Re: cast bytea to double precision[]

From: Mathieu Dubois <mathieu(dot)dubois(at)limsi(dot)fr>
To: pgsql-novice(at)postgresql(dot)org
Subject: Re: cast bytea to double precision[]
Date: 2011-07-27 09:06:43
Message-ID: 4E2FD523.6010400@limsi.fr
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-novice

Hello,

This morning I conducted a simple test: I generated 10 000 samples of
100-dimensional data (uniformly distributed in [-10 000; 10 000]) and
inserted them into 2 newly created bases with only 1 table each. In one
case the table has a bytea column (table OID 2102835) on the other a
double precision[] (table OID 2102836). I generated scripts to insert
the data in the 2 formats.

After insertion, 'du -h' gives:
22M ./2102835
15M ./2102836

So the double precision[] is really smaller.

I guess that in my case (altering column) there may be some kind of
cache or maybe the toast table... It's really puzzling.

Mathieu
On 07/26/2011 09:19 PM, Merlin Moncure wrote:
> On Tue, Jul 26, 2011 at 2:02 PM, Mathieu Dubois<mathieu(dot)dubois(at)limsi(dot)fr> wrote:
>> Are you sure that the length of each element is stored?
> no, I was wrong (I just checked the code) -- see CopyArrayEls. Null
> indicator is stored in a bitmap. hm.
>
> merlin
>

In response to

Browse pgsql-novice by date

  From Date Subject
Next Message Soviet 2011-07-29 17:57:57 PostgreSQL on Amazon EC2/EBS
Previous Message David Alexander Krois 2011-07-27 08:53:12 Orphaned files in the subdirectory of the database