Re: Update

In article <6nq0i4$i0l$1@news.Leiden.NL.net>, Albert Wisse <wissea@cayennesoft.com> writes >I have the following situation: > >I have seen when tracing an application the following update statement(s), >by example > >update table01 > set (a, b) = ('xxx', 'yyyy') > where a = 'xxx' > >On column a exists an unique index. > >I wondered why the application updates the column on which its selects. > >If I am not mistaken is updating the a column (very) bad for performance >there the unique constraint has to verified, locks live longer, etc. >My question is, is their more to tell about this kind of update, to help my >to convince the designer to alter the update statements such as a higher >chance on deadlocks, lock time-outs etc. > Perhaps the user can change a but in this instance decided not to. Always updating all columns is simpler to code and test. reliability vs performance.. > >The Informix version 7.20.UC2 > >Regards, > >Albert Wisse > > -- David Williams Maintainer of the Informix FAQ Primary site (Beta Version) http://www.smooth1.demon.co.uk Official site http://www.iiug.org/techinfo/faq/faq_top.html I see you standin', Standin' on your own, It's such a lonely place for you, For you to be If you need a shoulder, Or if you need a friend, I'll be here standing, Until the bitter end... So don't chastise me Or think I, I mean you harm... All I ever wanted Was for you To know that I care