From: | Josh Berkus <josh(at)agliodbs(dot)com> |
---|---|
To: | Kevin Grittner <kgrittn(at)ymail(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com> |
Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Craig Ringer <craig(at)2ndquadrant(dot)com> |
Subject: | Re: INSERT ... ON CONFLICT {UPDATE | IGNORE} |
Date: | 2014-09-30 18:57:48 |
Message-ID: | 542AFD2C.3050005@agliodbs.com |
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Lists: | pgsql-hackers |
On 09/30/2014 07:15 AM, Kevin Grittner wrote:
> There are certainly other ways to do it, although they require more
> work. As far as UPSERT goes, I agree that we should require such
> an index, at least for the initial implementation and into the
> foreseeable future. What I'm saying is that if we implement it
> using the standard MERGE syntax, then if the features of MERGE are
> extended it will continue to work even in the absence of such an
> index. The index becomes a way of optimizing access rather than
> defining what access is allowed.
>
> At the risk of pushing people away from this POV, I'll point out
> that this is somewhat similar to what we do for unlogged bulk loads
> -- if all the conditions for doing it the fast way are present, we
> do it the fast way; otherwise it still works, but slower.
Except that switching between fast/slow bulk loads affects *only* the
speed of loading, not the locking rules. Having a statement silently
take a full table lock when we were expecting it to be concurrent
(because, for example, the index got rebuilt and someone forgot the
UNIQUE) violates POLA from my perspective.
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
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