On 02/07/2017 03:14 PM, Daniele Varrazzo wrote:
In psycopg '{}'::unknown is treated specially as an empty array and converted into an empty list, which allows empty lists to be passed to the server as arrays and returned back to python. Without the special case, empty lists behave differently from non-empty ones. It seems this behaviour cannot be maintained on PG 10 and instead users need to specify some form of cast for their placeholder. Previously this would have worked "as expected" and the 4th argument would have been an empty list:cur.execute("SELECT %s, %s, %s, %s", (['x'], [42], [date(2017,1,1)], [])); cur.fetchone() (['x'], [42], [datetime.date(2017, 1, 1)], '{}')
As Tom wrote this is the result of an intentional change, but no matter if that change is a good thing or not the above behavior sounds rather fragile. To me it does not seem safe to by default just assume that '{}' means the empty array, it might also have been intended to be the Python string "{}", the empty JSON object, or entirely something different.
Andreas -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
