Re: Make HeapTupleSatisfiesMVCC more concurrent

On Wed, Aug 19, 2015 at 2:53 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> I think one case where the patch can impact is for aborted transactions.
> In TransactionIdIsInProgress(), we check for aborted transactions before
> consulting pg_subtrans whereas with patch it will consult pg_subtrans
> without aborted transaction check.  Now it could be better to first check
> pg_subtrans if we found that the corresponding top transaction is
> in-progress as that will save extra pg_clog lookup, but I just mentioned
> because that is one difference that I could see with this patch.
>
> Another minor point is, I think we should modify function level comment
> for XidInMVCCSnapshot() where it says that this applies to known-
> committed XIDs which will no longer be true after this patch.

But only if the snapshot has overflowed, right?  That should affect
only a small minority of cases.

-- 
Robert Haas
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