[schema] Ensuring that the slice datasource fields are non-nullable

UPDATING.md

@@ -27,11 +27,15 @@ assists people when migrating to a new version.
   run `pip install superset[presto]` and/or `pip install superset[hive]` as
   required.
 
-* [5445](https://github.com/apache/incubator-superset/pull/5445) : a change 
-which prevents encoding of empty string from form data in the datanbase. 
+* [5445](https://github.com/apache/incubator-superset/pull/5445) : a change
+which prevents encoding of empty string from form data in the database.
 This involves a non-schema changing migration which does potentially impact
 a large number of records. Scheduled downtime may be advised.
 
+* [7114](https://github.com/apache/incubator-superset/pull/7114): a change
+which adds missing non-nullable fields to the slices table. Depending on the
+integrity of the data, manual intervention may be required.
+
 ## Superset 0.31.0
 * boto3 / botocore was removed from the dependency list. If you use s3
 as a place to store your SQL Lab result set or Hive uploads, you may

superset/migrations/versions/1be0344d4b76_slice_non_nullable.py

@@ -0,0 +1,78 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""slice non-nullable
+
+Revision ID: 1be0344d4b76
+Revises: c82ee8a39623
+Create Date: 2019-03-25 10:02:38.055193
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '1be0344d4b76'
+down_revision = 'c82ee8a39623'
+
+from alembic import op
+from sqlalchemy import Integer, String
+
+
+def upgrade():
+
+    # Enforce that the slices.datasource_id, slices.datasource_name, and
+    # slices.datasource_type columns be non-nullable.
+    with op.batch_alter_table('slices') as batch_op:
+        batch_op.alter_column(
+            'slice_id',
+            existing_type=Integer,
+            nullable=False,
+        )
+
+        batch_op.alter_column(
+            'datasource_name',
+            existing_type=String(2000),
+            nullable=False,
+        )
+
+        batch_op.alter_column(
+            'datasource_type',
+            existing_type=String(200),
+            nullable=False,
+        )
+
+
+def downgrade():
+
+    # Forego that the slices.datasource_id, slices.datasource_name, and
+    # slices.datasource_type columns be non-nullable.
+    with op.batch_alter_table('slices') as batch_op:
+        batch_op.alter_column(
+            'slice_id',
+            existing_type=Integer,
+            nullable=True,
+        )
+
+        batch_op.alter_column(
+            'datasource_name',
+            existing_type=String(2000),
+            nullable=True,
+        )
+
+        batch_op.alter_column(
+            'datasource_type',
+            existing_type=String(200),
+            nullable=True,
+        )

superset/models/core.py

@@ -149,9 +149,9 @@ class Slice(Model, AuditMixinNullable, ImportMixin):
     __tablename__ = 'slices'
     id = Column(Integer, primary_key=True)
     slice_name = Column(String(250))
-    datasource_id = Column(Integer)
-    datasource_type = Column(String(200))
-    datasource_name = Column(String(2000))
+    datasource_id = Column(Integer, nullable=False)
+    datasource_type = Column(String(200), nullable=False)
+    datasource_name = Column(String(2000), nullable=False)
     viz_type = Column(String(250))
     params = Column(Text)
     description = Column(Text)