From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Thu, 10 Jan 2013 21:20:57 +0000 (-0500)
Subject: The "implicit" constraint generated by a
X-Git-Tag: rel_0_4_2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b3bc2d877e9e23b35c2ec92645d5cd055468dbd1;p=thirdparty%2Fsqlalchemy%2Falembic.git

The "implicit" constraint generated by a
type such as Boolean or Enum will not generate an
ALTER statement when run on SQlite, which does not
support ALTER for the purpose of adding/removing
constraints separate from the column def itself.
While SQLite supports adding a CHECK constraint
at the column level, SQLAlchemy would need modification
to support this.
A warning is emitted indicating this
constraint cannot be added in this scenario.
#98
---

diff --git a/alembic/ddl/sqlite.py b/alembic/ddl/sqlite.py
index 09437137..df92d960 100644
--- a/alembic/ddl/sqlite.py
+++ b/alembic/ddl/sqlite.py
@@ -1,5 +1,44 @@
 from alembic.ddl.impl import DefaultImpl
+from alembic import util
+
+#from sqlalchemy.ext.compiler import compiles
+#from alembic.ddl.base import AddColumn, alter_table
+#from sqlalchemy.schema import AddConstraint
 
 class SQLiteImpl(DefaultImpl):
     __dialect__ = 'sqlite'
     transactional_ddl = True
+
+    def add_constraint(self, const):
+        # attempt to distinguish between an
+        # auto-gen constraint and an explicit one
+        if const._create_rule is None:
+            raise NotImplementedError(
+                    "No support for ALTER of constraints in SQLite dialect")
+        elif const._create_rule(self):
+            util.warn("Skipping unsupported ALTER for "
+                        "creation of implicit constraint")
+
+
+    def drop_constraint(self, const):
+        if const._create_rule is None:
+            raise NotImplementedError(
+                    "No support for ALTER of constraints in SQLite dialect")
+
+
+#@compiles(AddColumn, 'sqlite')
+#def visit_add_column(element, compiler, **kw):
+#    return "%s %s" % (
+#        alter_table(compiler, element.table_name, element.schema),
+#        add_column(compiler, element.column, **kw)
+#    )
+
+
+#def add_column(compiler, column, **kw):
+#    text = "ADD COLUMN %s" % compiler.get_column_specification(column, **kw)
+#    # need to modify SQLAlchemy so that the CHECK associated with a Boolean
+#    # or Enum gets placed as part of the column constraints, not the Table
+#    # see ticket 98
+#    for const in column.constraints:
+#        text += compiler.process(AddConstraint(const))
+#    return text
diff --git a/docs/build/changelog.rst b/docs/build/changelog.rst
index 1dae555b..52087d71 100644
--- a/docs/build/changelog.rst
+++ b/docs/build/changelog.rst
@@ -8,6 +8,21 @@ Changelog
 .. changelog::
     :version: 0.4.2
 
+    .. change::
+        :tags: bug, sqlite
+        :tickets: 98
+
+      The "implicit" constraint generated by a
+      type such as Boolean or Enum will not generate an
+      ALTER statement when run on SQlite, which does not
+      support ALTER for the purpose of adding/removing
+      constraints separate from the column def itself.
+      While SQLite supports adding a CHECK constraint
+      at the column level, SQLAlchemy would need modification
+      to support this.
+      A warning is emitted indicating this
+      constraint cannot be added in this scenario.
+
     .. change::
         :tags: bug
         :tickets: 96
diff --git a/tests/test_sqlite.py b/tests/test_sqlite.py
new file mode 100644
index 00000000..8d514eeb
--- /dev/null
+++ b/tests/test_sqlite.py
@@ -0,0 +1,42 @@
+from tests import op_fixture, assert_raises_message
+from alembic import op, util
+from sqlalchemy import Integer, Column, ForeignKey, \
+            UniqueConstraint, Table, MetaData, String,\
+            func, Boolean
+from sqlalchemy.sql import table, column
+
+def test_add_column():
+    context = op_fixture('sqlite')
+    op.add_column('t1', Column('c1', Integer))
+    context.assert_(
+        'ALTER TABLE t1 ADD COLUMN c1 INTEGER'
+    )
+
+def test_add_column_implicit_constraint():
+    context = op_fixture('sqlite')
+    op.add_column('t1', Column('c1', Boolean))
+    context.assert_(
+        'ALTER TABLE t1 ADD COLUMN c1 BOOLEAN'
+    )
+
+def test_add_explicit_constraint():
+    context = op_fixture('sqlite')
+    assert_raises_message(
+        NotImplementedError,
+        "No support for ALTER of constraints in SQLite dialect",
+        op.create_check_constraint,
+        "foo",
+        "sometable",
+        column('name') > 5
+    )
+
+def test_drop_explicit_constraint():
+    context = op_fixture('sqlite')
+    assert_raises_message(
+        NotImplementedError,
+        "No support for ALTER of constraints in SQLite dialect",
+        op.drop_constraint,
+        "foo",
+        "sometable",
+    )
+