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-- In PostgreSQL, the most straightforward query would be to run:
-- SELECT currval(pg_get_serial_sequence('Changes', 'seq'))".
-- Unfortunately, this raises the error message "currval of sequence
-- "changes_seq_seq" is not yet defined in this session" if no change
-- has been inserted before the SELECT. We thus track the sequence
-- index with a trigger.
-- http://www.neilconway.org/docs/sequences/
INSERT INTO GlobalIntegers
SELECT 6, CAST(COALESCE(MAX(seq), 0) AS BIGINT) FROM Changes;
CREATE FUNCTION InsertedChangeFunc()
RETURNS TRIGGER AS $body$
BEGIN
UPDATE GlobalIntegers SET value = new.seq WHERE key = 6;
RETURN NULL;
END;
$body$ LANGUAGE plpgsql;
CREATE TRIGGER InsertedChange
AFTER INSERT ON Changes
FOR EACH ROW
EXECUTE PROCEDURE InsertedChangeFunc();
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