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 doesn't changing the original relation list of the
statement and instead of call the `standard_ProcessUtility` we call
direct the `ExecuteTruncate` over the new created list without the
distributed hypertables.

Fixes timescale#3580, timescale#3622, timescale#3181

src/process_utility.c

@@ -914,6 +914,8 @@ process_truncate(ProcessUtilityArgs *args)
 	List *hypertables = NIL;
 	List *relations = NIL;
 
+	Assert(IsA(stmt, TruncateStmt));
+
 	/* 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.
 	 */
@@ -1008,15 +1010,12 @@ 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;
-
-	if (stmt->relations != NIL)
+	/* Truncate only regular tables */
+	if (relations != NIL)
 	{
-		/* Call standard PostgreSQL handler for remaining tables */
-		prev_ProcessUtility(args);
+		TruncateStmt relations_stmt = *stmt;
+		relations_stmt.relations = relations;
+		ExecuteTruncate(&relations_stmt);
 	}
 
 	/* For all hypertables, we drop the now empty chunks */

test/expected/truncate.out

@@ -152,6 +152,54 @@ SELECT * FROM truncate_normal;
      1
 (1 row)
 
+-- fix for bug #3580
+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 truncate_nested()
+RETURNS trigger LANGUAGE plpgsql
+AS $$
+BEGIN
+    TRUNCATE truncate_nested;
+    RETURN NEW;
+END;
+$$;
+CREATE TRIGGER truncate_nested
+    BEFORE TRUNCATE ON truncate_normal
+    FOR EACH STATEMENT EXECUTE FUNCTION 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 +222,8 @@ 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 +66,44 @@ CREATE TABLE truncate_normal (color int);
 INSERT INTO truncate_normal VALUES (1);
 SELECT * FROM truncate_normal;
 
+-- fix for bug #3580
+CREATE TABLE truncate_nested (color int);
+INSERT INTO truncate_nested VALUES (2);
+
+SELECT * FROM truncate_normal, truncate_nested;
+
+CREATE FUNCTION truncate_nested()
+RETURNS trigger LANGUAGE plpgsql
+AS $$
+BEGIN
+    TRUNCATE truncate_nested;
+    RETURN NEW;
+END;
+$$;
+
+CREATE TRIGGER truncate_nested
+    BEFORE TRUNCATE ON truncate_normal
+    FOR EACH STATEMENT EXECUTE FUNCTION 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/src/remote/dist_ddl.c

@@ -471,19 +471,20 @@ dist_ddl_preprocess(ProcessUtilityArgs *args)
 		case T_TruncateStmt:
 		{
 			TruncateStmt *stmt = (TruncateStmt *) args->parsetree;
-			/* Calculate number of regular tables. Note that distributed
-			 * hypertables are filtered from the relations list in
-			 * process_utility.c, so the list might actually be empty. */
+
+			/* Calculate number of regular tables. Note that number of
+			 * distributed hypertables should be the same of the relations
+			 * list */
 			unsigned int num_regular_tables =
 				list_length(stmt->relations) - num_hypertables - num_dist_hypertable_members;
 
-			Assert(num_regular_tables <= list_length(stmt->relations));
+			Assert(num_regular_tables == list_length(stmt->relations));
 
 			/* We only support TRUNCATE on single distributed hypertables
 			 * since other tables might not exist on data nodes and multiple
 			 * distributed hypertables might be distributed across different
 			 * sets of nodes. */
-			if (num_dist_hypertables == 1 && num_regular_tables == 0 && num_hypertables == 0 &&
+			if (num_dist_hypertables == 1 && num_regular_tables == 1 && num_hypertables == 0 &&
 				num_dist_hypertable_members == 0)
 				set_dist_exec_type(DIST_DDL_EXEC_ON_START);
 			else