On Tue, Dec 22, 2015 at 4:14 AM, Dilip Kumar <dilipbal...@gmail.com> wrote: > On Fri, Dec 18, 2015 at 8:47 PM Robert Wrote, >>> Yes, you are right, that create_gather_path() sets parallel_safe to false >>> unconditionally but whenever we are building a non partial path, that >>> time >>> we should carry forward the parallel_safe state to its parent, and it >>> seems >>> like that part is missing here.. > >>Ah, right. Woops. I can't exactly replicate your results, but I've >>attempted to fix this in a systematic way in the new version attached >>here (parallel-join-v3.patch). > > I Have tested with the latest patch, problem is solved.. > > During my testing i observed one more behaviour in the hash join, where > Parallel hash join is taking more time compared to Normal hash join,
I think the gather-reader-order patch will fix this. Here's a test with all three patches. rhaas=# SET max_parallel_degree=0;SELECT count(*) FROM t1 JOIN t2 ON t1.c1 = t2.c1 AND t2.c2 + t1.c1 > 100; SET Time: 0.192 ms count --------- 2999950 (1 row) Time: 11331.425 ms rhaas=# SET max_parallel_degree=1;SELECT count(*) FROM t1 JOIN t2 ON t1.c1 = t2.c1 AND t2.c2 + t1.c1 > 100; SET Time: 0.185 ms count --------- 2999950 (1 row) Time: 8796.190 ms rhaas=# SET max_parallel_degree=2;SELECT count(*) FROM t1 JOIN t2 ON t1.c1 = t2.c1 AND t2.c2 + t1.c1 > 100; SET Time: 0.192 ms count --------- 2999950 (1 row) Time: 8153.258 ms rhaas=# SET max_parallel_degree=3;SELECT count(*) FROM t1 JOIN t2 ON t1.c1 = t2.c1 AND t2.c2 + t1.c1 > 100; SET Time: 0.187 ms count --------- 2999950 (1 row) Time: 6198.163 ms rhaas=# SET max_parallel_degree=4;SELECT count(*) FROM t1 JOIN t2 ON t1.c1 = t2.c1 AND t2.c2 + t1.c1 > 100; SET Time: 0.190 ms count --------- 2999950 (1 row) Time: 7511.970 ms rhaas=# SET max_parallel_degree=5;SELECT count(*) FROM t1 JOIN t2 ON t1.c1 = t2.c1 AND t2.c2 + t1.c1 > 100; SET Time: 0.152 ms count --------- 2999950 (1 row) Time: 7651.862 ms rhaas=# SET max_parallel_degree=6;SELECT count(*) FROM t1 JOIN t2 ON t1.c1 = t2.c1 AND t2.c2 + t1.c1 > 100; SET Time: 0.195 ms count --------- 2999950 (1 row) Time: 7584.073 ms -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
