Migrate issuable states to integer patch 1

Patch 1 that migrates issues/merge requests states from integer to string.
On this commit we are only adding the state_id column and syncing it with a backgroud migration.

On Patch 2 the code to use the new integer column will be deployed and the old column will be
removed.

1 files changed, 37 insertions, 0 deletions

diff --git a/db/migrate/20190211131150_add_state_id_to_issuables.rb b/db/migrate/20190211131150_add_state_id_to_issuables.rb
new file mode 100644
index 00000000000..af02aa84afd
--- /dev/null
+++ b/db/migrate/20190211131150_add_state_id_to_issuables.rb
@@ -0,0 +1,37 @@
+class AddStateIdToIssuables < ActiveRecord::Migration[5.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  MIGRATION = 'SyncIssuablesStateId'.freeze
+
+  # TODO - find out how many issues and merge requests in production
+  # to adapt the batch size and delay interval
+  # Keep in mind that the migration will be scheduled for issues and merge requests.
+  BATCH_SIZE = 5000
+  DELAY_INTERVAL = 5.minutes.to_i
+
+  class Issue < ActiveRecord::Base
+    include EachBatch
+
+    self.table_name = 'issues'
+  end
+
+  class MergeRequest < ActiveRecord::Base
+    include EachBatch
+
+    self.table_name = 'merge_requests'
+  end
+
+  def up
+    add_column :issues, :state_id, :integer, limit: 1
+    add_column :merge_requests, :state_id, :integer, limit: 1
+
+    queue_background_migration_jobs_by_range_at_intervals(Issue.where(state_id: nil), MIGRATION, DELAY_INTERVAL, batch_size: BATCH_SIZE)
+    queue_background_migration_jobs_by_range_at_intervals(MergeRequest.where(state_id: nil), MIGRATION, DELAY_INTERVAL, batch_size: BATCH_SIZE)
+  end
+
+  def down
+    remove_column :issues, :state_id
+    remove_column :merge_requests, :state_id
+  end
+end