Re: Stats for multi-column indexes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Richard Huxton <dev(at)archonet(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>, Jeff Davis <pgsql(at)j-davis(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Stats for multi-column indexes
Date: 2007-03-20 15:28:52
Message-ID: 14054.1174404532@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> It was also suggested that column pairs in FK relationship could be
> automatically enabled. So you don't need to specify those manually.

Actually, I think you don't particularly need stats for that in most
cases --- if the planner simply took note that the FK relationship
exists, it would know that each row of the FK side joins to exactly
one row of the PK side, which in typical cases is sufficient.

regards, tom lane

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