Proposal for Null Bitmap Optimization(for Trailing NULLs)

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)