Re: Extremely Slow Cascade Delete Operation

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