Re: How to extract a value from a record using attnum or attname?

Excerpts from Kevin Grittner's message of mar feb 22 20:29:26 -0300 2011:
> Andrew Dunstan <andrew@dunslane.net> wrote:
>  
> > Have you performance tested it? Scanning pg_index for index
> > columns for each row strikes me as likely to be unpleasant.
>  
> I haven't, yet.  I had rather assumed that the index info for a
> relation would have a high probability of being cached during
> execution of an AFTER trigger for that relation, so I think we're
> talking RAM access here.  It didn't seem sane to try to create an
> HTAB for this and worry about invalidation of it, etc.  If there's a
> faster way to get to the info without going to such extremes, I'd be
> happy to hear them.  (At least I avoided building and parsing a
> query to get at it.)

I think it'd be better to use RelationGetIndexList (which gets the index
list from relcache) and fetch the index tuples from syscache; see
relationHasPrimaryKey for sample code.

-- 
Álvaro Herrera <alvherre@commandprompt.com>
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