Re: UNDO and in-place update

On Wed, Jan 4, 2017 at 4:35 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> In this new system, I
> think we can't remove undo entries of heap page till we clear
> corresponding index entries. I think we need to somehow collect the
> old values from undo corresponding to index and then scan the index
> remove the index entry and after that corresponding undo entry can be
> removed.

Do we really need to keep undo for heap until index entry is not
removed? IIUC, we anyway need to revalidate the index key with heap
tuple. What I am trying the say is that if we no longer needed UNDO
for the heap page (e.g because of rollback) then we can apply the UNDO
and remove it. I agree that there will be multiple index entries will
be pointing to this tuple, but only one of them can pass the key
revalidation with the heap. isn't it?

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com