| From: | mark(at)mark(dot)mielke(dot)cc |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Csaba Nagy <nagy(at)ecircle-ag(dot)com>, Martijn van Oosterhout <kleptog(at)svana(dot)org>, Zeugswetter Andreas DCP SD <ZeugswetterA(at)spardat(dot)at>, Dann Corbit <DCorbit(at)connx(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Rick Gigger <rick(at)alpinenetworking(dot)com>, Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>, "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>, josh(at)agliodbs(dot)com, pgsql-hackers(at)postgresql(dot)org, Jaime Casanova <systemguards(at)gmail(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net> |
| Subject: | Re: MERGE vs REPLACE |
| Date: | 2005-11-17 17:31:17 |
| Message-ID: | 20051117173117.GA27563@mark.mielke.cc |
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| Lists: | pgsql-hackers |
On Thu, Nov 17, 2005 at 10:15:30AM -0500, Stephen Frost wrote:
> REPLACE/INSERT ON DUPLICATE UPDATE appears to essentially be a
> transaction which is supposed to not fail but instead do locking to
> ensure that it doesn't fail. This requires predicate locking to be
> efficient because you want to tell the concurrent transaction "if you
> have the same key as me, just wait a second and you can do an update
> 'cause I'm going to create the key if it doesn't exist before I'm done".
Is the requirement for predicate locking, over and above a unique
constraint on an index that involves the record key, to deal with
the scenario of two inserts executing at the same time, both before
commit?
Cheers,
mark
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