Re: slow update but have an index - Mailing list pgsql-general

From Martijn van Oosterhout
Subject Re: slow update but have an index
Date
Msg-id 20010817201255.B20613@svana.org
Whole thread Raw
In response to slow update but have an index  (Feite Brekeveld <feite.brekeveld@osiris-it.nl>)
List pgsql-general
On Fri, Aug 17, 2001 at 01:08:29PM +0200, Feite Brekeveld wrote:
> Now this table has about 80,000 records. I need to update 74,000 status
> fields. So I made a dump, and hacked the dump into SQL statements like:
>
> update accounting set status = 'C' where seqno = 1566385;
> ....
> and the other 74,000
>
> This is awfully slow. How come ? The index on the seqno should give
> speedy access to the record.

Well, an index speeds it up, but that times 80,000 will still take a while.
Is there any trickery or will this work?

update accounting set status = 'C';

If so, that will be much faster.

One sequential scan is faster than 80,000 index scans.

--
Martijn van Oosterhout <kleptog@svana.org>
http://svana.org/kleptog/
> It would be nice if someone came up with a certification system that
> actually separated those who can barely regurgitate what they crammed over
> the last few weeks from those who command secret ninja networking powers.

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