Re: Interpreting statistics collector output

On Wed, Aug 08, 2007 at 11:01:13AM -0400, Steve Madsen wrote:
> Can anyone provide a brief overview of how to go about interpreting
> the information generated by the statistics collector? I've looked
> around and can't find old mailing list messages or anything in the
> manual beyond the basics of how to query the statistics.
>
> Cache hit rates are easy to compute, but is this useful beyond
> knowing if Postgres has enough buffers?
>
> Can anything useful be gleaned from looking at idx_scan /
> idx_tup_read / idx_tup_fetch?

Yes, that will give you information about how often an index is being
used. If you see indexes where idx_scan is a small number, that's an
indication that that index isn't being used for queries and could
potentially be dropped.

Something else I like to look at is pg_stat_all_tables seq_scan and
seq_tup_read. If seq_scan is a large number and seq_tup_read/seq_scan is
also large, that indicates that you could use an index on that table.
--
Decibel!, aka Jim Nasby decibel(at)decibel(dot)org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)