Fix to delete the pg_ivm_immv entry when an IMMV is dropped

Makefile

@@ -11,7 +11,7 @@ PGFILEDESC = "pg_ivm - incremental view maintenance on PostgreSQL"
 EXTENSION = pg_ivm
 DATA = pg_ivm--1.0.sql
 
-REGRESS = pg_ivm
+REGRESS = pg_ivm create_immv
 
 PG_CONFIG = pg_config
 PGXS := $(shell $(PG_CONFIG) --pgxs)

expected/create_immv.out

@@ -0,0 +1,43 @@
+CREATE TABLE t (i int PRIMARY KEY);
+INSERT INTO t SELECT generate_series(1, 100);
+SELECT create_immv('mv', 'SELECT * FROM t');
+NOTICE:  created index "mv_index" on immv "mv"
+ create_immv 
+-------------
+         100
+(1 row)
+
+SELECT create_immv(' mv2 ( x  ) ', 'SELECT * FROM t WHERE i%2 = 0');
+NOTICE:  created index "mv2_index" on immv "mv2"
+ create_immv 
+-------------
+          50
+(1 row)
+
+SELECT create_immv('mv3', 'WITH d AS (DELETE FROM t RETURNING NULL) SELECT * FROM t');
+ERROR:  materialized views must not use data-modifying statements in WITH
+SELECT immvrelid FROM pg_ivm_immv ORDER BY 1;
+ immvrelid 
+-----------
+ mv
+ mv2
+(2 rows)
+
+DROP TABLE t;
+ERROR:  cannot drop table t because other objects depend on it
+DETAIL:  table mv depends on table t
+table mv2 depends on table t
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP TABLE mv;
+SELECT immvrelid FROM pg_ivm_immv ORDER BY 1;
+ immvrelid 
+-----------
+ mv2
+(1 row)
+
+DROP TABLE mv2;
+SELECT immvrelid FROM pg_ivm_immv ORDER BY 1;
+ immvrelid 
+-----------
+(0 rows)
+

pg_ivm--1.0.sql

@@ -39,3 +39,28 @@ CREATE FUNCTION "IVM_prevent_immv_change"()
 RETURNS trigger 
 AS 'MODULE_PATHNAME', 'IVM_prevent_immv_change'
 LANGUAGE C;
+
+
+/*
+ * DDL trigger that removes entry from pg_ivm_immv
+ */
+CREATE FUNCTION pg_ivm_sql_drop_trigger_func()
+RETURNS event_trigger AS $$
+DECLARE
+	pg_class_oid	OID;
+	relids			REGCLASS[];
+
+BEGIN
+	pg_class_oid = 'pg_catalog.pg_class'::regclass;
+
+	/* Find relids to remove */
+	DELETE FROM pg_catalog.pg_ivm_immv
+	USING pg_catalog.pg_event_trigger_dropped_objects() AS events
+	WHERE immvrelid = events.objid AND
+	      events.classid = pg_class_oid AND events.objsubid = 0;
+END
+$$ LANGUAGE plpgsql;
+
+CREATE EVENT TRIGGER pg_ivm_sql_drop_trigger
+ON sql_drop
+EXECUTE PROCEDURE pg_catalog.pg_ivm_sql_drop_trigger_func();

sql/create_immv.sql

@@ -0,0 +1,17 @@
+CREATE TABLE t (i int PRIMARY KEY);
+INSERT INTO t SELECT generate_series(1, 100);
+
+SELECT create_immv('mv', 'SELECT * FROM t');
+SELECT create_immv(' mv2 ( x  ) ', 'SELECT * FROM t WHERE i%2 = 0');
+
+SELECT create_immv('mv3', 'WITH d AS (DELETE FROM t RETURNING NULL) SELECT * FROM t');
+
+SELECT immvrelid FROM pg_ivm_immv ORDER BY 1;
+
+DROP TABLE t;
+
+DROP TABLE mv;
+SELECT immvrelid FROM pg_ivm_immv ORDER BY 1;
+
+DROP TABLE mv2;
+SELECT immvrelid FROM pg_ivm_immv ORDER BY 1;