Subject: Re: Less than ideal error reporting in pg_stat_statements
To: Peter Geoghegan <pg@heroku.com>
References: <5601D354.5000703@BlueTreble.com>
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From: Jim Nasby <Jim.Nasby@BlueTreble.com>
Message-ID: <5601E3D1.5010401@BlueTreble.com>
Date: Tue, 22 Sep 2015 18:27:13 -0500
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On 9/22/15 5:58 PM, Peter Geoghegan wrote:
> On Tue, Sep 22, 2015 at 3:16 PM, Jim Nasby <Jim.Nasby@bluetreble.com> wrote:
>> At first I thought the lack of context indicated a palloc had failed during
>> ereport() (since we apparently just toss the previous error when that
>> happens), but it turns out there's some error reporting in
>> pg_stat_statements that's less than ideal. Attached patch fixes, though I'm
>> not sure if %lld is portable or not.
>
> + ereport(LOG,
> +              (errcode(ERRCODE_OUT_OF_MEMORY),
> +               errmsg("out of memory attempting to pg_stat_statement file"),
> +               errdetail("file \"%s\": size %lld", PGSS_TEXT_FILE,
> stat.st_size)));
>
> Uh, what?

Oops. I'll fix that and address David's concern tomorrow.

> I'm not opposed to this basic idea, but I think the message should be
> reworded, and that the presence of two separate ereport() call sites
> like the above is totally unnecessary. The existing MaxAllocSize check
> is just defensive; no user-visible distinction needs to be made.

I disagree. If you're running this on a 200+GB machine with plenty of 
free memory and get that error you're going to be scratching your head. 
I can see an argument for using the OOM SQLSTATE, but treating an 
artificial limit the same as a system error seems pretty bogus.
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com


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