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Re: User-facing aspects of serializable transactions

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Albe Laurenz" <laurenz(dot)albe(at)wien(dot)gv(dot)at>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: User-facing aspects of serializable transactions
Date: 2009-05-28 14:47:47
Message-ID: 4A1E5DC3.EE98.0025.1@wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-hackers
"Albe Laurenz" <laurenz(dot)albe(at)wien(dot)gv(dot)at> wrote:
 
> Every WHERE-clause in a SELECT will add one or more checks for each
> concurrent writer.
 
That has not been the case in any implementation of predicate locks
I've used so far.  It seems that any technique with those performance
characteristics would be one to avoid.
 
> From the user perspective, will an implementation of the paper's
> approach as an intermediate step provide a useful and understandable
> isolation level?
 
Well, to be clear, the paper states that predicate locking is a
requirement, but we've had some ideas about how we might make progress
without a full implemenation of that; so I guess your question should
be taken to mean "in the absence of full predicate locking support".
 
Possibly.  It would reduce the frequency of anomalies for those not
doing explicit locking, and Robert Haas has said that it might allow
him to drop some existing explicit locking.
 
-Kevin

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