Re: sorting table columns

Excerpts from Simon Riggs's message of mié dic 21 09:44:04 -0300 2011:

> Sounds great.
>
> While you're doing this, I'd like to think about future requirements,
> to see if that changes anything.
>
> Having a unique logical column id is a great thing because it allows
> the physical storage to differ. This is the first part to allowing
> these features...

Great ideas.  This one I'm not sure about at all:

> * "very large number of columns" for statistical data sets where we
> automatically vertically partition the heap when faced with large
> numbers of column definitions
>
> So when you store the physical representation please also store a
> storage method, that currently has just one method SM_HEAP and a
> relfilenode.

Well, for the patch I'm working on right now, I'm just going to store an
ID as "physical representation", which will mean the sort order used for
the on-disk representation of our current heap storage; the idea here is
to allow columns to be sorted internally by the system so that alignment
padding is reduced; nothing more.  Of course, we can work on more
complex representations later that allow different storage strategies,
such as the ones you propose.

--
Álvaro Herrera <alvherre@commandprompt.com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support