From: kolszew73@gmail.com <kolszew73@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Re: Problem with slow query with WHERE conditions with OR clause on primary keys
Date: Wed, 18 Dec 2013 11:23:21 -0800 (PST)
Message-ID: <1387394601821-5783927.post@n5.nabble.com> (raw)
In-Reply-To: <1386746318622-5782822.post@n5.nabble.com>
References: <52A7A428.8070104@gmail.com>
<1386746318622-5782822.post@n5.nabble.com>
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Thanx for your answer
My example is trivial because i want to show strange (for me) postgres
behavior with dealing with primary keys (extreme example), in real situation
user put search condition e.g. "Panas" and this generates query
...
where gd.other_code like 'Panas%' OR g.code like 'Panas%'
..
both columns has very good indexes and selectivity for "like 'Panas%'" ...
I have experience from Oracle with this type of queries, and Oracle have no
problem with it,
executes select on index on other_code from gd and join g
in next step executes select on index on code from g and join gd
and this two results are connected in last step (like union)
very fast on minimal cost
and in my opinion read whole huge tables only for 10 rows in result where
conditions are very good ... is strange
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To: pgsql-performance@postgresql.org
Cc: kolszew73@gmail.com
Subject: Re: Problem with slow query with WHERE conditions with OR clause on primary keys
In-Reply-To: <1387394601821-5783927.post@n5.nabble.com>
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