When using currval() to find the current value of all sequences, it chokes on those that aren't initialised. This is expected and documented as behaving in this manner. However, I think it would be useful to also support retrieving the current value of a sequence, regardless of whether it's been used. As this wouldn't be to get a sequence value for the current session, but all sessions, this would ideally get the real current value.
The use-case I have in mind is for finding out how close to the 32-bit integer limit sequences have reached. At the moment, this isn't possible without creating a custom function to go fetch the last_value from the specified sequence.
So would it be desirable to have a function which accepts a sequence regclass as a parameter, and returns the last_value from the sequence?
Effectively, the same result as what this provides:
CREATE FUNCTION lastval(tablename regclass) RETURNS bigint AS $$ DECLARE last_value bigint; BEGIN EXECUTE format('SELECT last_value FROM %I ', tablename) INTO last_value USING tablename; RETURN last_value; END $$ LANGUAGE plpgsql;