From: Eric Comeau <ecomeau@signiant.com>
Subject: How to get FK to use new index without restarting the database
Date: Thu, 16 Dec 2010 07:12:03 -0500
Organization: Hub.Org Networking Services
Lines: 25
Message-ID: <iecvmj$1j93$1@news.hub.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US;
	rv:1.9.2.13) Gecko/20101208 Lightning/1.0b2 Thunderbird/3.1.7
To: pgsql-performance@postgresql.org


Is there a way force the db to re-evaluate its execution plan for a FK 
without bouncing the DB?

  PostgreSQL 8.1.17

In our latest release our developers have implemented some new foreign 
keys but forgot to create indexes on these keys.

The problem surfaced at one of our client installs where a maintenance 
DELETE query was running for over 24 hrs. We have since then identified 
the missing indexes and have sent the client a script to create them, 
but in our testing we could not been able to get postgres to use the new 
index for the FK cascade delete without bouncing the database.

Here is an example of an added fk but missing index....

ALTER TABLE scheduled_job_arg ADD CONSTRAINT sjr_scheduled_job_id_fk
   FOREIGN KEY (scheduled_job_id) REFERENCES scheduled_job (id)
      ON UPDATE CASCADE ON DELETE CASCADE;

Thanks in Advance,
Eric