[GPU Logic Bug] SELECT <column> FROM <table> JOIN <table> WHERE <condition> Brings GPU Logic Bug

[qwebug]

Describe:

SELECT <column> FROM <table> JOIN <table> WHERE <condition> brings different results, when using CPU-only configurations and GPU-used configurations.

SQL with CPU-only Config:

CREATE TABLE t0(c0 smallint);
CREATE TABLE t2(LIKE t0);
INSERT INTO t0(c0) VALUES(1), (3), (4), (0);
INSERT INTO t2(c0) VALUES(2), (1), (0), (5), (1), (0);
CREATE SCHEMA extensions;
CREATE EXTENSION pg_strom WITH SCHEMA extensions;
SET pg_strom.enabled=off;
SELECT t0.c0 FROM t0 CROSS JOIN t2 WHERE ((((t0.c0)IS NOT DISTINCT FROM(t2.c0)))AND((t0.c0) BETWEEN SYMMETRIC (- (t2.c0)) AND (1)));

Result:

 c0 
----
  1
  0
  1
  0
(4 rows)

SQL with GPU-used Config:

BEGIN;
SET LOCAL pg_strom.enabled=on; 
SET LOCAL pg_strom.enable_gpuscan=on; 
SET LOCAL pg_strom.enable_gpuhashjoin=on; 
SET LOCAL pg_strom.enable_gpujoin=on;
SELECT t0.c0 FROM t0 CROSS JOIN t2 WHERE ((((t0.c0)IS NOT DISTINCT FROM(t2.c0)))AND((t0.c0) BETWEEN SYMMETRIC (- (t2.c0)) AND (1)));
COMMIT;

Result:

 c0 
----
  1
  1
  0
  0
(4 rows)

Environment:

Pg-strom Version: commit b1f04e4

PostgreSQL Version: 15.6 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-20), 64-bit

CUDA Version: 12.2

NVIDIA Driver Version: 535.171.04

[kaigai]

It is not a bug but by design.

SQL does not guarantee the order of results unless an explicit ORDER BY is not attached.

See the following results.
The result rows with c0=1 come from (0,1) (0,2) and (0,1) (0,5) pair, and the rows with c0=0 come from (0,4) (0,3) and (0,4) (0,6).

hoge=# set pg_strom.enabled = off;
SET
hoge=# SELECT t0.ctid, t2.ctid, t0.c0 FROM t0 CROSS JOIN t2 WHERE ((((t0.c0)IS NOT DISTINCT FROM(t2.c0)))AND((t0.c0) BETWEEN SYMMETRIC (- (t2.c0)) AND (1)));
 ctid  | ctid  | c0
-------+-------+----
 (0,1) | (0,2) |  1
 (0,4) | (0,3) |  0
 (0,1) | (0,5) |  1
 (0,4) | (0,6) |  0
(4 rows)

hoge=# set pg_strom.enabled = on;
SET
hoge=# SELECT t0.ctid, t2.ctid, t0.c0 FROM t0 CROSS JOIN t2 WHERE ((((t0.c0)IS NOT DISTINCT FROM(t2.c0)))AND((t0.c0) BETWEEN SYMMETRIC (- (t2.c0)) AND (1)));
 ctid  | ctid  | c0
-------+-------+----
 (0,1) | (0,2) |  1
 (0,1) | (0,5) |  1
 (0,4) | (0,3) |  0
 (0,4) | (0,6) |  0
(4 rows)