Proposal for Null Bitmap Optimization(for Trailing NULLs) - Mailing list pgsql-hackers

From Gokulakannan Somasundaram
Subject Proposal for Null Bitmap Optimization(for Trailing NULLs)
Date
Msg-id 9362e74e0712162340j294c37e7q69d0c52b17acb614@mail.gmail.com
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Responses Re: Proposal for Null Bitmap Optimization(for Trailing NULLs)  ("Gokulakannan Somasundaram" <gokul007@gmail.com>)
Re: Proposal for Null Bitmap Optimization(for Trailing NULLs)  (Gregory Stark <stark@enterprisedb.com>)
Re: Proposal for Null Bitmap Optimization(for Trailing NULLs)  (Simon Riggs <simon@2ndquadrant.com>)
Re: Proposal for Null Bitmap Optimization(for Trailing NULLs)  (Bruce Momjian <bruce@momjian.us>)
List pgsql-hackers
Hi,<br />    Currently we check for the existence of NULL values in the tuple and we set the has_null flag. If the
has_nullflag is present, the tuple will be storing a null bitmap. What i propose is<br /><br />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
aretrailing nulls, then we will not set the has_null flag and we will not have the null bitmap with the tuple. <br
/><br/>b) While selecting the tuple, we will check whether the tuple offset equals / exceeds the length of the tuple
andthen mark the remaining attributes of the tuple as null. To be exact, we need to modify the slot_deform_tuple in
orderto achieve the same. <br /><br />This may not give huge performance benefits, but as you may know, it will help is
reducingthe disk footprint.<br /><br /><br />Expecting your comments..<br clear="all" /><br />-- <br />Thanks,<br
/>Gokul.<br/>CertoSQL Project,<br /> Allied Solution Group.<br />(<a
href="http://www.alliedgroups.com">www.alliedgroups.com</a>) 

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