Tiago Wright <tiagowright@gmail.com> writes:
> Yes, thanks Tom. This is precisely what I was missing. I searched the
> archives for the reason why this is so, but I found only one message
> mentioning the MVCC mechanism. Can you point me in the right
> direction? I would like to understand the issue.
Short answer: MVCC tuple visibility status isn't (and can't be) stored
in the index. So the backend has to visit the actual tuple to see if
it is visible to the transaction that is currently running.
> IMHO, a change in this area could deliver great performance improvements.
Hard to say how it would work, but come up with a good design and
quality patch and it'll probably go in. :)
-Doug
--
Let us cross over the river, and rest under the shade of the trees. --T. J. Jackson, 1863