Re: finding unused indexes?

resurrecting an old thread:

so is it safe to say that an index that has
pg_stat_user_indexes.idx_scan, pg_stat_user_indexes.idx_tup_read, and
pg_stat_user_indexes.idx_tup_fetch all equal to 0 has not been used
(since stats have been reset)?

i have a bunch of those and all of them have
pg_statio_user_indexes.idx_blks_read > 0 and most of those have
pg_statio_user_indexes.idx_blks_hit > 0. when/why would that happen? i
guess i don't entirely understand those two values so an explanation
would be very welcome (maybe an example of when each of the five values
gets incremented.

thanks!

george

> -----Original Message-----
> From: Brad Nicholson [mailto:bnichols(at)ca(dot)afilias(dot)info]
> Sent: Tuesday, August 01, 2006 9:12 AM
> To: George Pavlov
> Cc: pgsql-sql(at)postgresql(dot)org
> Subject: Re: [SQL] finding unused indexes?
>
> On Tue, 2006-08-01 at 09:05 -0700, George Pavlov wrote:
> > Anybody have a clever way to quickly find whether there are
> any unused
> > indexes in a PG DB? One way I have done is to take queries
> from the DB
> > log, prepend an explain to each and grep the results, but I
> am wondering
> > if there are either any index usage stats maintained
> somewhere inside
> > Postgres or if there is a slicker/less cumbersome way of
> doing it. Also
> > indexes used by functions are hard to simulate that way.
>
>
> Check out pg_stat_user_indexes, pg_stat_sys_indexes and
> pg_statio_all_indexes
>
> You can very clearly see the index usage there. You might
> have to mess
> with the statistics collector section in the postgresql.conf file in
> order to collect the information.
>
> Brad.