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Re: Problems with adding a is not null to a query.

From: Tim Uckun <timuckun(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: Problems with adding a is not null to a query.
Date: 2011-01-17 22:14:06
Message-ID: AANLkTinD_Bmgy34W70ywxXM0b1xOWBBEvR8hO95y9LzS@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-bugs
> With a table that large, you're probably going to need a larger stats
> target in order to get reasonable estimates for low-frequency values.
> Am I right in guessing that pg_stats.n_distinct is much too low for
> the domain_id column?

the domain_id is in the topical urls. A select count of domains shows
that there are 700 domains, the pg_stats shows 170 which seems kind of
low but maybe is not out of bounds because most domains are probably
inactive.


pg_stats on the consolidated_urls table shows a very low value for
index_delta. There are 1.8 million records and the n_distinct for
index_delta is 151.  It's a floating point number so that seems weird.
For index it's 818.

Both of those numbers are wildly wrong I would think.

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Subject: Re: Problems with adding a is not null to a query.
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