On 2016/06/20 15:42, Amit Kapila wrote: > On Mon, Jun 20, 2016 at 11:48 AM, Masahiko Sawada <sawada.m...@gmail.com> > wrote: >> >> Hi all, >> >> My colleague noticed that the output of EXPLAIN ANALYZE doesn't work >> fine for parallel seq scan. >>
[ ... ] >> For example, the above result shows, >> Parallel Seq Scan : actual rows = 3333333 >> worker 0 : actual rows = 3457968 >> worker 1 : actual rows = 3741069 >> Summation of these is 10532370, but actual total rows is 10000000. >> I think that Parallel Seq Scan should show actual rows = >> 10000000(total rows) or actual rows = 2800963(rows collected by >> itself). (10000000 maybe better) >> > > You have to read the rows at Parallel Seq Scan nodes as total count of > rows, but you have to consider the loops parameter as well. > >> >> After spent time to investigate this behaviour, ISTM that the problem >> is nloops of Parallel Seq Scan. >> Parallel Seq Scan is done only once, but nloops is incremented to 3. >> > > nloops here indicates, that it is done for 2 workers and a master backend. Does the way parallel instrumentation info is currently handled allow to also show the leader's info maybe like below: -> Parallel Seq Scan on public.pgbench_accounts (cost=0.00..205601.67 rows=4166667 width=0) (actual time=0.042..1685.542 rows=3333333 loops=3) Leader: actual time=x.xxx..xxxx.xxx rows=2800963 loops=1 Worker 0: actual time=0.033..1657.486 rows=3457968 loops=1 Worker 1: actual time=0.039..1702.979 rows=3741069 loops=1 Thanks, Amit -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers