| From: | Greg Nancarrow <gregn4422(at)gmail(dot)com> |
|---|---|
| To: | Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
| Cc: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "houzj(dot)fnst(at)fujitsu(dot)com" <houzj(dot)fnst(at)fujitsu(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "tsunakawa(dot)takay(at)fujitsu(dot)com" <tsunakawa(dot)takay(at)fujitsu(dot)com>, Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: [bug?] Missed parallel safety checks, and wrong parallel safety |
| Date: | 2021-07-27 10:30:29 |
| Message-ID: | CAJcOf-cTQH=z-VCmbZrJdGMvbGW53pK5w5fsQBXFGDPcRgv+MQ@mail.gmail.com |
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On Tue, Jul 27, 2021 at 3:58 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> IMHO, for a non-partitioned table, we should be default allow the
> parallel safely checking so that users don't have to set it for
> individual tables, OTOH, I don't think that there is any point in
> blocking the syntax for the non-partitioned table, So I think for the
> non-partitioned table if the user hasn't set it we should do automatic
> safety checking and if the user has defined the safety externally then
> we should respect that. And for the partitioned table, we will never
> do the automatic safety checking and we should always respect what the
> user has set.
>
Provided it is possible to distinguish between the default
parallel-safety (unsafe) and that default being explicitly specified
by the user, it should be OK.
In the case of performing the automatic parallel-safety checking and
the table using something that is parallel-unsafe, there will be a
performance degradation compared to the current code (hopefully only
small). That can be avoided by the user explicitly specifying that
it's parallel-unsafe.
Regards,
Greg Nancarrow
Fujitsu Australia
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