Re: Performance Improvement for Unique Indexes

On Wed, Mar 24, 2010 at 7:17 AM, Gokulakannan Somasundaram
<gokul007@gmail.com> wrote:
>    While i was studying the unique index checks very closely, i realized
> that what we need is to find out whether the tuple is deleted / not. So say
> a tuple is deleted by a transaction, but it is not dead( because of some
> long running transaction ), still we can mark a hint bit as deleted and it
> will help the subsequent transactions doing the unique checks. As a matter
> of fact, it will help the deferred_unique cases, since it will anyway check
> the tuples twice, if there is a duplicate.
>    So we have one bit left in the Index Tuple that can be used as hint bit.
> If we are ready to break the disk compatibility, then we can store the size
> as a multiple of 8, and we will get three bits free. Any comments?

I don't think this works.  The postulated long-running transaction
would also see the hint bit...

...Robert