How reliable are the stats collector stats?

From: Eric Ridge <ebr(at)tcdi(dot)com>
To: Pgsql-General <pgsql-general(at)postgresql(dot)org>
Subject: How reliable are the stats collector stats?
Date: 2004-03-12 21:27:22
Message-ID: 0C5B8376-746C-11D8-9ADA-000A95BB5944@tcdi.com
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We've been running the stats collector for about a week now on a
heavily used production database (with all the various row/block level
gathering options enabled too). This database, in terms of number of
tables and indexes is rather large. About 100 tables, and many many
more indexes.

What we've found is that pg_stats_user_indexes shows a number indexes
that appear to be used at all (ie, zero's for idx_scan, x_tup_read, and
idx_tup_fetch columns).

Could pg_stats_user_indexes be lying? Could I be misinterpreting the
data?

I realize the real question is "why aren't these indexes being used",
but that's something I need to figure out for myself.

thanks!

eric

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