fix(db): set slices.query_context to MEDIUMTEXT for mysql (apache#20779)

superset/migrations/versions/2022-07-19_15-16_a39867932713_query_context_to_mediumtext.py

@@ -0,0 +1,44 @@
+# 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.
+"""query_context_to_mediumtext
+
+Revision ID: a39867932713
+Revises: 06e1e70058c7
+Create Date: 2022-07-19 15:16:06.091961
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = "a39867932713"
+down_revision = "06e1e70058c7"
+
+from alembic import op
+from sqlalchemy.dialects.mysql.base import MySQLDialect
+
+
+def upgrade():
+    if isinstance(op.get_bind().dialect, MySQLDialect):
+        # If the columns are already MEDIUMTEXT, this is a no-op
+        op.execute("ALTER TABLE slices MODIFY params MEDIUMTEXT")
+        op.execute("ALTER TABLE slices MODIFY query_context MEDIUMTEXT")
+
+
+def downgrade():
+    # It's Okay to keep these columns as MEDIUMTEXT
+    # Since some oraganizations may have already manually changed the type
+    # and downgrade may loose data so we don't do it.
+    pass