Re: reducing NUMERIC size for 9.1

Richard Huxton <dev@archonet.com>

From: Richard Huxton <dev@archonet.com>
To: Brendan Jurd <direvus@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2010-07-16T12:51:23Z
Lists: pgsql-hackers
On 16/07/10 13:44, Brendan Jurd wrote:
>
> pg_column_size() did return the results I was expecting.
> pg_column_size(0::numeric) is 8 bytes on 8.4 and it's 6 bytes on HEAD
> with your patch.

> At this scale we should be seeing around 2 million bytes saved, but
> instead the tables are identical.  Is there some kind of disconnect in
> how the new short numeric is making it to the disk, or perhaps another
> effect interfering with my test?

You've probably got rows being aligned to a 4-byte boundary. You're 
probably not going to see any change unless you have a couple of 1-byte 
columns that get placed after the numeric. If you went from 10 bytes 
down to 8, that should be visible.

-- 
   Richard Huxton
   Archonet Ltd