From: | "Mason Hale" <masonhale(at)gmail(dot)com> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Hash Aggregate plan picked for very large table == out of memory |
Date: | 2007-06-14 21:09:42 |
Message-ID: | 8bca3aa10706141409oa6ddc6fk305b446f45229bba@mail.gmail.com |
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Lists: | pgsql-general |
I should have mentioned this previously: running the same query against the
same data on 8.1.5 does not result in a hash aggregate plan or an out of
memory error. (Note: the hardware is different but very similar -- the main
difference is the 8.1.9 server (with the error) has faster disks)
On 6/14/07, Mason Hale <masonhale(at)gmail(dot)com> wrote:
>
> Thanks Tom. Here's more info:
>
> What have you got work_mem set to?
>
>
> 40960
>
> What's the actual number of groups
> > (target_page_id values)?
>
>
> Approximately 40 million (I'll have a more precise number when the query
> finishes running ).
>
> Maybe this helps?
>
> crystal=> select null_frac, n_distinct, correlation from pg_stats where
> tablename = 'page_page_link' and attname = 'target_page_id';
> null_frac | n_distinct | correlation
> -----------+------------+-------------
> 0 | 550017 | 0.240603
> (1 row)
>
> Mason
>
>
>
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