PHP Postgres: Get Last Insert ID

Question

I found a couple of other questions on this topic. This one...

mysql_insert_id alternative for postgresql

...and the manual seem to indicate that you can call lastval() any time and it will work as expected. But this one...

Postgresql and PHP: is the currval a efficent way to retrieve the last row inserted id, in a multiuser application?

...seems to state that it has to be within a transaction. So my question is this: can I just wait as long as I like before querying for lastval() (without a transaction)? And is that reliable in the face of many concurrent connections?

Answer 1

INSERT, UPDATE and DELETE in PostgreSQL have a RETURNING clause which means you can do:

INSERT INTO ....
RETURNING id;

Then the query will return the value it inserted for id for each row inserted. Saves a roundtrip to the server.

Answer 2

Yes, the sequence functions provide multiuser-safe methods for obtaining successive sequence values from sequence objects.