Re: Performance problem with large resultsets (byte array 2200) - Mailing list pgsql-general

From Tom Lane
Subject Re: Performance problem with large resultsets (byte array 2200)
Date
Msg-id 19283.1185891945@sss.pgh.pa.us
Whole thread Raw
In response to Performance problem with large resultsets (byte array 2200)  ("Victor Adolfsson" <victor@optimumbiometrics.com>)
List pgsql-general
"Victor Adolfsson" <victor@optimumbiometrics.com> writes:
> I'm having a problem with bad performance when retrieving many rows where
> each row has a 2200 long byte array (called template_compressed) and a 50
> character varying (called uniqueid)

2200 bytes is (just) long enough to trigger toasting of the entries, and
I suppose it's the extra time to fetch a toasted value that's hurting.
As long as the total row width is under 8K, you could disable toasting
by ALTER TABLE ... SET STORAGE PLAIN on all the variable-width columns
of the table.  Note that this wouldn't in itself de-toast rows already
stored; so you'd have to dump/truncate/reload the table before seeing
any performance benefit.

            regards, tom lane

pgsql-general by date:

Previous
From: Lee Keel
Date:
Subject: Re: tables not in list
Next
From: "Nicola Benaglia"
Date:
Subject: huge file in pg_xlog and base