Re: Parallel Bitmap scans a bit broken

From: Dilip Kumar <dilipbalaut(at)gmail(dot)com>
To: Emre Hasegeli <emre(at)hasegeli(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Parallel Bitmap scans a bit broken
Date: 2017-03-15 23:41:17
Message-ID: CAFiTN-sGFLaHoPrERof6XohJjTcPx+xXRkyFKE_md-asN=V46A@mail.gmail.com
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On Thu, Mar 16, 2017 at 5:02 AM, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> After above fix, I am not able to reproduce. Can you give me the
> backtrace of the crash location or the dump?
>
> I am trying on the below commit
>
> commit c5832346625af4193b1242e57e7d13e66a220b38
> Author: Stephen Frost <sfrost(at)snowman(dot)net>
> Date: Wed Mar 15 11:19:39 2017 -0400
>
> + https://www.postgresql.org/message-id/attachment/50164/brin-correlation-v3.patch
> + fix_tbm_empty.patch

Forgot to mention after fix I am seeing this output.

postgres=# explain analyze select * from only r2 where i = 10;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------
Gather (cost=2880.56..9251.98 rows=1 width=4) (actual
time=3.857..3.857 rows=0 loops=1)
Workers Planned: 2
Workers Launched: 2
-> Parallel Bitmap Heap Scan on r2 (cost=1880.56..8251.88 rows=1
width=4) (actual time=0.043..0.043 rows=0 loops=3)
Recheck Cond: (i = 10)
-> Bitmap Index Scan on r2_i_idx (cost=0.00..1880.56
rows=373694 width=0) (actual time=0.052..0.052 rows=0 loops=1)
Index Cond: (i = 10)
Planning time: 0.111 ms
Execution time: 4.449 ms
(9 rows)

postgres=# select * from only r2 where i = 10;
i
---
(0 rows)

Are you getting the crash with the same test case?

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

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