Tom Lane wrote:
The proposed behavior of txid_current_snapshot would defeat any possibility
of such an optimization, because we'd have to keep around the xact's oldest
snapshot on the off chance that txid_current_snapshot would be called later
in the xact.
I think txid_current_snapshot should read ActiveSnapshot. If the user wants
to get a beginning-of-xact rather than beginning-of-statement snapshot from
it, he should be required to call it in a serializable transaction.
Hm... does txid require that the snapshot it uses a valid in the sense that
its xmin follows OldestXmin? If not, we could keep the snapshot around for txid,
but still update our published xmin - which seems to be the main reason we care
about getting rid of old snapshots at all.
greetings, Florian Pflug
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