Re: Very slow catalog query

Hi Tom,

> Well, it's hard to be sure what the problem is when you're not showing
> us a problem case ... but I notice that this indexscan is estimated
> awfully high:

Whenever I do it manually it works fast. But in the log I see lots of
slow ones. Could it be caused by auto vacuum? Or by check pointing or
WAL writing? Are there way to check that?

> > -> Index Scan using
> > pg_depend_reference_index on pg_depend dep (cost=0.00..64942.17
> > rows=247 width=12) (actual time=396.542..1547.172 rows=22 loops=1)
> > Index Cond: (refobjid = 30375069::oid)
>
> The reason is not far to seek: the scan is checking only the second
> index key, meaning that it has to scan the entire index. (I am
> surprised it didn't use a seqscan instead. Are you using enable_seqscan
> = off? Not a great idea.) Since you know you are looking for a table,
> you could improve matters by adding a constraint on refclassid:
>
> dep.refclassid = 'pg_class'::regclass

enable_setscan is on. Is there a way to analyze/vacuum those tables?

I will look if I can also improve the query to be more exact.

Bye,

Guy.