stop distributing views with no distributed dependency if GUC DistributeLocalViews is set false. (#6083)

src/backend/distributed/commands/view.c

@@ -35,11 +35,50 @@
 #include "utils/lsyscache.h"
 #include "utils/syscache.h"
 
+/*
+ * GUC controls some restrictions for local objects. For example,
+ * if it is disabled, a local view with no distributed relation dependency
+ * will be created even if it has circular dependency and will not
+ * log error or warning. Citus will normally restrict that behaviour for the
+ * local views. e.g CREATE TABLE local_t (a int);
+ *                  CREATE VIEW vv1 as SELECT * FROM local_t;
+ *					CREATE OR REPLACE VIEW vv2 as SELECT * FROM vv1;
+ *
+ * When the GUC is disabled, citus also wont distribute the local
+ * view which has no citus relation dependency to workers. Otherwise, it distributes
+ * them by default. e.g create view v as select 1;
+ */
+bool EnforceLocalObjectRestrictions = true;
+
 static List * FilterNameListForDistributedViews(List *viewNamesList, bool missing_ok);
 static void AppendQualifiedViewNameToCreateViewCommand(StringInfo buf, Oid viewOid);
 static void AppendViewDefinitionToCreateViewCommand(StringInfo buf, Oid viewOid);
 static void AppendAliasesToCreateViewCommand(StringInfo createViewCommand, Oid viewOid);
 static void AppendOptionsToCreateViewCommand(StringInfo createViewCommand, Oid viewOid);
+static bool ViewHasDistributedRelationDependency(ObjectAddress *viewObjectAddress);
+
+/*
+ * ViewHasDistributedRelationDependency returns true if given view at address has
+ * any distributed relation dependency.
+ */
+static bool
+ViewHasDistributedRelationDependency(ObjectAddress *viewObjectAddress)
+{
+	List *dependencies = GetAllDependenciesForObject(viewObjectAddress);
+	ObjectAddress *dependency = NULL;
+
+	foreach_ptr(dependency, dependencies)
+	{
+		if (dependency->classId == RelationRelationId && IsAnyObjectDistributed(
+				list_make1(dependency)))
+		{
+			return true;
+		}
+	}
+
+	return false;
+}
+
 
 /*
  * PreprocessViewStmt is called during the planning phase for CREATE OR REPLACE VIEW
@@ -110,6 +149,36 @@ PostprocessViewStmt(Node *node, const char *queryString)
 		return NIL;
 	}
 
+	/*
+	 * If it is disabled, a local view with no distributed relation dependency
+	 * will be created even if it has circular dependency and will not
+	 * log error or warning. Citus will normally restrict that behaviour for the
+	 * local views. e.g CREATE TABLE local_t (a int);
+	 *                  CREATE VIEW vv1 as SELECT * FROM local_t;
+	 *					CREATE OR REPLACE VIEW vv2 as SELECT * FROM vv1;
+	 *
+	 * When the GUC is disabled, citus also wont distribute the local
+	 * view which has no citus relation dependency to workers. Otherwise, it distributes
+	 * them by default. e.g create view v as select 1;
+	 *
+	 * We disable local object restrictions during pg vanilla tests to not diverge
+	 * from Postgres in terms of error messages.
+	 */
+	if (!EnforceLocalObjectRestrictions)
+	{
+		/* we asserted that we have only one address. */
+		ObjectAddress *viewAddress = linitial(viewAddresses);
+
+		if (!ViewHasDistributedRelationDependency(viewAddress))
+		{
+			/*
+			 * The local view has no distributed relation dependency, so we can allow
+			 * it to be created even if it has circular dependency.
+			 */
+			return NIL;
+		}
+	}
+
 	EnsureAllObjectDependenciesExistOnAllNodes(viewAddresses);
 
 	/* We have already asserted that we have exactly 1 address in the addresses. */

src/backend/distributed/metadata/dependency.c

@@ -843,7 +843,10 @@ ErrorOrWarnIfObjectHasUnsupportedDependency(const ObjectAddress *objectAddress)
 		}
 		else
 		{
-			RaiseDeferredError(errMsg, WARNING);
+			if (EnableUnsupportedFeatureMessages)
+			{
+				RaiseDeferredError(errMsg, WARNING);
+			}
 		}
 
 		return true;

src/backend/distributed/shared_library_init.c

@@ -1204,6 +1204,17 @@ RegisterCitusConfigVariables(void)
 		GUC_NO_SHOW_ALL,
 		NULL, NULL, NULL);
 
+	DefineCustomBoolVariable(
+		"citus.enforce_object_restrictions_for_local_objects",
+		gettext_noop(
+			"Controls some restrictions for local objects."),
+		NULL,
+		&EnforceLocalObjectRestrictions,
+		true,
+		PGC_USERSET,
+		GUC_NO_SHOW_ALL,
+		NULL, NULL, NULL);
+
 	DefineCustomIntVariable(
 		"citus.executor_slow_start_interval",
 		gettext_noop("Time to wait between opening connections to the same worker node"),

src/include/distributed/commands.h

@@ -31,6 +31,8 @@ extern bool EnableUnsafeTriggers;
 
 extern int MaxMatViewSizeToAutoRecreate;
 
+extern bool EnforceLocalObjectRestrictions;
+
 extern void SwitchToSequentialAndLocalExecutionIfRelationNameTooLong(Oid relationId,
 																	 char *
 																	 finalRelationName);

src/test/regress/expected/view_propagation.out

@@ -855,6 +855,85 @@ HINT:  Use DROP MATERIALIZED VIEW to remove a materialized view.
 DROP MATERIALIZED VIEW IF EXISTS axx.temp_view_to_drop;
 DROP MATERIALIZED VIEW IF EXISTS axx.temp_view_to_drop;
 NOTICE:  materialized view "temp_view_to_drop" does not exist, skipping
+-- Test the GUC citus.enforce_object_restrictions_for_local_objects
+SET search_path to view_prop_schema;
+CREATE TABLE local_t (a int);
+-- tests when citus.enforce_object_restrictions_for_local_objects=true
+SET citus.enforce_object_restrictions_for_local_objects TO true;
+-- views will be created locally with warnings
+CREATE VIEW vv1 as SELECT * FROM local_t;
+WARNING:  "view vv1" has dependency to "table local_t" that is not in Citus' metadata
+DETAIL:  "view vv1" will be created only locally
+HINT:  Distribute "table local_t" first to distribute "view vv1"
+CREATE OR REPLACE VIEW vv2 as SELECT * FROM vv1;
+WARNING:  "view vv2" has dependency to "table local_t" that is not in Citus' metadata
+DETAIL:  "view vv2" will be created only locally
+HINT:  Distribute "table local_t" first to distribute "view vv2"
+-- view will fail due to local circular dependency
+CREATE OR REPLACE VIEW vv1 as SELECT * FROM vv2;
+ERROR:  Citus can not handle circular dependencies between distributed objects
+DETAIL:  "view vv1" circularly depends itself, resolve circular dependency first
+-- local view with no citus relation dependency will be distributed
+CREATE VIEW v_dist AS SELECT 1;
+-- show that the view is in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid = 'v_dist'::regclass;
+ count
+---------------------------------------------------------------------
+    1
+(1 row)
+
+-- tests when citus.enforce_object_restrictions_for_local_objects=false
+SET citus.enforce_object_restrictions_for_local_objects TO false;
+SET citus.enable_unsupported_feature_messages TO false;
+-- views will be created locally without errors OR warnings
+CREATE VIEW vv3 as SELECT * FROM local_t;
+CREATE OR REPLACE VIEW vv4 as SELECT * FROM vv3;
+CREATE OR REPLACE VIEW vv3 as SELECT * FROM vv4;
+-- show that views are NOT in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid IN ('vv3'::regclass, 'vv4'::regclass);
+ count
+---------------------------------------------------------------------
+    0
+(1 row)
+
+-- local view with no citus relation dependency will NOT be distributed
+CREATE VIEW v_local_only AS SELECT 1;
+-- show that the view is NOT in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid = 'v_local_only'::regclass;
+ count
+---------------------------------------------------------------------
+    0
+(1 row)
+
+-- distribute the local table and check the distribution of dependent views
+SELECT create_distributed_table('local_t', 'a');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- show that views with no circular dependency are in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid IN ('vv1'::regclass, 'vv2'::regclass);
+ count
+---------------------------------------------------------------------
+    2
+(1 row)
+
+-- show that views with circular dependency are NOT in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid IN ('vv3'::regclass, 'vv4'::regclass);
+ count
+---------------------------------------------------------------------
+    0
+(1 row)
+
+-- show that we cannot re-create the circular views ever
+CREATE OR REPLACE VIEW vv3 as SELECT * FROM local_t;
+CREATE OR REPLACE VIEW vv4 as SELECT * FROM vv3;
+CREATE OR REPLACE VIEW vv3 as SELECT * FROM vv4;
+ERROR:  Citus can not handle circular dependencies between distributed objects
+DETAIL:  "view vv3" circularly depends itself, resolve circular dependency first
+RESET citus.enable_unsupported_feature_messages;
+RESET citus.enforce_object_restrictions_for_local_objects;
 SET client_min_messages TO ERROR;
 DROP SCHEMA view_prop_schema_inner CASCADE;
 DROP SCHEMA view_prop_schema, axx CASCADE;

src/test/regress/pg_regress_multi.pl

@@ -503,6 +503,9 @@ if(!$vanillaDev && $vanillatest)
 
     # we disable citus related unwanted messages to not break postgres vanilla test behaviour.
     push(@pgOptions, "citus.enable_unsupported_feature_messages=false");
+
+    # we disable some restrictions for local objects like local views to not break postgres vanilla test behaviour.
+    push(@pgOptions, "citus.enforce_object_restrictions_for_local_objects=false");
 }
 
 if ($useMitmproxy)

src/test/regress/sql/view_propagation.sql

@@ -497,6 +497,50 @@ DROP VIEW IF EXISTS axx.temp_view_to_drop;
 DROP MATERIALIZED VIEW IF EXISTS axx.temp_view_to_drop;
 DROP MATERIALIZED VIEW IF EXISTS axx.temp_view_to_drop;
 
+-- Test the GUC citus.enforce_object_restrictions_for_local_objects
+SET search_path to view_prop_schema;
+CREATE TABLE local_t (a int);
+
+-- tests when citus.enforce_object_restrictions_for_local_objects=true
+SET citus.enforce_object_restrictions_for_local_objects TO true;
+-- views will be created locally with warnings
+CREATE VIEW vv1 as SELECT * FROM local_t;
+CREATE OR REPLACE VIEW vv2 as SELECT * FROM vv1;
+-- view will fail due to local circular dependency
+CREATE OR REPLACE VIEW vv1 as SELECT * FROM vv2;
+-- local view with no citus relation dependency will be distributed
+CREATE VIEW v_dist AS SELECT 1;
+-- show that the view is in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid = 'v_dist'::regclass;
+
+-- tests when citus.enforce_object_restrictions_for_local_objects=false
+SET citus.enforce_object_restrictions_for_local_objects TO false;
+SET citus.enable_unsupported_feature_messages TO false;
+-- views will be created locally without errors OR warnings
+CREATE VIEW vv3 as SELECT * FROM local_t;
+CREATE OR REPLACE VIEW vv4 as SELECT * FROM vv3;
+CREATE OR REPLACE VIEW vv3 as SELECT * FROM vv4;
+-- show that views are NOT in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid IN ('vv3'::regclass, 'vv4'::regclass);
+-- local view with no citus relation dependency will NOT be distributed
+CREATE VIEW v_local_only AS SELECT 1;
+-- show that the view is NOT in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid = 'v_local_only'::regclass;
+
+-- distribute the local table and check the distribution of dependent views
+SELECT create_distributed_table('local_t', 'a');
+-- show that views with no circular dependency are in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid IN ('vv1'::regclass, 'vv2'::regclass);
+-- show that views with circular dependency are NOT in pg_dist_object
+SELECT COUNT(*) FROM pg_dist_object WHERE objid IN ('vv3'::regclass, 'vv4'::regclass);
+
+-- show that we cannot re-create the circular views ever
+CREATE OR REPLACE VIEW vv3 as SELECT * FROM local_t;
+CREATE OR REPLACE VIEW vv4 as SELECT * FROM vv3;
+CREATE OR REPLACE VIEW vv3 as SELECT * FROM vv4;
+
+RESET citus.enable_unsupported_feature_messages;
+RESET citus.enforce_object_restrictions_for_local_objects;
 SET client_min_messages TO ERROR;
 DROP SCHEMA view_prop_schema_inner CASCADE;
 DROP SCHEMA view_prop_schema, axx CASCADE;