On Tue, 2005-10-25 at 11:18, WireSpot wrote: > On 10/25/05, Michael Fuhr <mike@xxxxxxxx> wrote: > > Are there indexes on the foreign key columns? That is, given > > the following example, > > > > CREATE TABLE foo (id integer PRIMARY KEY); > > CREATE TABLE bar (fooid integer NOT NULL REFERENCES foo ON DELETE CASCADE); > > > > do you have an index on bar.fooid? > > There are no indexes on the referring fields in any tables. Would this > make a huge difference? Yes it will. Think about it: when the delete cascades, the rows which have to be deleted in the referring table have to be found first... if there's no index, a full table scan will be done for that. An index will allow the delete process to quickly find the referring rows which have to be deleted too. So it's a good practice to create indexes on fields referring to parent tables. Cheers, Csaba. ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
