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why does this query not use a parallel query 2+ messages / 2 participants [nested] [flat]
* why does this query not use a parallel query @ 2018-03-02 16:29 Dave Cramer <davecramer@gmail.com> 0 siblings, 1 reply; 2+ messages in thread From: Dave Cramer @ 2018-03-02 16:29 UTC (permalink / raw) To: pgsql-performance Have a query: explain analyze SELECT minion_id FROM mob_player_mob_118 WHERE player_id = 55351078; QUERY PLAN --------------------------------------------------------------------------------------------------------------------------------------------------------------------- Index Only Scan using mob_player_mob_118_pkey on mob_player_mob_118 (cost=0.44..117887.06 rows=4623076 width=4) (actual time=0.062..3716.105 rows=4625123 loops=1) Index Cond: (player_id = 55351078) Heap Fetches: 1152408 Planning time: 0.241 ms Execution time: 5272.171 ms If I just get the count it will use a parallel query explain analyze SELECT count(minion_id) FROM mob_player_mob_118 WHERE player_id = 55351078; Thanks Dave Cramer ^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: why does this query not use a parallel query @ 2018-03-02 16:44 Tom Lane <tgl@sss.pgh.pa.us> parent: Dave Cramer <davecramer@gmail.com> 0 siblings, 0 replies; 2+ messages in thread From: Tom Lane @ 2018-03-02 16:44 UTC (permalink / raw) To: Dave Cramer <davecramer@gmail.com>; +Cc: pgsql-performance Dave Cramer <davecramer@gmail.com> writes: > Have a query: > explain analyze SELECT minion_id FROM mob_player_mob_118 WHERE player_id = > 55351078; > Index Only Scan using mob_player_mob_118_pkey on mob_player_mob_118 > (cost=0.44..117887.06 rows=4623076 width=4) (actual time=0.062..3716.105 > rows=4625123 loops=1) I don't think we have parallel IOS yet (I might be wrong). If so, it probably thinks this is cheaper than the best available parallel plan. > If I just get the count it will use a parallel query Likely a parallelized aggregation. regards, tom lane ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2018-03-02 16:44 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2018-03-02 16:29 why does this query not use a parallel query Dave Cramer <davecramer@gmail.com> 2018-03-02 16:44 ` Tom Lane <tgl@sss.pgh.pa.us>
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