From: | "Merlin Moncure" <mmoncure(at)gmail(dot)com> |
---|---|
To: | "Arturo Perez" <aperez(at)hayesinc(dot)com> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Adding TEXT columns tanks performance? |
Date: | 2007-02-09 16:43:02 |
Message-ID: | b42b73150702090843m5932faa7pb8ec7feafb9e450b@mail.gmail.com |
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Lists: | pgsql-general |
On 2/8/07, Arturo Perez <aperez(at)hayesinc(dot)com> wrote:
> Hi all,
>
> Saturday I changed a table to add a varchar(24) and a TEXT column.
> It's used for some reporting purposes (small potatoe stuff really)
> and the TEXT column remains mostly empty. However, this week
> performance has gotten terrible. Queries joining against the
> aforementioned table have gone from 40s to 1500s. The schema change
> is the only explanation I have for the 30x slower queries. The
> queries have definitely gotten disk-bound (I can see the connection
> process sitting in the D state for several minutes).
>
> This is pg8.1.4 on Linux RedHat. Would adding a TEXT column impact
> things that much? The change to the schema was
>
> alter table foo add column title text;
explain analyze please.
no reason for adding text column to do that. especially since you
didn't default the column which would effectively update the entire
table.
merlin
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