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Re: Read Committed isolation

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Oliver Crow <ocrow(at)simplexity(dot)net>
Cc: pgsql-docs(at)postgresql(dot)org, tgl(at)sss(dot)pgh(dot)pa(dot)us
Subject: Re: Read Committed isolation
Date: 2003-03-18 00:57:12
Message-ID: 200303180057.h2I0vCj04681@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-docs
I guess the big question is whether we want to be teaching isolation
level concepts in our manual.  It is a standard database concept.

---------------------------------------------------------------------------

Oliver Crow wrote:
> 
> Hi all,
> 
> It seems to me that the PostgreSQL user's manual could be clearer on the
> consequences of using the Read Committed isolation level.
> 
> It says "The partial transaction isolation provided by Read Committed
> mode is adequate for many applications" ... "However, for applications
> that do complex queries and updates, it may be necessary to guarantee a
> more rigorously consistent view of the database".
> 
> It does not say what types of transactions will cause problems in Read
> Committed mode, or what the consequences of those problems might be.
> This is a point on which the manual ought to be explicit ... the potential
> for intermittent creation of database inconsistencies is serious. For
> example, if information from a select is passed via the application to an
> update, the transaction could reintroduce stale information.
> 
> This message provides some good explanation with examples:
> http://archives.postgresql.org/pgsql-hackers/2002-04/msg00150.php
> 
> 
> It also speaks clearly about when a serializable transaction may need to
> be repeated, and the possible trade off between using serializable or
> SELECT FOR UPDATE.  Could an edited version of that message be included in
> the manual?  (I'd be willing to assist with editing)
> 
> 
> Thanks, Oliver
> 
> 
> 
> 
> 
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-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
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