From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Andres Freund <andres(at)anarazel(dot)de>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Amit Kapila <akapila(at)postgresql(dot)org>, pgsql-committers <pgsql-committers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: pgsql: Add a new GUC and a reloption to enable inserts in parallel-mode |
Date: | 2021-03-23 20:29:58 |
Message-ID: | 20210323202958.GA18316@alvherre.pgsql |
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Lists: | pgsql-committers |
On 2021-Mar-23, Robert Haas wrote:
> Likewise, the XXX comment you added to max_parallel_hazard_walker
> claims that some of the code introduced there is to compensate for an
> unspecified bug in the rewriter. I'm a bit skeptical that the comment
> is correct, and there's no way to find out because the comment doesn't
> say what the bug supposedly is, but let's just say for the sake of
> argument that it's true. Well, you *could* have fixed the bug, but
> instead you hacked around it, and in a relatively expensive way that
> affects every query with a CTE in it whether it can benefit from this
> patch or not. That's not a responsible way of maintaining the core
> PostgreSQL code.
I think the CTE bug is this one:
while I can't disagree with the overall conclusion that it seems safer
to revert parallel INSERT/SELECT given the number of alleged problems,
it is true that this bug exists, and has gone unfixed.
--
Álvaro Herrera Valdivia, Chile
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