Amit Kapila <amit.kapil...@gmail.com>:
> What if the new insert happens in a page prior to the current page? I > mean that the scan won't encounter the page where Insert happens. Hmm.... Yes - if the TID lands to the page left of the current position, we’ll miss it as well. A lock‑based solution (version in the v10) would require keeping all pages with the same key under a read lock, which feels too expensive. > BTW, do we know the reason behind using SnapshotDirty in the first > place? I don't see any comments in the nearby code unless I am missing > something. I think this is simply an attempt to lock the newest version of the logical tuple, including INSERT cases. For an existing tuple, the same can be achieved using MVCC snapshot + retry. However, in the case of a not-yet-committed INSERT, a different type of snapshot is required. But I'm not sure if it provides any advantages.
