- Fixed issue where the SQL Server dialect would reflect a string-

or other variable-length column type with unbounded length
by assigning the token ``"max"`` to the
length attribute of the string.   While using the ``"max"`` token
explicitly is supported by the SQL Server dialect, it isn't part
of the normal contract of the base string types, and instead the
length should just be left as None.   The dialect now assigns the
length to None on reflection of the type so that the type behaves
normally in other contexts.
fixes #3504

diff --git a/doc/build/changelog/changelog_11.rst b/doc/build/changelog/changelog_11.rst
index 1f18d6d16dacbc6748dff9bfcca6fb880a74aed8..bb395a826c06ae96905fd223b8138aea48427004 100644 (file)
--- a/doc/build/changelog/changelog_11.rst
+++ b/doc/build/changelog/changelog_11.rst
@@ -21,3 +21,20 @@
 .. changelog::
     :version: 1.1.0b1
 
+    .. change::
+        :tags: bug, mssql
+        :tickets: 3504
+
+        Fixed issue where the SQL Server dialect would reflect a string-
+        or other variable-length column type with unbounded length
+        by assigning the token ``"max"`` to the
+        length attribute of the string.   While using the ``"max"`` token
+        explicitly is supported by the SQL Server dialect, it isn't part
+        of the normal contract of the base string types, and instead the
+        length should just be left as None.   The dialect now assigns the
+        length to None on reflection of the type so that the type behaves
+        normally in other contexts.
+
+        .. seealso::
+
+            :ref:`change_3504`
\ No newline at end of file

diff --git a/doc/build/changelog/migration_11.rst b/doc/build/changelog/migration_11.rst
index 9c046ab9e23a97e958647dc5270ebbda5cbc0af4..f5602a8ad99fed06bf487d4cb34381e826cf3175 100644 (file)
--- a/doc/build/changelog/migration_11.rst
+++ b/doc/build/changelog/migration_11.rst
@@ -94,6 +94,41 @@ Dialect Improvements and Changes - SQLite
 Dialect Improvements and Changes - SQL Server
 =============================================
 
+.. _change_3504:
+
+String / varlength types no longer represent "max" explicitly on reflection
+---------------------------------------------------------------------------
+
+When reflecting a type such as :class:`.String`, :class:`.Text`, etc.
+which includes a length, an "un-lengthed" type under SQL Server would
+copy the "length" parameter as the value ``"max"``::
+
+    >>> from sqlalchemy import create_engine, inspect
+    >>> engine = create_engine('mssql+pyodbc://scott:tiger@ms_2008', echo=True)
+    >>> engine.execute("create table s (x varchar(max), y varbinary(max))")
+    >>> insp = inspect(engine)
+    >>> for col in insp.get_columns("s"):
+    ...     print col['type'].__class__, col['type'].length
+    ...
+    <class 'sqlalchemy.sql.sqltypes.VARCHAR'> max
+    <class 'sqlalchemy.dialects.mssql.base.VARBINARY'> max
+
+The "length" parameter in the base types is expected to be an integer value
+or None only; None indicates unbounded length which the SQL Server dialect
+interprets as "max".   The fix then is so that these lengths come
+out as None, so that the type objects work in non-SQL Server contexts::
+
+    >>> for col in insp.get_columns("s"):
+    ...     print col['type'].__class__, col['type'].length
+    ...
+    <class 'sqlalchemy.sql.sqltypes.VARCHAR'> None
+    <class 'sqlalchemy.dialects.mssql.base.VARBINARY'> None
+
+Applications which may have been relying on a direct comparison of the "length"
+value to the string "max" should consider the value of ``None`` to mean
+the same thing.
+
+:ticket:`3504`
 
 Dialect Improvements and Changes - Oracle
 =============================================

diff --git a/lib/sqlalchemy/dialects/mssql/base.py b/lib/sqlalchemy/dialects/mssql/base.py
index bd41c19bfdb7a93adcc42b78b9e2b7de9eb952f3..6670a28bdc2908659e3033533741f94189d2f0db 100644 (file)
--- a/lib/sqlalchemy/dialects/mssql/base.py
+++ b/lib/sqlalchemy/dialects/mssql/base.py
@@ -1772,7 +1772,7 @@ class MSDialect(default.DefaultDialect):
                            MSNText, MSBinary, MSVarBinary,
                            sqltypes.LargeBinary):
                 if charlen == -1:
-                    charlen = 'max'
+                    charlen = None
                 kwargs['length'] = charlen
                 if collation:
                     kwargs['collation'] = collation

diff --git a/test/dialect/mssql/test_reflection.py b/test/dialect/mssql/test_reflection.py
index bee4415865e92c663c5d75402ddb258cdf31c67d..daf8af724e14b72e3d60481f5a6e7021054d2349 100644 (file)
--- a/test/dialect/mssql/test_reflection.py
+++ b/test/dialect/mssql/test_reflection.py
@@ -1,5 +1,5 @@
 # -*- encoding: utf-8
-from sqlalchemy.testing import eq_
+from sqlalchemy.testing import eq_, is_, in_
 from sqlalchemy import *
 from sqlalchemy import types, schema, event
 from sqlalchemy.databases import mssql
@@ -24,14 +24,14 @@ class ReflectionTest(fixtures.TestBase, ComparesTables):
             Column('user_name', types.VARCHAR(20), nullable=False),
             Column('test1', types.CHAR(5), nullable=False),
             Column('test2', types.Float(5), nullable=False),
-            Column('test3', types.Text('max')),
+            Column('test3', types.Text()),
             Column('test4', types.Numeric, nullable=False),
             Column('test5', types.DateTime),
             Column('parent_user_id', types.Integer,
                    ForeignKey('engine_users.user_id')),
             Column('test6', types.DateTime, nullable=False),
-            Column('test7', types.Text('max')),
-            Column('test8', types.LargeBinary('max')),
+            Column('test7', types.Text()),
+            Column('test8', types.LargeBinary()),
             Column('test_passivedefault2', types.Integer,
                    server_default='5'),
             Column('test9', types.BINARY(100)),
@@ -171,6 +171,32 @@ class ReflectionTest(fixtures.TestBase, ComparesTables):
             set([t2.c['x col'], t2.c.y])
         )
 
+    @testing.provide_metadata
+    def test_max_ident_in_varchar_not_present(self):
+        """test [ticket:3504].
+
+        Here we are testing not just that the "max" token comes back
+        as None, but also that these types accept "max" as the value
+        of "length" on construction, which isn't a directly documented
+        pattern however is likely in common use.
+
+        """
+        metadata = self.metadata
+
+        Table(
+            't', metadata,
+            Column('t1', types.String),
+            Column('t2', types.Text('max')),
+            Column('t3', types.Text('max')),
+            Column('t4', types.LargeBinary('max')),
+            Column('t5', types.VARBINARY('max')),
+        )
+        metadata.create_all()
+        for col in inspect(testing.db).get_columns('t'):
+            is_(col['type'].length, None)
+            in_('max', str(col['type'].compile(dialect=testing.db.dialect)))
+
+
 from sqlalchemy.dialects.mssql.information_schema import CoerceUnicode, tables
 from sqlalchemy.dialects.mssql import base