sql: populate information_schema.triggers

rafiss · rafiss · commit 4ed111a8a03b · 2025-05-23T17:17:30.000-04:00
Previously, the information_schema.triggers table was unimplemented and always returned zero rows. This made it impossible to query trigger metadata through standard SQL information schema views. This change implements the populate function for information_schema.triggers, allowing users to query trigger information. The implementation: Note that transition tables (action_reference_old_table/new_table) will only be populated once statement-level triggers are supported. Currently, these columns return NULL for row-level triggers. Fixes #143534 Release note (sql change): The information_schema.triggers table is now populated with trigger metadata. Users can query this table to see all triggers defined in their database, including the trigger name, timing (BEFORE/AFTER), event type (INSERT/UPDATE/DELETE), and associated function. Each trigger event appears as a separate row in the table.
diff --git a/pkg/ccl/logictestccl/testdata/logic_test/triggers b/pkg/ccl/logictestccl/testdata/logic_test/triggers
@@ -4499,3 +4499,192 @@ statement ok
 DROP FUNCTION f1;
 
 subtest end
+
+# ==============================================================================
+# Test information_schema.triggers
+# ==============================================================================
+
+subtest information_schema_triggers
+
+# Create test tables and trigger functions
+statement ok
+CREATE TABLE test_triggers (
+    id INT PRIMARY KEY,
+    name TEXT,
+    value INT
+);
+
+statement ok
+CREATE TABLE audit_log (
+    id SERIAL PRIMARY KEY,
+    table_name TEXT,
+    operation TEXT,
+    timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);
+
+statement ok
+CREATE FUNCTION trigger_func1() RETURNS TRIGGER AS $$
+  BEGIN
+    INSERT INTO audit_log (table_name, operation)
+    VALUES (TG_TABLE_NAME, TG_OP);
+    RETURN NEW;
+  END;
+$$ LANGUAGE PLpgSQL;
+
+statement ok
+CREATE FUNCTION trigger_func2() RETURNS TRIGGER AS $$
+  BEGIN
+    RAISE NOTICE 'Trigger fired';
+    RETURN NEW;
+  END;
+$$ LANGUAGE PLpgSQL;
+
+statement ok
+CREATE TRIGGER after_insert_row
+AFTER INSERT ON test_triggers
+FOR EACH ROW
+EXECUTE FUNCTION trigger_func1();
+
+statement ok
+CREATE TRIGGER before_update_row
+BEFORE UPDATE ON test_triggers
+FOR EACH ROW
+WHEN ((NEW).value > 100)
+EXECUTE FUNCTION trigger_func2();
+
+statement ok
+CREATE TRIGGER after_delete_row
+AFTER DELETE ON test_triggers
+FOR EACH ROW
+EXECUTE FUNCTION trigger_func1();
+
+query TTTTTTITTTTT colnames
+SELECT 
+    trigger_catalog,
+    trigger_schema,
+    trigger_name,
+    event_manipulation,
+    event_object_schema,
+    event_object_table,
+    action_order,
+    action_orientation,
+    action_timing,
+    action_reference_old_table,
+    action_reference_new_table,
+    created
+FROM information_schema.triggers
+WHERE event_object_table = 'test_triggers'
+ORDER BY trigger_name;
+----
+trigger_catalog  trigger_schema  trigger_name       event_manipulation  event_object_schema  event_object_table  action_order  action_orientation  action_timing  action_reference_old_table  action_reference_new_table  created
+test             public          after_delete_row   DELETE              public               test_triggers       NULL          ROW                 AFTER          NULL                        NULL                        NULL
+test             public          after_insert_row   INSERT              public               test_triggers       NULL          ROW                 AFTER          NULL                        NULL                        NULL
+test             public          before_update_row  UPDATE              public               test_triggers       NULL          ROW                 BEFORE         NULL                        NULL                        NULL
+
+# Test trigger with WHEN condition.
+query TTT colnames
+SELECT 
+    trigger_name,
+    action_condition,
+    action_statement
+FROM information_schema.triggers
+WHERE trigger_name = 'before_update_row';
+----
+trigger_name       action_condition     action_statement
+before_update_row  ((new).value > 100)  EXECUTE FUNCTION trigger_func2()
+
+# Create trigger with transition tables.
+statement ok
+CREATE FUNCTION trigger_func3() RETURNS TRIGGER AS $$
+  BEGIN
+    RETURN NULL;
+  END;
+$$ LANGUAGE PLpgSQL;
+
+# TODO(sql-queries): Enable tests for statement-level triggers when supported.
+# statement ok
+# CREATE TRIGGER after_update_transition
+# AFTER UPDATE ON test_triggers
+# REFERENCING OLD TABLE AS old_data NEW TABLE AS new_data
+# FOR EACH STATEMENT
+# EXECUTE FUNCTION trigger_func3();
+
+# TODO(sql-queries): Enable tests for statement-level triggers when supported.
+# query TTTTT colnames
+# SELECT 
+#     trigger_name,
+#     action_orientation,
+#     action_reference_old_table,
+#     action_reference_new_table,
+#     action_reference_old_row
+# FROM information_schema.triggers
+# WHERE trigger_name = 'after_update_transition';
+# ----
+# trigger_name             action_orientation  action_reference_old_table  action_reference_new_table  action_reference_old_row
+# after_update_transition  STATEMENT           old_data                    new_data                    NULL
+
+# Test multiple event types (create a trigger for multiple events).
+statement ok
+CREATE TRIGGER multi_event_trigger
+BEFORE INSERT OR UPDATE OR DELETE ON test_triggers
+FOR EACH ROW
+EXECUTE FUNCTION trigger_func1();
+
+# Each event should appear as a separate row.
+query TTT colnames
+SELECT 
+    trigger_name,
+    event_manipulation,
+    action_timing
+FROM information_schema.triggers
+WHERE trigger_name = 'multi_event_trigger'
+ORDER BY event_manipulation;
+----
+trigger_name         event_manipulation  action_timing
+multi_event_trigger  DELETE              BEFORE
+multi_event_trigger  INSERT              BEFORE
+multi_event_trigger  UPDATE              BEFORE
+
+# Create a schema and add a trigger there.
+statement ok
+CREATE SCHEMA other_schema;
+
+statement ok
+CREATE TABLE other_schema.test_table (id INT PRIMARY KEY, data TEXT);
+
+statement ok
+CREATE TRIGGER other_schema_trigger
+AFTER INSERT ON other_schema.test_table
+FOR EACH ROW
+EXECUTE FUNCTION trigger_func1();
+
+query TI colnames
+SELECT 
+    trigger_schema,
+    count(*) AS trigger_count
+FROM information_schema.triggers
+WHERE trigger_catalog = 'test'
+GROUP BY trigger_schema
+ORDER BY trigger_schema;
+----
+trigger_schema  trigger_count
+other_schema    1
+public          7
+
+# Clean up
+statement ok
+DROP TABLE test_triggers CASCADE;
+
+statement ok
+DROP TABLE other_schema.test_table CASCADE;
+
+statement ok
+DROP SCHEMA other_schema;
+
+statement ok
+DROP TABLE audit_log CASCADE;
+
+statement ok
+DROP FUNCTION trigger_func1, trigger_func2, trigger_func3;
+
+subtest end
diff --git a/pkg/sql/information_schema.go b/pkg/sql/information_schema.go
@@ -2403,12 +2403,105 @@ var informationSchemaTriggeredUpdateColumnsTable = virtualSchemaTable{
 }
 
 var informationSchemaTriggersTable = virtualSchemaTable{
-	comment: "triggers was created for compatibility and is currently unimplemented",
-	schema:  vtable.InformationSchemaTriggers,
-	populate: func(ctx context.Context, p *planner, _ catalog.DatabaseDescriptor, addRow func(...tree.Datum) error) error {
-		return nil
+	comment: `triggers contains information about triggers
+https://www.postgresql.org/docs/current/infoschema-triggers.html`,
+	schema: vtable.InformationSchemaTriggers,
+	populate: func(ctx context.Context, p *planner, dbContext catalog.DatabaseDescriptor, addRow func(...tree.Datum) error) error {
+		opts := forEachTableDescOptions{virtualOpts: hideVirtual} /* virtual schemas have no triggers */
+		return forEachTableDesc(ctx, p, dbContext, opts,
+			func(ctx context.Context, descCtx tableDescContext) error {
+				db, sc, table := descCtx.database, descCtx.schema, descCtx.table
+				dbNameStr := tree.NewDString(db.GetName())
+				scNameStr := tree.NewDString(sc.GetName())
+				tbNameStr := tree.NewDString(table.GetName())
+
+				triggers := table.GetTriggers()
+				for i := range triggers {
+					trigger := &triggers[i]
+
+					// Process each event for the trigger.
+					for _, event := range trigger.Events {
+						var eventManipulation string
+						switch event.Type {
+						case semenumpb.TriggerEventType_INSERT:
+							eventManipulation = "INSERT"
+						case semenumpb.TriggerEventType_UPDATE:
+							eventManipulation = "UPDATE"
+						case semenumpb.TriggerEventType_DELETE:
+							eventManipulation = "DELETE"
+						case semenumpb.TriggerEventType_TRUNCATE:
+							eventManipulation = "TRUNCATE"
+						}
+
+						var actionTiming string
+						switch trigger.ActionTime {
+						case semenumpb.TriggerActionTime_BEFORE:
+							actionTiming = "BEFORE"
+						case semenumpb.TriggerActionTime_AFTER:
+							actionTiming = "AFTER"
+						case semenumpb.TriggerActionTime_INSTEAD_OF:
+							actionTiming = "INSTEAD OF"
+						}
+
+						actionOrientation := "STATEMENT"
+						if trigger.ForEachRow {
+							actionOrientation = "ROW"
+						}
+
+						// Build the action statement.
+						funcDesc, err := p.Descriptors().ByIDWithLeased(p.Txn()).Get().Function(ctx, trigger.FuncID)
+						if err != nil {
+							return err
+						}
+						funcName := tree.Name(funcDesc.GetName())
+						actionStatement := fmt.Sprintf(`EXECUTE FUNCTION %s`, funcName.String())
+						if len(trigger.FuncArgs) > 0 {
+							actionStatement += fmt.Sprintf("(%s)", strings.Join(trigger.FuncArgs, ", "))
+						} else {
+							actionStatement += "()"
+						}
+
+						// Handle action condition (WHEN clause).
+						var actionCondition tree.Datum = tree.DNull
+						if trigger.WhenExpr != "" {
+							actionCondition = tree.NewDString(trigger.WhenExpr)
+						}
+
+						// Handle transition table names
+						var oldTableName, newTableName tree.Datum = tree.DNull, tree.DNull
+						if trigger.OldTransitionAlias != "" {
+							oldTableName = tree.NewDString(trigger.OldTransitionAlias)
+						}
+						if trigger.NewTransitionAlias != "" {
+							newTableName = tree.NewDString(trigger.NewTransitionAlias)
+						}
+
+						if err := addRow(
+							dbNameStr,                          // trigger_catalog
+							scNameStr,                          // trigger_schema
+							tree.NewDString(trigger.Name),      // trigger_name
+							tree.NewDString(eventManipulation), // event_manipulation
+							dbNameStr,                          // event_object_catalog
+							scNameStr,                          // event_object_schema
+							tbNameStr,                          // event_object_table
+							tree.DNull,                         // action_order
+							actionCondition,                    // action_condition
+							tree.NewDString(actionStatement),   // action_statement
+							tree.NewDString(actionOrientation), // action_orientation
+							tree.NewDString(actionTiming),      // action_timing
+							oldTableName,                       // action_reference_old_table
+							newTableName,                       // action_reference_new_table
+							tree.DNull,                         // action_reference_old_row
+							tree.DNull,                         // action_reference_new_row
+							tree.DNull,                         // created
+						); err != nil {
+							return err
+						}
+					}
+				}
+				return nil
+			})
 	},
-	unimplemented: true,
 }
 
 var informationSchemaTablesExtensionsTable = virtualSchemaTable{
