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Re: contrib idea

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>, Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: contrib idea
Date: 2002-01-03 06:25:52
Message-ID: 200201030625.g036PqR16995@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> >> If you have a foreign key on a column, then whenever the primary key is
> >> modified, the following checks may occur:
> >> 
> >> * Check to see if the child row exists (no action)
> >> * Delete the child row (cascade delete)
> >> * Update the child row (cascade update)
> >> 
> >> All of which will benefit from an index...
> 
> > OK, then perhaps we should be creating an index automatically?  Folks?
> 
> We should not *force* people to have an index.  If the master table very
> seldom changes, then an index on the referencing table will be a net
> loss (at least as far as the foreign-key ops go).  You'll pay for it on
> every referencing-table update, and use it only seldom.
> 
> Possibly there should be an entry in the "performance tips" chapter
> recommending that people consider adding an index on the referencing
> column if they are concerned about the speed of updates to the
> referenced table.  But I dislike software that considers itself smarter
> than the DBA.

OK, I have added the following to the create_lang.sgml manual page.  I
couldn't find a good place to put this in the performance page.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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