Genericize setinputsizes and support pyodbc

Reworked the "setinputsizes()" set of dialect hooks to be correctly
extensible for any arbirary DBAPI, by allowing dialects individual hooks
that may invoke cursor.setinputsizes() in the appropriate style for that
DBAPI.   In particular this is intended to support pyodbc's style of usage
which is fundamentally different from that of cx_Oracle.  Added support
for pyodbc.

Fixes: #5649
Change-Id: I9f1794f8368bf3663a286932cfe3992dae244a10

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/sqlalchemy/connectors/pyodbc.py b/lib/sqlalchemy/connectors/pyodbc.py
index e1a7c99f4..780161304 100644
--- a/lib/sqlalchemy/connectors/pyodbc.py
+++ b/lib/sqlalchemy/connectors/pyodbc.py
@@ -24,6 +24,8 @@ class PyODBCConnector(Connector):
     supports_native_decimal = True
     default_paramstyle = "named"
 
+    use_setinputsizes = True
+
     # for non-DSN connections, this *may* be used to
     # hold the desired driver name
     pyodbc_driver_name = None
@@ -155,6 +157,21 @@ class PyODBCConnector(Connector):
                     version.append(n)
         return tuple(version)
 
+    def do_set_input_sizes(self, cursor, list_of_tuples, context):
+        # the rules for these types seems a little strange, as you can pass
+        # non-tuples as well as tuples, however it seems to assume "0"
+        # for the subsequent values if you don't pass a tuple which fails
+        # for types such as pyodbc.SQL_WLONGVARCHAR, which is the datatype
+        # that ticket #5649 is targeting.
+        cursor.setinputsizes(
+            [
+                (dbtype, None, None)
+                if not isinstance(dbtype, tuple)
+                else dbtype
+                for key, dbtype, sqltype in list_of_tuples
+            ]
+        )
+
     def set_isolation_level(self, connection, level):
         # adjust for ConnectionFairy being present
         # allows attribute set e.g. "connection.autocommit = True"