From: | Tom Duffey <tduffey(at)trillitech(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Query memory usage |
Date: | 2010-05-16 01:05:16 |
Message-ID: | 911E621A-0474-421F-9CD1-C17F1AB3DB31@trillitech.com |
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Lists: | pgsql-general |
On May 15, 2010, at 8:00 PM, Tom Lane wrote:
> Tom Duffey <tduffey(at)trillitech(dot)com> writes:
>> On May 15, 2010, at 7:28 PM, Tom Lane wrote:
>>> Well, I tried executing a large "copy (select ...)" query and
>>> couldn't
>>> see any memory bloat at all in either the backend or psql. So
>>> there's
>>> something relevant that you haven't told us.
>
>> I hope you are right! The actual query is different because I was
>> not
>> aware until right before I posted this question that you can have a
>> WHERE clause with COPY. Here is the actual query I ran:
>
>> SELECT point_id || E'\t' || status || E'\t' || value || E'\t' ||
>> timestamp
>> FROM point_history
>> WHERE timestamp > NOW() - interval '18 months';
>
> Ermm ... is that the whole query, or did you wrap it in COPY (...) TO
> STDOUT? The former case will cause psql to eat memory, because it
> tries
> to buffer the whole result of an ordinary query. In the latter case
> psql will just stream the data through to the output file.
That's the whole query. If I understand your reply correctly it
sounds like psql was the culprit and that I should try again using
COPY (...) TO STDOUT, no?
Tom
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