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Re: LRU and full table scans

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Mike Mascari <mascarm(at)mascari(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: LRU and full table scans
Date: 2002-02-28 03:42:21
Message-ID: 200202280342.g1S3gLj19261@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Mike Mascari wrote:
> On general a discussion has been taking place regarding cached query
> plans and how MySQL invented them. Of course, this is totally false. I
> remembered a nice paragraph in the Oracle docs as to the process by
> which Oracle uses shared SQL areas to share the execution plan of
> identical statements, flushing the area whenever a dependent object was
> modified. In searching for the reference, however, I stumbled an
> interesting fact. Unlike normal queries where blocks are added to the
> MRU end of an LRU list, full table scans add the blocks to the LRU end
> of the LRU list. I was wondering, in the light of the discussion of
> using LRU-K, if PostgreSQL does, or if anyone has tried, this technique?

Yes, someone from India has a project to test LRU-K and MRU for large
table scans and report back the results.  He will implement whichever is
best.  He posted a week ago, see "Implementation Proposal For Add Free
Behind Capability For Large Sequential Scan", Amit Kumar Khare
<skamit2000(at)yahoo(dot)com>.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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