From: Andreas Kretschmer <andreas@a-kretschmer.de>
To: Ilija Vidoevski <ilija.vidoevski@yahoo.com>; "pgsql-novice@postgresql.org" <pgsql-novice@postgresql.org>
Sent: Monday, July 30, 2012 8:04 PM
Subject: Re: [NOVICE] very slow update query
Ilija Vidoevski <
ilija.vidoevski@yahoo.com> hat am 30. Juli 2012 um 19:50
geschrieben:
> I need to update one table in my database with simple code
> This is the script
>
> update finarh
> set vid = left(nalog,1)
>
> Table has 177714 rows.
>
> First execution time was : 00:02:39 minutes
> Repeated execution time: 00:01:03 minutes.
>
> Explain query plan is:
> "Update on finarh (cost=0.00..12049.99 rows=177714 width=172)"
> " -> Seq Scan on finarh (cost=0.00..12049.99 rows=177714 width=172)"
>
> Why execution time is so loooong ?
>
>
The database rewrite the whole table, 177 thousand records, this takes some
time...
Why you are doing that? the column vid are redundant, you should better use
select left(nalog,1) as vid and drop that vid-column from the table.
Regards, Andreas
>
>