perf: use `b"'"[0]` as const value to represent `ord("'")`

The value is expanded at compile time::

    >>> dis.dis('b"\'"[0]')
      1           0 LOAD_CONST               0 (39)
                  2 RETURN_VALUE

diff --git a/psycopg/psycopg/sql.py b/psycopg/psycopg/sql.py
index eb5be8aefc9564d85b95a701be439001d5c3d434..4e0d0d3dece6fe6f1e3cb8fa066dd1bdb0b08df4 100644 (file)
--- a/psycopg/psycopg/sql.py
+++ b/psycopg/psycopg/sql.py
@@ -395,7 +395,7 @@ class Literal(Composable):
         rv = dumper.quote(self._obj)
         # If the result is quoted and the oid not unknown,
         # add an explicit type cast.
-        if rv[-1] == 39 and dumper.oid:
+        if rv[-1] == b"'"[0] and dumper.oid:
             ti = tx.adapters.types.get(dumper.oid)
             if ti:
                 # TODO: ugly encoding just to be decoded by as_string()