Disallow adding local table with identity column to metadata (#4633)

pg_get_tableschemadef_string doesn't know how to deparse identity
columns so we cannot reflect those columns when creating shell
relation.
For this reason, we don't allow adding local tables -having identity cols-
to metadata.

src/backend/distributed/commands/citus_add_local_table_to_metadata.c

@@ -49,6 +49,7 @@ static void citus_add_local_table_to_metadata_internal(Oid relationId,
 													   bool cascadeViaForeignKeys);
 static void ErrorIfUnsupportedCreateCitusLocalTable(Relation relation);
 static void ErrorIfUnsupportedCitusLocalTableKind(Oid relationId);
+static void ErrorIfUnsupportedCitusLocalColumnDefinition(Relation relation);
 static List * GetShellTableDDLEventsForCitusLocalTable(Oid relationId);
 static uint64 ConvertLocalTableToShard(Oid relationId);
 static void RenameRelationToShardRelation(Oid shellRelationId, uint64 shardId);
@@ -338,6 +339,7 @@ ErrorIfUnsupportedCreateCitusLocalTable(Relation relation)
 	ErrorIfCoordinatorNotAddedAsWorkerNode();
 	ErrorIfUnsupportedCitusLocalTableKind(relationId);
 	EnsureTableNotDistributed(relationId);
+	ErrorIfUnsupportedCitusLocalColumnDefinition(relation);
 
 	/*
 	 * When creating other citus table types, we don't need to check that case as
@@ -405,6 +407,30 @@ ErrorIfUnsupportedCitusLocalTableKind(Oid relationId)
 }
 
 
+/*
+ * ErrorIfUnsupportedCitusLocalColumnDefinition errors out if given relation
+ * has unsupported column definition for citus local table creation.
+ */
+static void
+ErrorIfUnsupportedCitusLocalColumnDefinition(Relation relation)
+{
+	TupleDesc relationDesc = RelationGetDescr(relation);
+	if (RelationUsesIdentityColumns(relationDesc))
+	{
+		/*
+		 * pg_get_tableschemadef_string doesn't know how to deparse identity
+		 * columns so we cannot reflect those columns when creating shell
+		 * relation. For this reason, error out here.
+		 */
+		Oid relationId = relation->rd_id;
+		ereport(ERROR, (errmsg("cannot add %s to citus metadata since table "
+							   "has identity column",
+							   generate_qualified_relation_name(relationId)),
+						errhint("Drop the identity columns and re-try the command")));
+	}
+}
+
+
 /*
  * GetShellTableDDLEventsForCitusLocalTable returns a list of DDL commands
  * to create the shell table from scratch.

src/backend/distributed/commands/create_distributed_table.c

@@ -122,7 +122,6 @@ static void DropFKeysRelationInvolvedWithTableType(Oid relationId, int tableType
 static bool LocalTableEmpty(Oid tableId);
 static void CopyLocalDataIntoShards(Oid relationId);
 static List * TupleDescColumnNameList(TupleDesc tupleDescriptor);
-static bool RelationUsesIdentityColumns(TupleDesc relationDesc);
 static bool DistributionColumnUsesGeneratedStoredColumn(TupleDesc relationDesc,
 														Var *distributionColumn);
 static bool CanUseExclusiveConnections(Oid relationId, bool localTableEmpty);
@@ -1636,7 +1635,7 @@ TupleDescColumnNameList(TupleDesc tupleDescriptor)
  * RelationUsesIdentityColumns returns whether a given relation uses
  * GENERATED ... AS IDENTITY
  */
-static bool
+bool
 RelationUsesIdentityColumns(TupleDesc relationDesc)
 {
 	for (int attributeIndex = 0; attributeIndex < relationDesc->natts; attributeIndex++)

src/include/distributed/metadata_utility.h

@@ -249,6 +249,7 @@ extern void EnsureTableNotDistributed(Oid relationId);
 extern void EnsureReplicationSettings(Oid relationId, char replicationModel);
 extern void EnsureRelationExists(Oid relationId);
 extern bool RegularTable(Oid relationId);
+extern bool RelationUsesIdentityColumns(TupleDesc relationDesc);
 extern char * ConstructQualifiedShardName(ShardInterval *shardInterval);
 extern uint64 GetFirstShardId(Oid relationId);
 extern Datum StringToDatum(char *inputString, Oid dataType);

src/test/regress/expected/citus_local_tables.out

@@ -56,6 +56,18 @@ BEGIN;
   SELECT citus_add_local_table_to_metadata('temp_table');
 ERROR:  constraints on temporary tables may reference only temporary tables
 ROLLBACK;
+-- below two errors out since we don't support adding local tables
+-- having any identity columns to metadata
+BEGIN;
+  CREATE TABLE identity_cols_test (a int generated by default as identity (start with 42));
+  SELECT citus_add_local_table_to_metadata('identity_cols_test');
+ERROR:  cannot add citus_local_tables_test_schema.identity_cols_test to citus metadata since table has identity column
+ROLLBACK;
+BEGIN;
+  CREATE TABLE identity_cols_test (a int generated always as identity (increment by 42));
+  SELECT citus_add_local_table_to_metadata('identity_cols_test');
+ERROR:  cannot add citus_local_tables_test_schema.identity_cols_test to citus metadata since table has identity column
+ROLLBACK;
 -- creating citus local table having no data initially would work
 SELECT citus_add_local_table_to_metadata('citus_local_table_1');
  citus_add_local_table_to_metadata

src/test/regress/sql/citus_local_tables.sql

@@ -46,6 +46,18 @@ BEGIN;
   SELECT citus_add_local_table_to_metadata('temp_table');
 ROLLBACK;
 
+-- below two errors out since we don't support adding local tables
+-- having any identity columns to metadata
+BEGIN;
+  CREATE TABLE identity_cols_test (a int generated by default as identity (start with 42));
+  SELECT citus_add_local_table_to_metadata('identity_cols_test');
+ROLLBACK;
+
+BEGIN;
+  CREATE TABLE identity_cols_test (a int generated always as identity (increment by 42));
+  SELECT citus_add_local_table_to_metadata('identity_cols_test');
+ROLLBACK;
+
 -- creating citus local table having no data initially would work
 SELECT citus_add_local_table_to_metadata('citus_local_table_1');