RE: Consider Parallelism While Planning For REFRESH MATERIALIZED VIEW

From: "Hou, Zhijie" <houzj(dot)fnst(at)cn(dot)fujitsu(dot)com>
To: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: RE: Consider Parallelism While Planning For REFRESH MATERIALIZED VIEW
Date: 2020-12-23 03:44:30
Message-ID: 29b4a356e73241ca9ae67a851cf442bc@G08CNEXMBPEKD05.g08.fujitsu.local
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> Thanks for taking a look at the patch.
>
> The intention of the patch is to just enable the parallel mode while planning
> the select part of the materialized view, but the insertions do happen in
> the leader backend itself. That way even if there's temporary tablespace
> gets created, we have no problem.
>
> This patch can be thought as a precursor to parallelizing inserts in refresh
> matview. I'm thinking to follow the design of parallel inserts in ctas [1]
> i.e. pushing the dest receiver down to the workers once that gets reviewed
> and finalized. At that time, we should take care of not pushing inserts
> down to workers if temporary tablespace gets created.
>
> In summary, as far as this patch is considered we don't have any problem
> with temporary tablespace getting created with CONCURRENTLY option.
>
> I'm planning to add a few test cases to cover this patch in matview.sql
> and post a v2 patch soon.

Thanks for your explanation!
You are right that temporary tablespace does not affect current patch.

For the testcase:
I noticed that you have post a mail about add explain support for REFRESH MATERIALIZED VIEW.
Do you think we can combine these two features in one thread ?

Personally, The testcase with explain info will be better.

Best regards,
houzj

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