Re: Update takes longer than expected

On 01/09/12 1:03 PM, Andy Chambers wrote:
> I have an update that takes longer than expected and wondered if
> there's an easy way to make it go faster.
>
> It's pretty simple:-
>
> create table session (
>    id serial primary key,
>    data text);
>
> update session
>    set data = 'ipsum lorem...'
>    where id = 5;
>
> The "ipsum lorem.." stuff is an encrypted session variable from a
> rails app that does tend to get quite large
>
> select avg(length(data)) from session
> =>  31275
>
> We're trying to migrate the app from mysql to pg and this is one of
> the performance bottle-necks.  Unfortunately it slows down every
> request by about 5 seconds.  MySQL (both MyISAM and InnoDB) does this
> almost instantaneously.


is that 5 seconds for ONE of those UPDATEs, or is your webapp making
100s of those updates for every web request?



--
john r pierce                            N 37, W 122
santa cruz ca                         mid-left coast