How to query last_value of a sequence using late-binding-CodePudding

Is it possible to obtain the last value from a sequence of which name is stored in a variable?

seq_name := 'myschema.mysequence';
SELECT last_value FROM ${seq_name};

CodePudding user response：

If the sequence has already been used in the session, you can simply user the currval function:

DO
$$DECLARE
   var text := 'seq';
BEGIN
   RAISE NOTICE 'The current value is %', currval(var);
END;$$;

NOTICE:  The next value is 1

Otherwise, you need dynamic SQL:

DO
$$DECLARE
   var text := 'seq';
   value bigint;
BEGIN
   EXECUTE format('SELECT last_value FROM %s', var) INTO value;
   RAISE NOTICE 'The current value is %', value;
END;$$;

NOTICE:  The current value is 1