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From: Pavel Stehule <[email protected]>
To: Tom Lane <[email protected]>
Cc: Shaozhong SHI <[email protected]>
Cc: pgsql-sql <[email protected]>
Subject: Re: Memory allocation error
Date: Fri, 14 Jul 2023 13:54:17 +0200
Message-ID: <CAFj8pRCLpzCrGBk-i7ZQm+jKdiqJZQrj1Vt_KbvhwWqFqN7sRQ@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
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	<[email protected]>

pá 14. 7. 2023 v 13:13 odesílatel Tom Lane <[email protected]> napsal:

> Pavel Stehule <[email protected]> writes:
> > pá 14. 7. 2023 v 9:36 odesílatel Shaozhong SHI <[email protected]>
> > napsal:
> >> On Fri, 14 Jul 2023 at 08:14, Pavel Stehule <[email protected]>
> >> wrote:
> >>> It depends what you do. Postgres doesn't allow to allocate bigger
> blocks
> >>> than 1GB. Maybe you create too big string or too big value of some
> other
> >>> type. But it can be signal of some cache bloating.
>
> > The best way - do it all in one recursive query without any recursive
> > function.
> > This issue you can fix only by rewriting your code.
>
> Yeah, but nonetheless this error message is pretty user-unfriendly.
>
> The given example is too incomplete to run as-is, but I guessed that
> maybe the array_agg() was accumulating too many values, and sure
> enough it's possible to reproduce:
>
> regression=# select array_agg(x::text) from generate_series(1,100000000) x;
> ERROR:  invalid memory alloc request size 1073741824
>
> We can do better than that.  The attached patch causes the error to be
>
> regression=# select array_agg(x::text) from generate_series(1,100000000) x;
> ERROR:  array size exceeds the maximum allowed (1073741823)
>

+1

it is significantly better

Regards

Pavel

>
> I'm not wedded to that wording, but it's an existing translatable string
> that at least points you in the direction of "my array is too big".
> (This is also what you get if the eventual array construction overruns
> the 1G limit, cf construct_md_array().)
>
>                         regards, tom lane
>
>


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