Atomic generation of internal ids for issues.

1 files changed, 35 insertions, 0 deletions

diff --git a/db/migrate/20180305095250_create_internal_ids_table.rb b/db/migrate/20180305095250_create_internal_ids_table.rb
new file mode 100644
index 00000000000..19c1904bb43
--- /dev/null
+++ b/db/migrate/20180305095250_create_internal_ids_table.rb
@@ -0,0 +1,35 @@
+class CreateInternalIdsTable < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    create_table :internal_ids do |t|
+      t.references :project
+      t.integer :usage, null: false
+      t.integer :last_value, null: false
+    end
+
+    unless index_exists?(:internal_ids, [:usage, :project_id])
+      add_index :internal_ids, [:usage, :project_id], unique: true
+    end
+
+    unless foreign_key_exists?(:internal_ids, :project_id)
+      add_concurrent_foreign_key :internal_ids, :projects, column: :project_id, on_delete: :cascade
+    end
+  end
+
+  def down
+    drop_table :internal_ids
+  end
+
+  private
+
+  def foreign_key_exists?(table, column)
+    foreign_keys(table).any? do |key|
+      key.options[:column] == column.to_s
+    end
+  end
+end