From: Andreas Pflug <pgadmin@pse-consulting.de>
To: Stephan Szabo <sszabo@megazone.bigpanda.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [GENERAL] 7.4Beta
Date: Fri, 15 Aug 2003 17:33:21 +0200
Message-ID: <3F3CFD41.7020508@pse-consulting.de> (raw)
In-Reply-To: <20030815073521.B19338-100000@megazone.bigpanda.com>
References: <20030815073521.B19338-100000@megazone.bigpanda.com>
Stephan Szabo wrote:
>On Fri, 15 Aug 2003, Andreas Pflug wrote:
>
>
>
>>Stephan Szabo wrote:
>>
>>
>>
>>>That really needs to be rewritten to do a single check over the table
>>>rather than running the constraint for every row. I keep meaning to get
>>>around to it and never actually do. :( I'm not sure that in practice
>>>you'll get a better plan at restore time depending on what the default
>>>statistics give you.
>>>
>>>
>>>
>>This is clearly a case for a statement level trigger, as soon as
>>affected rows can be identified.
>>
>>
>
>Well, I think single inserts might be more expensive (because the query is
>more involved for the table joining case) using a statement level trigger,
>so we'd probably want to profile the cases.
>
>
This really depends. If a constraint is just a check on the
inserted/updated column, so no other row needs to be checked, there's no
faster way then the current row trigger. But FK constraints need to
execute a query to retrieve the referenced row, and every RDBMS prefers
to execute a single statement with many rows over many statements with a
single row, because the first will profit from optimization. And even if
only a single row is inserted or updated, there's still the need to
lookup the reference.
Regards,
Andreas
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To: pgsql-hackers@postgresql.org
Cc: pgadmin@pse-consulting.de, sszabo@megazone.bigpanda.com
Subject: Re: [GENERAL] 7.4Beta
In-Reply-To: <3F3CFD41.7020508@pse-consulting.de>
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