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Re: Proposed patch to change TOAST compression strategy

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: <pgsql-patches(at)postgreSQL(dot)org>, "Jan Wieck" <JanWieck(at)Yahoo(dot)com>
Subject: Re: Proposed patch to change TOAST compression strategy
Date: 2008-02-18 10:33:38
Message-ID: 87ir0mo8ot.fsf@oxford.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-patches
"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> * Adds an early-failure path to the compressor as suggested by Jan:
> if it's been unable to find even one compressible substring in the
> first 1KB (parameterizable), assume we're looking at incompressible
> input and give up.  (There are various ways this could be done, but
> this way seems to add the least overhead to the compressor's inner
> loop.)

I'm not sure how to test the rest of it, but this bit seems testable. I fear
this may be too conservative. Even nigh incompressible data will find a few
backreferences.

I'll try some tests and see.

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com
  Ask me about EnterpriseDB's On-Demand Production Tuning

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