On Tue, 2022-03-08 at 06:29 -0700, Michael Lewis wrote: > "The DEFERRABLE transaction property has no effect unless the transaction is > also > SERIALIZABLE and READ ONLY. When all three of these properties are selected > for a transaction, > the transaction may block when first acquiring its snapshot, after which it > is able to run > without the normal overhead of a SERIALIZABLE transaction and without any > risk of contributing > to or being canceled by a serialization failure. This mode is well suited for > long-running reports or backups." > > > Could anyone expound on the above? What are the real life differences between > the two commands below? Would this be applicable at all to sessions on a > physical replica? > > SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL SERIALIZABLE READ > ONLY DEFERRABLE; > > SET SESSION CHARACTERISTICS AS TRANSACTION READ ONLY;
A transaction started with the first statement will not take any SI locks, nor will it ever receive a serialization error. Yours, Laurenz Albe -- Cybertec | https://www.cybertec-postgresql.com
