According to the documentation. now() should yield the timestamp of the current transaction, while statement_timestamp() should yield the timestamp of the current statement.
In case of Autocommit, both should be identical, in case of a running transaction, they should be different.
Funny enough, psql and executing the same statement from within an application yield different results. I tried a Tcl script and DBeaver.
Statement: SELECT now(), statement_timestamp();
psql: 2021-05-07 13:31:10.135851+02 | 2021-05-07 13:31:10.135851+02
DBeaver: 2021-05-07 13:31:00.633784+02|2021-05-07 13:31:00.633913+02
Tcl script: {now {2021-05-07 13:24:54.659837+02} statement_timestamp {2021-05-07 13:24:54.65985+02}}
So in psql now() and statement_timestamp() are identical when not in a transaction, while in the others the two values vary a little bit, roughly 100 microseconds.
How come the same statements aren't behaving identical. I'm using a current PostgreSQL server on a Linux machine.
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