Add support for bitwise XOR to expressions.

[Hannes Ljungberg]

It would be nice to get support for performing bitwise XOR on expressions. I'm aware of #29865 but from my understanding this ticket is about logical XOR and not bitwise XOR. Let me know if that ticket should be used instead.

My proposal is to implement this just like the other bitwise-functions, i.e Combinable.bitxor(other).

The connector defined by Combinable could be # , this is what PostgresSQL use, see ​https://www.postgresql.org/docs/current/functions-bitstring.html. I guess a more natural choice would’ve been ^ but this connector is already in use by Combinable.POW:
​https://github.com/django/django/blob/291539a85c8461456ab728fe6820a86de54294b6/django/db/models/expressions.py#L42

Bitwise XOR is supported by all backends except sqlite. It could be implemented on sqlite as something like ((%(lhs)s | %(rhs)s) - (%(lhs)s & %(rhs)s)) but the way CombinedExpression.as_sql is implemented makes it a bit tricky to repeat the right-hand side binding:
((“left_hand_side_expr" | %s) - ("left_hand_side_expr" & %s)) % (rhs,) .

Maybe it could be OK to set django.db.backends.sqlite3.features.DatabaseFeatures.supports_bitwise_xor = False

I have a proof-of-concept ready if this would be accepted.

[Mariusz Felisiak]

Replying to Hannes Ljungberg:

Bitwise XOR is supported by all backends except sqlite. It could be implemented on sqlite as something like ((%(lhs)s | %(rhs)s) - (%(lhs)s & %(rhs)s)) but the way CombinedExpression.as_sql is implemented makes it a bit tricky to repeat the right-hand side binding:
((“left_hand_side_expr" | %s) - ("left_hand_side_expr" & %s)) % (rhs,) .

You can override a bitxor operator (e.g. #) in DatabaseOperations.combine_expression() for each backend.

[Hannes Ljungberg]

PR: ​https://github.com/django/django/pull/12617

[Mariusz Felisiak <felisiak.mariusz@…>]

In f3da09df:

Fixed #31396 -- Added binary XOR operator to F expressions.