Performance Improvement for Unique Indexes

Hi,<br />   While i was studying the unique index checks very closely, i realized that what we need is to find out
whetherthe tuple is deleted / not. So say a tuple is deleted by a transaction, but it is not dead( because of some long
runningtransaction ), still we can mark a hint bit as deleted and it will help the subsequent transactions doing the
uniquechecks. As a matter of fact, it will help the deferred_unique cases, since it will anyway check the tuples twice,
ifthere is a duplicate.<br />    So we have one bit left in the Index Tuple that can be used as hint bit. If we are
readyto break the disk compatibility, then we can store the size as a multiple of 8, and we will get three bits free.
Anycomments?<br /><br />Thanks,<br />Gokul.<br />