Change meter.resource_metadata column type

The existing schema limits for meter.resource_metadata column to
5000 characters, which may not be enough for a large metadata
payload encoded as JSON.
Using a Text column will let us store an arbitrary amount of data
in that column without worrying about overflowing.

Closes-Bug: #1204638

Change-Id: I5eb1cdbb3d4770a8348682634a78ccb0f843c141

ceilometer/storage/sqlalchemy/alembic/versions/17738166b91_fix_meter_resource_m.py

@@ -0,0 +1,50 @@
+# -*- encoding: utf-8 -*-
+#
+# Authors: Svetlana Shturm <sshturm@mirantis.com>
+#
+# 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.
+"""fix_meter_resource_metadata_type
+
+Revision ID: 17738166b91
+Revises: 43b1a023dfaa
+Create Date: 2013-08-08 11:20:56.514012
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '17738166b91'
+down_revision = '43b1a023dfaa'
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def change_type(type):
+    column_old = 'resource_metadata'
+    column_new = column_old + '_new'
+    bind = op.get_bind()
+    meta = sa.MetaData(bind.engine)
+    meter = sa.Table('meter', meta, autoload=True)
+    new_column = sa.Column(column_new, type)
+    new_column.create(meter)
+    meter.update().values(resource_metadata_new=meter.c[column_old]).execute()
+    meter.c[column_old].drop()
+    meter.c[column_new].alter(name=column_old)
+
+
+def upgrade():
+    change_type(sa.Text)
+
+
+def downgrade():
+    change_type(sa.Stryng(5000))

ceilometer/storage/sqlalchemy/models.py

@@ -127,7 +127,7 @@ class Meter(Base):
     user_id = Column(String(255), ForeignKey('user.id'))
     project_id = Column(String(255), ForeignKey('project.id'))
     resource_id = Column(String(255), ForeignKey('resource.id'))
-    resource_metadata = Column(JSONEncodedDict(5000))
+    resource_metadata = Column(JSONEncodedDict())
     counter_type = Column(String(255))
     counter_unit = Column(String(255))
     counter_volume = Column(Float(53))