Fix handling of non-regular relation RTEs in is_query_using_regular_relation (#4694)

When IMPLICIT_TRANSACTIONS is set to ON, queries with non-regular
relation RTEs (like for system views or CTEs) were not handled by
is_query_using_regular_relation_walker(), and the node was passed
to expression_tree_walker, which does not handle RTE nodes.

To fix this, we return false to let range_table_walker handle it.

Authored-by: Saurav Samantaray <sauravay@amazon.com>

Author: Vaurkhorov

contrib/babelfishpg_tsql/src/pl_exec.c

@@ -4606,6 +4606,7 @@ is_query_using_regular_relation_walker(Node *node, void *context)
         RangeTblEntry *rte = (RangeTblEntry *) node;
 		if (rte->rtekind == RTE_RELATION && rte->relkind == 'r')
 			return true;
+		return false;
     }
 
     if (IsA(node, Query))

test/JDBC/input/BABEL-IMPLICIT_TRAN.sql

@@ -238,6 +238,41 @@ DEALLOCATE implicit_tran_cursor;
 SELECT @@TRANCOUNT;
 GO
 
+-- Select from system view should start implicit transaction
+SELECT @@TRANCOUNT
+SELECT DISTINCT 'OK' FROM pg_stat_activity
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+
+-- Subquery in FROM should not error
+SELECT @@TRANCOUNT
+SELECT * FROM (SELECT 1 AS x) sub
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+
+-- Set-returning function in FROM should not error
+SELECT @@TRANCOUNT
+SELECT * FROM generate_series(1, 3)
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+
+-- CTE should not error
+SELECT @@TRANCOUNT
+WITH cte AS (SELECT 1 AS x) SELECT * FROM cte
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+
+-- VALUES clause in FROM should not error
+SELECT @@TRANCOUNT
+SELECT * FROM (VALUES (1), (2), (3)) AS t(x)
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+
 -- Cleanup
 SET IMPLICIT_TRANSACTIONS OFF
 GO

test/JDBC/sql_expected/BABEL-IMPLICIT_TRAN.out

@@ -590,6 +590,120 @@ int
 ~~END~~
 
 
+-- Select from system view should start implicit transaction
+SELECT @@TRANCOUNT
+SELECT DISTINCT 'OK' FROM pg_stat_activity
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+~~START~~
+int
+0
+~~END~~
+
+~~START~~
+text
+OK
+~~END~~
+
+~~START~~
+int
+1
+~~END~~
+
+
+-- Subquery in FROM should not error
+SELECT @@TRANCOUNT
+SELECT * FROM (SELECT 1 AS x) sub
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+~~START~~
+int
+0
+~~END~~
+
+~~START~~
+int
+1
+~~END~~
+
+~~START~~
+int
+0
+~~END~~
+
+
+-- Set-returning function in FROM should not error
+SELECT @@TRANCOUNT
+SELECT * FROM generate_series(1, 3)
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+~~START~~
+int
+0
+~~END~~
+
+~~START~~
+int
+1
+2
+3
+~~END~~
+
+~~START~~
+int
+0
+~~END~~
+
+
+-- CTE should not error
+SELECT @@TRANCOUNT
+WITH cte AS (SELECT 1 AS x) SELECT * FROM cte
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+~~START~~
+int
+0
+~~END~~
+
+~~START~~
+int
+1
+~~END~~
+
+~~START~~
+int
+0
+~~END~~
+
+
+-- VALUES clause in FROM should not error
+SELECT @@TRANCOUNT
+SELECT * FROM (VALUES (1), (2), (3)) AS t(x)
+SELECT @@TRANCOUNT
+IF @@TRANCOUNT > 0 COMMIT
+GO
+~~START~~
+int
+0
+~~END~~
+
+~~START~~
+int
+1
+2
+3
+~~END~~
+
+~~START~~
+int
+0
+~~END~~
+
+
 -- Cleanup
 SET IMPLICIT_TRANSACTIONS OFF
 GO