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Re: R: space taken by a row & compressed data

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Leonardo Francalanci <lfrancalanci(at)simtel(dot)ie>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: R: space taken by a row & compressed data
Date: 2004-08-26 16:08:43
Message-ID: 200408261608.i7QG8hL07139@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-general
Leonardo Francalanci wrote:
> > We have an FAQ item about this.
> 
> Damn! I didn't see that one! Sorry...
> 
> > Long data values are automatically compressed.
> 
> The reason I'm asking is:
> we have a system that stores 200,000,000 rows per month
> (other tables store 10,000,000 rows per month)
> Every row has 400 columns of integers + 2 columns (date+integer) as index.
> 
> Our system compresses rows before writing them to a binary file on disk.
> Data don't usually need to be updated/removed.
> We usually access all columns of a row (hence compression on a per-row basis
> makes sense).
> 
> Is there any way to compress data on a per-row basis? Maybe with
> a User-Defined type?

Ah, we only compress long row values, which integers would not be.  I
don't see any way to compress an entire row even with a user-defined
type unless you put multiple values into a single column and compress
those as a single value.  In fact, if you used an array or some special
data type it would become a long value and would be automatically
compressed.

However, as integers, there would have to be a lot of duplicate values
before compression would be a win.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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