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Re: pgsql: Create a GUC parametertemp_tablespacesthat allows selection of

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: <pgsql-committers(at)postgresql(dot)org>,<pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pgsql: Create a GUC parametertemp_tablespacesthat allows selection of
Date: 2007-06-04 19:12:44
Message-ID: 1180984364.2870.82.camel@silverbirch.site (view raw or flat)
Thread:
Lists: pgsql-committerspgsql-hackers
On Mon, 2007-06-04 at 14:41 -0400, Tom Lane wrote:
> "Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
> > One of the main reasons for the implementation was to allow larger
> > queries to work faster by utilising multiple temp tablespaces for the
> > same query.
> 
> > The original ideal implementation was to use round-robin/cyclic
> > selection, which allows much better usage in the above case.
> 
> Really?  What if multiple backends are all hitting the same tablespaces
> in the same order?  A random selection seems much less likely to risk
> having any self-synchronizing behavior.

I'd like a single backend to never reuse a temp tablespace that is
actively being used so that large queries won't randomly conflict with
themselves. That's pretty certain to draw complaints, IMHO.

We can do this two ways
- cycle thru temp tablespaces, as originally suggested (not by me...)
- pick a random tablespace **other than ones already in active use**

-- 
  Simon Riggs             
  EnterpriseDB   http://www.enterprisedb.com



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