Thread

Re: When creating index, why pointing to old version of tuple

Tender Wang <tndrwang@gmail.com> — 2025-08-01T06:58:22Z

Chao Li <li.evan.chao@gmail.com> 于2025年8月1日周五 14:47写道：

> > If the index points to the newest version of the tuple, how do old
> transactions read the old version of the tuple using an index scan for old
> transactions?
>
> Say there is a long transaction x1, it is on-going.
>
> And transaction x2 started later than x1 started, and x2 created an index.
> Should x1 be visible to the new index?
>
> My understanding is, the old transaction x1 cannot use the new index to
> scan for the old version of the tuple. If you read my example, in the
> index, the key is the new age value (99), while the old age value is 4,
> thus using the old value will not hit the index entry.
>

Yeah, in your case, the index is non-visible for x1. Your saying is
correct.  But what if the table already has an index?
-- 
Thanks,
Tender Wang