From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeff Janes <jeff.janes@gmail.com>
cc: Claudio Freire <klaussfreire@gmail.com>,
	Horst Dehmer <horst.dehmer@gmail.com>,
	postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: Insert performance for large transaction with multiple COPY FROM
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Comments: In-reply-to Jeff Janes <jeff.janes@gmail.com>
	message dated "Sat, 12 Jan 2013 13:23:33 -0800"
Date: Sat, 12 Jan 2013 17:26:51 -0500
Message-ID: <24687.1358029611@sss.pgh.pa.us>
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Jeff Janes <jeff.janes@gmail.com> writes:
> Will PG allow you to add a FK constraint where there is no usable
> index on the referenced side?

It will not, because the referenced side must have a unique constraint,
ie an index.

The standard performance gotcha here is not having an index on the
referencing side.  But that only hurts when doing UPDATEs/DELETEs of
referenced-side keys, which as far as I gathered was not the OP's
scenario.

			regards, tom lane


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