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.

2 files changed, 40 insertions, 1 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
diff --git a/db/schema.rb b/db/schema.rb
index 023eee5f33e..0fb31ce2ef2 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20190204115450) do
+ActiveRecord::Schema.define(version: 20190211131150) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -1046,6 +1046,7 @@ ActiveRecord::Schema.define(version: 20190204115450) do
     t.boolean "discussion_locked"
     t.datetime_with_timezone "closed_at"
     t.integer "closed_by_id"
+    t.integer "state_id", limit: 2
     t.index ["author_id"], name: "index_issues_on_author_id", using: :btree
     t.index ["closed_by_id"], name: "index_issues_on_closed_by_id", using: :btree
     t.index ["confidential"], name: "index_issues_on_confidential", using: :btree
@@ -1283,6 +1284,7 @@ ActiveRecord::Schema.define(version: 20190204115450) do
     t.string "rebase_commit_sha"
     t.boolean "squash", default: false, null: false
     t.boolean "allow_maintainer_to_push"
+    t.integer "state_id", limit: 2
     t.index ["assignee_id"], name: "index_merge_requests_on_assignee_id", using: :btree
     t.index ["author_id"], name: "index_merge_requests_on_author_id", using: :btree
     t.index ["created_at"], name: "index_merge_requests_on_created_at", using: :btree