Fix memory context bug executing TRUNCATE

Inside the `process_truncate` function is created a new relations list
removing the distributed hypertables and this new list is assigned to
the current statement relation list. This new list is allocated into
the `PortalContext` that is destroyed at the end of the statement
execution.

The problem arise on the subsequent `TRUNCATE` call because the
compiled plpgsql code is cached into another memory context and the
elements of the relations inside this cache is pointing to an invalid
memory area because the `PortalContext` is destroyed.

Fixed it by allocating the new relations list to the `TopMemoryContext`
but just when the new list is different than the original.

Fixes #3580, #3622, #3181

src/process_utility.c

@@ -908,11 +908,13 @@ handle_truncate_hypertable(ProcessUtilityArgs *args, TruncateStmt *stmt, Hyperta
 static DDLResult
 process_truncate(ProcessUtilityArgs *args)
 {
+	MemoryContext oldctx = MemoryContextSwitchTo(TopMemoryContext);
 	TruncateStmt *stmt = (TruncateStmt *) args->parsetree;
 	Cache *hcache = ts_hypertable_cache_pin();
 	ListCell *cell;
 	List *hypertables = NIL;
 	List *relations = NIL;
+	bool list_changed = false;
 
 	/* For all hypertables, we drop the now empty chunks. We also propagate the
 	 * TRUNCATE call to the compressed version of the hypertable, if it exists.
@@ -931,7 +933,12 @@ process_truncate(ProcessUtilityArgs *args)
 		relid = RangeVarGetRelid(rv, AccessExclusiveLock, true);
 
 		if (!OidIsValid(relid))
+		{
+			/* We should add invalid relations to the list to raise error on the
+			 * standard_ProcessUtility when we're trying to TRUNCATE a nonexistent relation */
+			relations = lappend(relations, rv);
 			continue;
+		}
 
 		switch (get_rel_relkind(relid))
 		{
@@ -955,6 +962,9 @@ process_truncate(ProcessUtilityArgs *args)
 					/* Invalidate the entire continuous aggregate since it no
 					 * longer has any data */
 					ts_cm_functions->continuous_agg_invalidate(ht, PG_INT64_MIN, PG_INT64_MAX);
+
+					/* mark list as changed because we'll add the materialization hypertable */
+					list_changed = true;
 				}
 
 				relations = lappend(relations, rv);
@@ -999,6 +1009,9 @@ process_truncate(ProcessUtilityArgs *args)
 
 					if (!hypertable_is_distributed(ht))
 						relations = lappend(relations, rv);
+					else
+						/* mark list as changed because we'll not add the distributed hypertable */
+						list_changed = true;
 				}
 				break;
 			}
@@ -1008,10 +1021,14 @@ process_truncate(ProcessUtilityArgs *args)
 		}
 	}
 
-	/* Update relations list to include only tables that hold data. On an
-	 * access node, distributed hypertables hold no data and chunks are
-	 * foreign tables, so those tables are excluded. */
-	stmt->relations = relations;
+	/* Update relations list just when changed to include only tables
+	 * that hold data. On an access node, distributed hypertables hold
+	 * no data and chunks are foreign tables, so those tables are excluded. */
+	if (list_changed)
+		stmt->relations = relations;
+	else
+		/* Free the list if it was not changed */
+		pfree(relations);
 
 	if (stmt->relations != NIL)
 	{
@@ -1048,6 +1065,8 @@ process_truncate(ProcessUtilityArgs *args)
 
 	ts_cache_release(hcache);
 
+	MemoryContextSwitchTo(oldctx);
+
 	return DDL_DONE;
 }
 

test/expected/truncate.out

@@ -152,6 +152,58 @@ SELECT * FROM truncate_normal;
      1
 (1 row)
 
+-- fix for bug #3580
+\set ON_ERROR_STOP 0
+TRUNCATE nonexistentrelation;
+ERROR:  relation "nonexistentrelation" does not exist
+\set ON_ERROR_STOP 1
+CREATE TABLE truncate_nested (color int);
+INSERT INTO truncate_nested VALUES (2);
+SELECT * FROM truncate_normal, truncate_nested;
+ color | color 
+-------+-------
+     1 |     2
+(1 row)
+
+CREATE FUNCTION fn_truncate_nested()
+RETURNS trigger LANGUAGE plpgsql
+AS $$
+BEGIN
+    TRUNCATE truncate_nested;
+    RETURN NEW;
+END;
+$$;
+CREATE TRIGGER tg_truncate_nested
+    BEFORE TRUNCATE ON truncate_normal
+    FOR EACH STATEMENT EXECUTE FUNCTION fn_truncate_nested();
+TRUNCATE truncate_normal;
+SELECT * FROM truncate_normal, truncate_nested;
+ color | color 
+-------+-------
+(0 rows)
+
+INSERT INTO truncate_normal VALUES (3);
+INSERT INTO truncate_nested VALUES (4);
+SELECT * FROM truncate_normal, truncate_nested;
+ color | color 
+-------+-------
+     3 |     4
+(1 row)
+
+TRUNCATE truncate_normal;
+SELECT * FROM truncate_normal, truncate_nested;
+ color | color 
+-------+-------
+(0 rows)
+
+INSERT INTO truncate_normal VALUES (5);
+INSERT INTO truncate_nested VALUES (6);
+SELECT * FROM truncate_normal, truncate_nested;
+ color | color 
+-------+-------
+     5 |     6
+(1 row)
+
 SELECT * FROM test.show_subtables('"two_Partitions"');
                  Child                  | Tablespace 
 ----------------------------------------+------------
@@ -174,8 +226,8 @@ SELECT * FROM "two_Partitions";
 ------------+-----------+----------+----------+----------+-------------
 (0 rows)
 
-SELECT * FROM truncate_normal;
- color 
--------
+SELECT * FROM truncate_normal, truncate_nested;
+ color | color 
+-------+-------
 (0 rows)
 

test/sql/truncate.sql

@@ -66,10 +66,47 @@ CREATE TABLE truncate_normal (color int);
 INSERT INTO truncate_normal VALUES (1);
 SELECT * FROM truncate_normal;
 
+-- fix for bug #3580
+\set ON_ERROR_STOP 0
+TRUNCATE nonexistentrelation;
+\set ON_ERROR_STOP 1
+CREATE TABLE truncate_nested (color int);
+INSERT INTO truncate_nested VALUES (2);
+
+SELECT * FROM truncate_normal, truncate_nested;
+
+CREATE FUNCTION fn_truncate_nested()
+RETURNS trigger LANGUAGE plpgsql
+AS $$
+BEGIN
+    TRUNCATE truncate_nested;
+    RETURN NEW;
+END;
+$$;
+
+CREATE TRIGGER tg_truncate_nested
+    BEFORE TRUNCATE ON truncate_normal
+    FOR EACH STATEMENT EXECUTE FUNCTION fn_truncate_nested();
+
+TRUNCATE truncate_normal;
+SELECT * FROM truncate_normal, truncate_nested;
+
+INSERT INTO truncate_normal VALUES (3);
+INSERT INTO truncate_nested VALUES (4);
+
+SELECT * FROM truncate_normal, truncate_nested;
+
+TRUNCATE truncate_normal;
+SELECT * FROM truncate_normal, truncate_nested;
+
+INSERT INTO truncate_normal VALUES (5);
+INSERT INTO truncate_nested VALUES (6);
+SELECT * FROM truncate_normal, truncate_nested;
+
 SELECT * FROM test.show_subtables('"two_Partitions"');
 
 TRUNCATE "two_Partitions", truncate_normal CASCADE;
 -- should be empty
 SELECT * FROM test.show_subtables('"two_Partitions"');
 SELECT * FROM "two_Partitions";
-SELECT * FROM truncate_normal;
+SELECT * FROM truncate_normal, truncate_nested;

tsl/test/expected/chunk_api.out

@@ -552,7 +552,6 @@ _timescaledb_internal._dist_hyper_2_5_chunk|        4|f         |          0|
 -- Clean up
 RESET ROLE;
 TRUNCATE disttable;
-TRUNCATE costtable;
 SELECT * FROM delete_data_node('data_node_1', force => true);
 WARNING:  insufficient number of data nodes for distributed hypertable "disttable"
 NOTICE:  the number of partitions in dimension "device" was decreased to 1

tsl/test/sql/chunk_api.sql

@@ -254,7 +254,6 @@ $$);
 -- Clean up
 RESET ROLE;
 TRUNCATE disttable;
-TRUNCATE costtable;
 SELECT * FROM delete_data_node('data_node_1', force => true);
 SELECT * FROM delete_data_node('data_node_2', force => true);
 DROP DATABASE :DN_DBNAME_1;