workers. 
+--- Runs the update command in parallel on workers.
 --- Due to bug #7477, before the fix, the result is non-deterministic
 --- and have several rows of the form:
 ---  localhost |     57638 | f       | ERROR:  deadlock detected
@@ -23,7 +23,7 @@ INSERT INTO table2 VALUES (1, 'test');
 ---  localhost |     57637 | f       | ERROR:  canceling the transaction since it was involved in a distributed deadlock
 
 SELECT * FROM master_run_on_worker(
-    ARRAY['localhost', 'localhost','localhost', 'localhost','localhost', 
+    ARRAY['localhost', 'localhost','localhost', 'localhost','localhost',
             'localhost','localhost', 'localhost','localhost', 'localhost']::text[],
     ARRAY[57638, 57637, 57637, 57638, 57637, 57638, 57637, 57638, 57638, 57637]::int[],
     ARRAY['UPDATE table2 SET info = ''test_update'' WHERE id = 1',