From: Kevin Grittner <kgrittn@mail.com>
To: sthomas@optionshouse.com,"Tom Lane" <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: Setting Statistics on Functional Indexes
Date: Mon, 29 Oct 2012 14:51:14 -0400
Message-ID: <20121029185114.79490@gmx.com> (raw)
Shaun Thomas wrote:
> I know that current_date seems like an edge case, but I can't see
> how getting the most recent activity for something is an uncommon
> activity. Tip tracking is actually the most frequent pattern in the
> systems I've seen.
Yeah, this has been a recurring problem with database statistics
with various products for at least 20 years. For a while I was using
a product whose optimizer engineers referred to it as "data skew" and
recommended adding a "dummy" entry to get a single value out past the
maximum end of the range. If you couldn't stomach the dummy data,
they had detailed instructions for dumping your statistics, tinkering
with the end of it to allow for the issue, and writing it back over
the actual statistics gathered. We need a better answer than that.
> I just wonder if this particular tweak isn't more of a regression
> than initially thought.
It does seem like we have a serious regression in terms of this
particular issue.
-Kevin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: kgrittn@mail.com, tgl@sss.pgh.pa.us
Subject: Re: Setting Statistics on Functional Indexes
In-Reply-To: <20121029185114.79490@gmx.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox