Re: Effect of large text field data on queries

From: Glen Parker <glenebob(at)nwlink(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Postgres General <pgsql-general(at)postgresql(dot)org>
Subject: Re: Effect of large text field data on queries
Date: 2006-10-26 20:32:26
Message-ID: 45411B5A.9040905@nwlink.com
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Tom Lane wrote:
> Glen Parker <glenebob(at)nwlink(dot)com> writes:
>> Why would very large text values effect the speed of a seq scan that
>> does not actually evaluate those values?
>
> I'd actually suppose it's the smaller values (up to a few hundred bytes)
> that impact this the most. Really wide fields would be pushed
> out-of-line.

Meaning that the portion of the text value stored in the companion TOAST
table would be ignored for this type of query, correct? That's why I'm
concerned.

How much of a TOAST'd field is actually stored in the main heap table?
Is there a way to configure that amount?

-Glen

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