Обсуждение: Question about MVCC caveats
At [1], the docs state that table rewrite ALTERs result in the relation appearing empty after the ALTER if another transaction had already taken a snapshot before the ALTER. A simple test with a repeatable read (or serializable) transaction confirms this... but is there any other situation where a snapshot would be taken?
On Thu, 2025-11-13 at 13:30 -0600, Jim Nasby wrote: > At [1], the docs state that table rewrite ALTERs result in the relation appearing > empty after the ALTER if another transaction had already taken a snapshot before > the ALTER. A simple test with a repeatable read (or serializable) transaction > confirms this... but is there any other situation where a snapshot would be taken? Snapshots are taken at the start of a statement (or, with REPEATABLE READ and SERIALIZABLE) at the beginning of the first statement in the transaction. What do you mean with an "other" situation? Yours, Laurenz Albe