SQLAlchemy: Add support for 'autogenerate_uuid' in column creation

CHANGES.txt

@@ -5,6 +5,7 @@ Changes for crate
 Unreleased
 ==========
 
+- Add support for CrateDB's gen_random_text_uuid in SQLAlchemy column generation ORM
 - Properly handle Python-native UUID types in SQL parameters
 - SQLAlchemy: Fix handling URL parameters ``timeout`` and ``pool_size``
 - Permit installation with urllib3 v2, see also `urllib3 v2.0 roadmap`_

docs/sqlalchemy.rst

@@ -207,6 +207,7 @@ system <sa:orm_declarative_mapping>`:
     ...     quote_ft = sa.Column(sa.String)
     ...     even_more_details = sa.Column(sa.String, crate_columnstore=False)
     ...     created_at = sa.Column(sa.DateTime, server_default=sa.func.now())
+    ...     uuid = sa.Column(sa.String, crate_autogenerate_uuid=True)
     ...
     ...     __mapper_args__ = {
     ...         'exclude_properties': ['name_ft', 'quote_ft']
@@ -230,6 +231,8 @@ In this example, we:
   the mapping (so SQLAlchemy doesn't try to update them as if they were columns)
 - Disable the columnstore of the ``even_more_details`` column using ``crate_columnstore=False``
 - Add a ``created_at`` column whose default value is set by CrateDB's ``now()`` function.
+- Add a ``uuid`` column whose default value is generated by CrateDB's ``gen_random_text_uuid``
+  can also be used with ``primary_key=True`` as an alternative of ``default=gen_key``
 
 .. TIP::
 

src/crate/client/sqlalchemy/compiler.py

@@ -116,6 +116,22 @@ def get_column_specification(self, column, **kwargs):
         if column.computed is not None:
             colspec += " " + self.process(column.computed)
 
+        if column.dialect_options['crate'].get('autogenerate_uuid'):
+            if not isinstance(column.type, (sa.String, sa.Text)):
+                raise sa.exc.CompileError(
+                    "Auto generate uuid is only supported for column"
+                    "types STRING and TEXT"
+                )
+            if default is not None:
+                raise sa.exc.CompileError(
+                    "Can only have one default value but server_default"
+                    " and crate_generate_uuid are set"
+                )
+
+            colspec += " DEFAULT gen_random_text_uuid()"
+
+        # nullable should go after 'DEFAULT' query modifications, otherwise
+        # invalid statements will be generated, ex: `x STRING NOT NULL DEFAULT 'value'`
         if column.nullable is False:
             colspec += " NOT NULL"
         elif column.nullable and column.primary_key:

src/crate/client/sqlalchemy/tests/create_table_test.py

@@ -311,3 +311,36 @@
              'pk STRING NOT NULL, \n\t'
              'answer INT DEFAULT 42, \n\t'
              'PRIMARY KEY (pk)\n)\n\n'), ())
+
+    def test_column_autogenerate_uuid(self):
+        class DummyTable(self.Base):
+            __tablename__ = 't'
+            pk = sa.Column(sa.String, primary_key=True, crate_autogenerate_uuid=True)
+            other = sa.Column(sa.Boolean)
+
+        self.Base.metadata.create_all(bind=self.engine)
+        fake_cursor.execute.assert_called_with(
+            '\nCREATE TABLE t (\n\t'
+            'pk STRING DEFAULT gen_random_text_uuid() NOT NULL, \n\t'
+            'other BOOLEAN, \n\tPRIMARY KEY (pk)\n)\n\n', ()
+        )
+
+    def test_column_autogenerate_uuid_correct_type(self):
+        class DummyTable(self.Base):
+            __tablename__ = 't'
+            pk = sa.Column(sa.Integer, primary_key=True, crate_autogenerate_uuid=True)
+            other = sa.Column(sa.Boolean)
+
+        with self.assertRaises(sa.exc.CompileError):
+            self.Base.metadata.create_all(bind=self.engine)
+
+    def test_column_autogenerate_uuid_clashes_with_server_default(self):
+        class DummyTable(self.Base):
+            __tablename__ = 't'
+            pk = sa.Column(sa.String, primary_key=True,
+                           crate_autogenerate_uuid=True,
+                           server_default='value')
+            other = sa.Column(sa.Boolean)
+
+        with self.assertRaises(sa.exc.CompileError):
+            self.Base.metadata.create_all(bind=self.engine)