[AIRFLOW-1522] Increase text size for var field in variables for MySQL

Closes apache#2535 from saguziel/aguziel-increase-text

airflow/migrations/versions/d2ae31099d61_increase_text_size_for_mysql.py

@@ -0,0 +1,41 @@
+#
+# Licensed 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.
+
+"""Increase text size for MySQL (not relevant for other DBs' text types)
+
+Revision ID: d2ae31099d61
+Revises: 947454bf1dff
+Create Date: 2017-08-18 17:07:16.686130
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = 'd2ae31099d61'
+down_revision = '947454bf1dff'
+branch_labels = None
+depends_on = None
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import mysql
+from alembic import context
+
+
+def upgrade():
+    if context.config.get_main_option('sqlalchemy.url').startswith('mysql'):
+        op.alter_column(table_name='variable', column_name='val', type_=mysql.MEDIUMTEXT)
+
+
+def downgrade():
+    if context.config.get_main_option('sqlalchemy.url').startswith('mysql'):
+        op.alter_column(table_name='variable', column_name='val', type_=mysql.TEXT)