From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Richard Huxton <dev(at)archonet(dot)com> |
Cc: | David Garamond <lists(at)zara(dot)6(dot)isreserved(dot)com>, pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: fixed-length row |
Date: | 2004-01-25 00:54:08 |
Message-ID: | 200401250054.i0P0s8n09515@candle.pha.pa.us |
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Lists: | pgsql-general |
Richard Huxton wrote:
> On Thursday 15 January 2004 14:17, David Garamond wrote:
> > The MySQL manual recommends that we create a "fixed-length row" if
> > possible, for speed (especially scanning speed). A fixed-length row is a
> > row which is comprised of only fixed-length fields. A fixed-length field
> > takes a fixed amount of bytes for storage (e.g. INT = 4 bytes, CHAR(M) =
> > M bytes, etc).
> >
> > Is there a similar recommendation in PostgreSQL? I notice that most data
> > types are stored in variable-length mode anyway (is cidr and inet data
> > types fixed-length?)
>
> Not really - there have been various discussions about timing differences
> between char() and varchar() and I don't recall one being noticably faster
> than the others.
>
> > Is there a command/query in psql which can show storage requirement for
> > each field? For example:
>
> No, but there's stuff in the archives, and I think something on techdocs too.
FAQ item 4.14 covers this, and reports CHAR() and VARCHAR() have the
same performance characteristics.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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