On Thu, Nov 12, 2015 at 7:12 AM, Merlin Moncure <mmonc...@gmail.com> wrote:
> On Wed, Nov 11, 2015 at 1:33 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > > Massalin Yerzhan <yerz...@gmail.com> writes: > >> I'm having an issue. The query never ends: > >> delete from bb_gamelist_league; > > > > 9 times out of 10, the answer to this type of problem is that you have > > some table referencing this one by a foreign key, and the referencing > > column is not indexed. PG doesn't require such an index, but lack of > > one will mean that retail checks or deletions of referencing rows are > > really slow. > > > > If you're not sure which table is the problem, try doing an EXPLAIN > > ANALYZE of a DELETE that will only remove a few rows. You should > > see some time blamed on a trigger associated with the FK constraint. > > You've answered this question (with the same answer) what feels like a > gazillion times. I guess the underlying problem is that EXPLAIN is, > uh, not explaining things very well. > What about a warning on creation? db=> create table foo(i integer primary key); db=> create table bar(j integer primary key, i integer); db=> alter table bar add constraint fk_bar foreign key(i) references foo(i); WARNING: fk_bar: column bar(i) has no index, deletions on table foo may be slow. It might save some fraction of these questions. Craig > > merlin > > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance > -- --------------------------------- Craig A. James Chief Technology Officer eMolecules, Inc. ---------------------------------
