done

src/backend/distributed/commands/create_distributed_table.c

@@ -436,11 +436,6 @@ CreateDistributedTableConcurrently(Oid relationId, char *distributionColumnName,
 
 	char replicationModel = DecideDistTableReplicationModel(distributionMethod,
 															colocateWithTableName);
-	if (replicationModel != REPLICATION_MODEL_STREAMING)
-	{
-		ereport(ERROR, (errmsg("cannot create a replicated distributed "
-							   "table concurrently")));
-	}
 
 	/*
 	 * we fail transaction before local table conversion if the table could not be colocated with
@@ -450,6 +445,19 @@ CreateDistributedTableConcurrently(Oid relationId, char *distributionColumnName,
 	if (!IsColocateWithDefault(colocateWithTableName) && !IsColocateWithNone(
 			colocateWithTableName))
 	{
+        if (replicationModel != REPLICATION_MODEL_STREAMING)
+        {
+            ereport(ERROR, (errmsg("cannot create distributed table "
+                                   "concurrently because Citus allows "
+                                   "concurrent table distribution only when "
+                                   "citus.shard_replication_factor = 1"),
+                            errhint("table %s is requested to be colocated "
+                                    "with %s which has "
+                                    "citus.shard_replication_factor > 1",
+                                    get_rel_name(relationId),
+                                    colocateWithTableName)));
+        }
+
 		EnsureColocateWithTableIsValid(relationId, distributionMethod,
 									   distributionColumnName,
 									   colocateWithTableName);

src/test/regress/expected/create_distributed_table_concurrently.out

@@ -47,7 +47,8 @@ select create_distributed_table('dist_1', 'a');
 set citus.shard_replication_factor to 1;
 create table dist_2(a int);
 select create_distributed_table_concurrently('dist_2', 'a', colocate_with=>'dist_1');
-ERROR:  cannot create a replicated distributed table concurrently
+ERROR:  cannot create distributed table concurrently because Citus allows concurrent table distribution only when citus.shard_replication_factor = 1
+HINT:  table dist_2 is requested to be colocated with dist_1 which has citus.shard_replication_factor > 1
 begin;
 select create_distributed_table_concurrently('test','key');
 ERROR:  create_distributed_table_concurrently cannot run inside a transaction block