Comment 8 for bug 187047

Nice stuff. Three minor comments which we discussed:

[1]

We have to check the SQL precedence rules, as PostgreSQL seems
to have different rules than the one used in the branch.

[2]

    def compile_bitwise_xor_postgres(compile, expr, state):
        expr.oper = "#"

This changes the expression passed by the user, which may be unexpected.
It'd be nice to just return the compiled statement from this handler.

[3]

    BitwiseXor

BitwiseXOr is probably the most expected spelling, as we discussed live.

Thanks for the branch! +1!