Re: Extremely Slow Cascade Delete Operation

OMG, I never know what is index (Sorry for my newbies) I will study about them and update you all about their performance.

Thanks and Regards
Yan Cheng CHEOK

--- On Wed, 1/13/10, Craig Ringer <craig(at)postnewspapers(dot)com(dot)au> wrote:

> From: Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>
> Subject: Re: [GENERAL] Extremely Slow Cascade Delete Operation
> To: "Yan Cheng Cheok" <yccheok(at)yahoo(dot)com>
> Cc: pgsql-general(at)postgresql(dot)org
> Date: Wednesday, January 13, 2010, 7:01 PM
> On 13/01/2010 4:09 PM, Yan Cheng
> Cheok wrote:
> > I have 3 tables - lot, unit and measurement
> >
> > 1 lot is having relationship to many unit.
> > 1 unit is having relationship to many measurement.
> > delete cascade is being used among their relationship
> >
>
> > SemiconductorInspection=# delete from lot where lot_id
> = 2;
>
> Are there indexes on fk_lot_id and fk_unit_id ? If not, a
> DELETE from lot will cause a seqscan of unit for affected
> units, and if any must be deleted each will cause a seqscan
> of measurement for affected measurements. That's going to
> get ugly fast.
>
> --
> Craig Ringer
>
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