To: "Joshua D. Drake" <jd@commandprompt.com>
cc: Michael Paesold <mpaesold@gmx.at>, NikhilS <nikkhils@gmail.com>,
	David Fetter <david@fetter.org>,
	"Jonah H. Harris" <jonah.harris@gmail.com>,
	PostgreSQL Docs <pgsql-docs@postgresql.org>,
	PostgreSQL Patches <pgsql-patches@postgresql.org>
Subject: Re: [PATCHES] Partition: use triggers instead of rules 
In-reply-to: <474EE25E.3080304@commandprompt.com> 
References: <20071128202615.GG24146@fetter.org>
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	<20071129031702.GU24146@fetter.org> <2854.1196315753@sss.pgh.pa.us>
	<20071128224154.06f950c9@commandprompt.com>
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Comments: In-reply-to "Joshua D. Drake" <jd@commandprompt.com>
	message dated "Thu, 29 Nov 2007 08:01:34 -0800"
Date: Thu, 29 Nov 2007 11:17:25 -0500
Message-ID: <14455.1196353045@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

"Joshua D. Drake" <jd@commandprompt.com> writes:
> Rules are extremely slow in comparisons and not anywhere near as 
> flexible. As I said up post yesterday... they work well in the basic 
> partitioning configuration but anything else they are extremely deficient.

I think that the above claim is exceedingly narrow-minded.  A trigger
will probably beat a rule for inserts/updates involving a small number
of rows.  For large numbers of rows, like an INSERT/SELECT from another
large table, the rule is likely to win, because its overhead is paid
once per query not once per row.  Also, if you implement the trigger
with an EXECUTE (forcing a planning cycle) intead of hard-coded
commands, the speed advantage becomes even more dubious.

			regards, tom lane