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

We can also implement the same for index tuples.....<br /><br /><br /><div class="gmail_quote">On Dec 17, 2007 1:10 PM,
GokulakannanSomasundaram <<a href="mailto:gokul007@gmail.com">gokul007@gmail.com</a>> wrote:<br /><blockquote
class="gmail_quote"style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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" /><font color="#888888"><br />--
<br/>Thanks,<br />Gokul. <br />CertoSQL Project,<br /> Allied Solution Group.<br />(<a
href="http://www.alliedgroups.com"target="_blank">www.alliedgroups.com</a>) </font></blockquote></div><br /><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>)