[GPU Logic Bug] SELECT <column> FROM <table> WHERE <column> BETWEEN SYMMETRIC <number> AND <column> Brings GPU Logic Bug

[qwebug]

Describe:

SELECT <column> FROM <table> WHERE <column> BETWEEN SYMMETRIC <number> AND <column> brings different results, when using CPU-only configurations and GPU-used configurations.

SQL with CPU-only Config:

CREATE TABLE t0(c0 INT);
CREATE TABLE t1(c0 INT) INHERITS(t0);
INSERT INTO t0(c0) VALUES(1);
INSERT INTO t1(c0) VALUES(1);
CREATE SCHEMA extensions;
CREATE EXTENSION pg_strom WITH SCHEMA extensions;
SET pg_strom.enabled=off;
SELECT t1.c0 FROM t0, t1 WHERE (t1.c0) BETWEEN SYMMETRIC (1) AND (t0.c0);

Result:

 c0 
----
  1
  1
(2 rows)

SQL with GPU-used Config:

SET pg_strom.enabled=on;
SELECT t1.c0 FROM t0, t1 WHERE (t1.c0) BETWEEN SYMMETRIC (1) AND (t0.c0);

Result:

 c0 
----
  1
(1 row)

Environment:

Pg-strom Version: commit 9765660

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]

a5cd19492825a270a7f6f0fb266a0f37622fcec1 fixed the problem.

For more precise, it just avoid to add GPU-paths on the inheritanced tables because most people use table partitioning nowadays, and it covers most of use cases PG-Strom wants to cover. So, it is not a good idea to cover the traditional table inheritances also from now.

postgres=# EXPLAIN SELECT t1.c0 FROM t0, t1 WHERE (t1.c0) BETWEEN SYMMETRIC (1) AND (t0.c0);
                                                       QUERY PLAN
------------------------------------------------------------------------------------------------------------------------
 Custom Scan (GpuJoin) on t1  (cost=102.07..103.08 rows=1 width=4)
   GPU Projection: t1.c0
   GPU Scan Quals: ((t1.c0 >= 1) OR (t1.c0 <= 1)) [rows: 1 -> 1]
   GPU Join Quals [1]: (((t1.c0 >= 1) AND (t1.c0 <= t0.c0)) OR ((t1.c0 >= t0.c0) AND (t1.c0 <= 1))) ... [nrows: 1 -> 1]
   GPU-Direct SQL: enabled (N=2,GPU0,1)
   ->  Append  (cost=0.00..2.03 rows=2 width=4)
         ->  Seq Scan on t0 t0_1  (cost=0.00..1.01 rows=1 width=4)
         ->  Seq Scan on t1 t0_2  (cost=0.00..1.01 rows=1 width=4)
(8 rows)

postgres=# SELECT t1.c0 FROM t0, t1 WHERE (t1.c0) BETWEEN SYMMETRIC (1) AND (t0.c0);
 c0
----
  1
  1
(2 rows)