citus/src/test/regress/expected/cursors.out

CREATE SCHEMA cursors;
SET search_path TO cursors;
CREATE TABLE distributed_table (key int, value text);
SELECT create_distributed_table('distributed_table', 'key');
 create_distributed_table
---------------------------------------------------------------------

(1 row)

-- load some data, but not very small amounts because RETURN QUERY in plpgsql
-- hard codes the cursor fetch to 50 rows on PG 12, though they might increase
-- it sometime in the future, so be mindful
INSERT INTO distributed_table SELECT i  % 10, i::text FROM  generate_series(0, 1000) i;
CREATE OR REPLACE FUNCTION simple_cursor_on_dist_table(cursor_name refcursor) RETURNS refcursor AS '
BEGIN
    OPEN $1 FOR SELECT DISTINCT key FROM distributed_table ORDER BY 1;
    RETURN $1;
END;
' LANGUAGE plpgsql;
CREATE OR REPLACE FUNCTION cursor_with_intermediate_result_on_dist_table(cursor_name refcursor) RETURNS refcursor AS '
BEGIN
    OPEN $1 FOR
		WITH cte_1 AS (SELECT * FROM distributed_table OFFSET 0)
			SELECT DISTINCT key FROM distributed_table WHERE value in (SELECT value FROM cte_1) ORDER BY 1;
    RETURN $1;
END;
' LANGUAGE plpgsql;
CREATE OR REPLACE FUNCTION cursor_with_intermediate_result_on_dist_table_with_param(cursor_name refcursor, filter text) RETURNS refcursor AS '
BEGIN
    OPEN $1 FOR
		WITH cte_1 AS (SELECT * FROM distributed_table WHERE value < $2 OFFSET 0)
			SELECT DISTINCT key FROM distributed_table WHERE value in (SELECT value FROM cte_1) ORDER BY 1;
    RETURN $1;
END;
' LANGUAGE plpgsql;
-- pretty basic query with cursors
-- Citus should plan/execute once and pull
-- the results to coordinator, then serve it
-- from the coordinator
BEGIN;
	SELECT simple_cursor_on_dist_table('cursor_1');
 simple_cursor_on_dist_table
---------------------------------------------------------------------
 cursor_1
(1 row)

	SET LOCAL citus.log_intermediate_results TO ON;
	SET LOCAL client_min_messages TO DEBUG1;
	FETCH 5 IN cursor_1;
 key
---------------------------------------------------------------------
   0
   1
   2
   3
   4
(5 rows)

	FETCH 50 IN cursor_1;
 key
---------------------------------------------------------------------
   5
   6
   7
   8
   9
(5 rows)

	FETCH ALL IN cursor_1;
 key
---------------------------------------------------------------------
(0 rows)

COMMIT;
BEGIN;
	SELECT cursor_with_intermediate_result_on_dist_table('cursor_1');
 cursor_with_intermediate_result_on_dist_table
---------------------------------------------------------------------
 cursor_1
(1 row)

	-- multiple FETCH commands should not trigger re-running the subplans
	SET LOCAL citus.log_intermediate_results TO ON;
	SET LOCAL client_min_messages TO DEBUG1;
	FETCH 5 IN cursor_1;
DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
 key
---------------------------------------------------------------------
   0
   1
   2
   3
   4
(5 rows)

	FETCH 1 IN cursor_1;
 key
---------------------------------------------------------------------
   5
(1 row)

	FETCH ALL IN cursor_1;
 key
---------------------------------------------------------------------
   6
   7
   8
   9
(4 rows)

	FETCH 5 IN cursor_1;
 key
---------------------------------------------------------------------
(0 rows)

COMMIT;
BEGIN;
	SELECT cursor_with_intermediate_result_on_dist_table_with_param('cursor_1', '600');
 cursor_with_intermediate_result_on_dist_table_with_param
---------------------------------------------------------------------
 cursor_1
(1 row)

	-- multiple FETCH commands should not trigger re-running the subplans
	-- also test with parameters
	SET LOCAL citus.log_intermediate_results TO ON;
	SET LOCAL client_min_messages TO DEBUG1;
	FETCH 1 IN cursor_1;
DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
 key
---------------------------------------------------------------------
   0
(1 row)

	FETCH 1 IN cursor_1;
 key
---------------------------------------------------------------------
   1
(1 row)

	FETCH 1 IN cursor_1;
 key
---------------------------------------------------------------------
   2
(1 row)

	FETCH 1 IN cursor_1;
 key
---------------------------------------------------------------------
   3
(1 row)

	FETCH 1 IN cursor_1;
 key
---------------------------------------------------------------------
   4
(1 row)

	FETCH 1 IN cursor_1;
 key
---------------------------------------------------------------------
   5
(1 row)

	FETCH ALL IN cursor_1;
 key
---------------------------------------------------------------------
   6
   7
   8
   9
(4 rows)

COMMIT;
 CREATE OR REPLACE FUNCTION value_counter() RETURNS TABLE(counter text) LANGUAGE PLPGSQL AS $function$
 BEGIN
         return query
WITH cte AS
  (SELECT dt.value
   FROM distributed_table dt
   WHERE dt.value in
       (SELECT value
        FROM distributed_table p
        GROUP BY p.value
        HAVING count(*) > 0))

 SELECT * FROM cte;
END;
$function$ ;
SET citus.log_intermediate_results TO ON;
SET client_min_messages TO DEBUG1;
\set VERBOSITY terse
SELECT count(*) from (SELECT value_counter())  as foo;
DEBUG:  CTE cte is going to be inlined via distributed planning
DEBUG:  generating subplan XXX_1 for subquery SELECT value FROM cursors.distributed_table p GROUP BY value HAVING (count(*) OPERATOR(pg_catalog.>) 0)
DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT value FROM (SELECT dt.value FROM cursors.distributed_table dt WHERE (dt.value OPERATOR(pg_catalog.=) ANY (SELECT intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(value text)))) cte
DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
 count
---------------------------------------------------------------------
  1001
(1 row)

BEGIN;
	SELECT count(*) from (SELECT value_counter())  as foo;
DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
 count
---------------------------------------------------------------------
  1001
(1 row)

COMMIT;
-- suppress NOTICEs
SET client_min_messages TO ERROR;
DROP SCHEMA cursors CASCADE;