Re: Proposal for Null Bitmap Optimization(for Trailing NULLs)

On Dec 17, 2007 3:28 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:

> On Mon, 2007-12-17 at 13:10 +0530, Gokulakannan Somasundaram wrote:
>
> > Currently we check for the existence of NULL values in the tuple
> > and we set the has_null flag. If the has_null flag is present, the
> > tuple will be storing a null bitmap. What i propose is
>
> Will this work for ALTER TABLE when adding and dropping columns?

When we drop columns, it is not at all an issue. When we add columns, by
default they have null values. If we want to set default, postgres allows it
only for new inserts. Can you think of any specific instance.

>
>
> Another idea is to store the bitmap from the first nullable column.

This is a different idea. I like this. I will think about this also.

>
>
> Some of these ideas have been discussed before, so I would check the
> archives thoroughly. Most everything has if you look closely enough.

I have done a fair amount of search in the archives. But if you remember any
please notify me about it.

>
>
> --
> Simon Riggs
> 2ndQuadrant http://www.2ndQuadrant.com
>
>

--
Thanks,
Gokul.
CertoSQL Project,
Allied Solution Group.
(www.alliedgroups.com)