Re: Slow query needs a kick in the pants.

From: "Dann Corbit" <DCorbit(at)connx(dot)com>
To: <pgsql-general(at)postgresql(dot)org>
Subject: Re: Slow query needs a kick in the pants.
Date: 2003-03-28 01:58:24
Message-ID: D90A5A6C612A39408103E6ECDD77B829408AB7@voyager.corporate.connx.com
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The other query attempts given to me do not produce the desired results.
Thanks for taking a look anyway.

Let me explain the problem set, and what I want to accomplish...

I have two tables in all cases. Each table pair consists of the
following columns:
1. A primary key of one or more columns {with a unique index}
2. An Oid column {with a unique index}
3. A 64 bit CRC

For both tables, the primary key information will "mostly" match. I
need to know which primary keys are found in the first table but not in
the second. Also, which primary keys are found in the second table but
not in the first.

One possibility would be to add a tag column and set it where the two
tables agree on primary key. Unfortunately, we are likely to have many
millions of rows (and only a few thousand disagreements) and so I would
end up rewriting the entire table for both tables (less the tiny
difference set) and hence that would be inefficient. My outer join
also stinks up the place. (Several minutes for a million rows --
unacceptable).

Probably, I am going to have to write my own piece of custom software
that manipulates the data outside of any database. The database query
approach is just too slow.


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