From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
---|---|
To: | Peter Geoghegan <pg(at)heroku(dot)com> |
Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Anssi Kääriäinen <anssi(dot)kaariainen(at)thl(dot)fi>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Kevin Grittner <kgrittn(at)ymail(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: INSERT ... ON CONFLICT {UPDATE | IGNORE} |
Date: | 2014-12-20 10:16:47 |
Message-ID: | 20141220101646.GA7606@svana.org |
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Lists: | pgsql-hackers |
On Fri, Dec 19, 2014 at 05:32:43PM -0800, Peter Geoghegan wrote:
> > Most people would list the columns, but if there is a really bizarre
> > constraint, with non-default opclasses, or an exclusion constraint, it's
> > probably been given a name that you could use.
>
> What I find curious about the opclass thing is: when do you ever have
> an opclass that has a different idea of equality than the default
> opclass for the type? In other words, when is B-Tree strategy number 3
> not actually '=' in practice, for *any* B-Tree opclass? Certainly, it
> doesn't appear to be the case that it isn't so with any shipped
> opclasses - the shipped non-default B-Tree opclasses only serve to
> provide alternative notions of sort order, and never "equals".
Well, in theory you could build a case insensetive index on a text
column. You could argue that the column should have been defined as
citext in the first place, but it might not for various reasons.
Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> He who writes carelessly confesses thereby at the very outset that he does
> not attach much importance to his own thoughts.
-- Arthur Schopenhauer
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