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

From: "Gokulakannan Somasundaram" <gokul007(at)gmail(dot)com>
To: "pgsql-hackers list" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Proposal for Null Bitmap Optimization(for Trailing NULLs)
Date: 2007-12-17 08:02:54
Message-ID: 9362e74e0712170002h25c5249ev43831f80e1d475af@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
We can also implement the same for index tuples.....


On Dec 17, 2007 1:10 PM, Gokulakannan Somasundaram <gokul007(at)gmail(dot)com>
wrote:

> Hi,
>     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
>
> a) By modifying the functions, heap_form_tuple and heap_fill_tuple, we can
> check whether all the nulls are trailing nulls. If all the nulls are
> trailing nulls, then we will not set the has_null flag and we will not have
> the null bitmap with the tuple.
>
> b) While selecting the tuple, we will check whether the tuple offset
> equals / exceeds the length of the tuple and then mark the remaining
> attributes of the tuple as null. To be exact, we need to modify the
> slot_deform_tuple in order to achieve the same.
>
> This may not give huge performance benefits, but as you may know, it will
> help is reducing the disk footprint.
>
>
> Expecting your comments..
>
> --
> Thanks,
> Gokul.
> CertoSQL Project,
> Allied Solution Group.
> (www.alliedgroups.com)




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

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