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Storage space usage
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* Storage space usage
@ 2008-02-01 08:44  Gangadharan S.A. <gangadharan@gmail.com>
  0 siblings, 1 reply; 2+ messages in thread

From: Gangadharan S.A. @ 2008-02-01 08:44 UTC (permalink / raw)
  To: pgsql-performance

Hi,
I have 2 questions regarding the storage optimization done by Postgres:
1) Is a NULL value optimized for storage. If I have a timestamp (or some
such) field that I set to default NULL, will it still use up the full space
for the data type.
2) Similarly, if I have a text array, is an empty array optimized for
storage?
Thanks,
Gangadharan

^ permalink  raw  reply  [nested|flat] 2+ messages in thread

* Re: Storage space usage
@ 2008-02-02 06:37  Decibel! <decibel@decibel.org>
  parent: Gangadharan S.A. <gangadharan@gmail.com>
  0 siblings, 0 replies; 2+ messages in thread

From: Decibel! @ 2008-02-02 06:37 UTC (permalink / raw)
  To: Gangadharan S.A. <gangadharan@gmail.com>; +Cc: pgsql-performance

On Fri, Feb 01, 2008 at 02:14:18PM +0530, Gangadharan S.A. wrote:
> Hi,
> I have 2 questions regarding the storage optimization done by Postgres:
> 1) Is a NULL value optimized for storage. If I have a timestamp (or some
> such) field that I set to default NULL, will it still use up the full space
> for the data type.

Null values are indicated via a NULL bitmap. A null field is not stored,
it is just indicated in the bitmap.

> 2) Similarly, if I have a text array, is an empty array optimized for
> storage?

Arrays are stored as varlenas. I'm pretty sure than an empty array is
considered to be NULL; as such the comments above would apply.
-- 
Decibel!, aka Jim C. Nasby, Database Architect  decibel@decibel.org 
Give your computer some brain candy! www.distributed.net Team #1828

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