From: | "houzj(dot)fnst(at)fujitsu(dot)com" <houzj(dot)fnst(at)fujitsu(dot)com> |
---|---|
To: | Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, "tsunakawa(dot)takay(at)fujitsu(dot)com" <tsunakawa(dot)takay(at)fujitsu(dot)com> |
Cc: | "tanghy(dot)fnst(at)fujitsu(dot)com" <tanghy(dot)fnst(at)fujitsu(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Zhihong Yu <zyu(at)yugabyte(dot)com>, Luc Vlaming <luc(at)swarm64(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
Subject: | RE: Parallel Inserts in CREATE TABLE AS |
Date: | 2021-05-27 11:11:59 |
Message-ID: | OS0PR01MB5716E05057BEAE757E8FBDF694239@OS0PR01MB5716.jpnprd01.prod.outlook.com |
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Lists: | pgsql-hackers |
From: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
Sent: Thursday, May 27, 2021 3:41 PM
>
> On Thu, May 27, 2021 at 1:03 PM tsunakawa(dot)takay(at)fujitsu(dot)com
> <tsunakawa(dot)takay(at)fujitsu(dot)com> wrote:
> >
> > From: houzj(dot)fnst(at)fujitsu(dot)com <houzj(dot)fnst(at)fujitsu(dot)com>
> > > Although, the 4 workers case still has performance degradation
> > > compared to serial case.
> > >
> > > SERIAL: 58759.213 ms
> > > PARALLEL 2 WORKER [NOT SKIP FSM]: 68390.221 ms [SKIP FSM]:
> > > 58633.924 ms
> > > PARALLEL 4 WORKER [NOT SKIP FSM]: 67448.142 ms [SKIP FSM]:
> > > 66,960.305 ms
> >
> > Can you see any difference in table sizes?
>
> Also, the number of pages the table occupies in each case along with table size
> would give more insights.
>
> I do as follows to get the number of pages a relation occupies:
> CREATE EXTENSION pgstattuple;
> SELECT pg_relpages('test');
It seems the difference between SKIP FSM and NOT SKIP FSM is not big.
I tried serval times and the average result is almost the same.
pg_relpages
-------------
1428575
pg_relation_size
-------------
11702976512(11G)
Best regards,
houzj
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