Re: Proposal for Null Bitmap Optimization(for TrailingNULLs) - Mailing list pgsql-hackers

From Gokulakannan Somasundaram
Subject Re: Proposal for Null Bitmap Optimization(for TrailingNULLs)
Date
Msg-id 9362e74e0712181117ufe54b33y6ffcbcb28cc6eecc@mail.gmail.com
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In response to Re: Proposal for Null Bitmap Optimization(for TrailingNULLs)  ("Gokulakannan Somasundaram" <gokul007@gmail.com>)
Responses Re: Proposal for Null Bitmap Optimization(for TrailingNULLs)  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
Hi,
   I have currently completed the following
a) If there are only trailing nulls in the heap, no null-bitmap gets stored
b) If there are trailing nulls in addition to nulls inbetween values in the heap, then the trailing nulls are not added to the null-bitmap. I wouldn't have done it, but it came almost free of cost
c) If there are only trailing nulls in the index, no null-bitmap gets stored

The index part gave some issues and i hope i have fixed it. i am still testing it(feeling sleepy :)). So i will post the patch, as soon as i complete testing.

Thanks,
Gokul.

On Dec 18, 2007 12:05 AM, Gokulakannan Somasundaram <gokul007@gmail.com> wrote:
Hi,
   I made the fix and tested it today. It involved some 10-15 lines of code change. I will mail it tomorrow. Feel free to give suggestions on making the fix more maintainable.
   I have followed Gregory's advice in the fix -  Instead of changing the slot_deform_tuple, i have reduced the number of attributes field of the HeapTupleHeader(during insertion), so that the trailing nulls are treated the same as newly added columns. Thanks Gregory.
   Regarding arrangement of the columns, my take is to leave it to the user on the arrangement of the columns. May be we can put some kind of tuning hint somewhere in our document on the suggestions. I have made the above statement, without thinking about other advantages, if any. 



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



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

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