def is_explainable(query):

    # See <http://www.postgresql.org/docs/8.3/static/sql-explain.html#AEN57749>

    return re.match('^(?:SELECT|INSERT|UPDATE|DELETE|VALUES|EXECUTE|DECLARE)\b',

        query)

def explain(db, query):

    return strings.join_lines(values(run_query(db, 'EXPLAIN '+query,

        recover=True, cacheable=True, log_level=3)))

        # not a higher log_level because it's useful to see what query is being

        # run before it's executed, which EXPLAIN effectively provides