2 files changed, 37 insertions, 1 deletions
diff --git a/db/post_migrate/20171114104051_remove_empty_fork_networks.rb b/db/post_migrate/20171114104051_remove_empty_fork_networks.rb
new file mode 100644
index 00000000000..2fe99a1b9c1
--- /dev/null
+++ b/db/post_migrate/20171114104051_remove_empty_fork_networks.rb
@@ -0,0 +1,36 @@
+class RemoveEmptyForkNetworks < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  BATCH_SIZE = 10_000
+
+  class MigrationForkNetwork < ActiveRecord::Base
+    include EachBatch
+
+    self.table_name = 'fork_networks'
+  end
+
+  class MigrationForkNetworkMembers < ActiveRecord::Base
+    self.table_name = 'fork_network_members'
+  end
+
+  disable_ddl_transaction!
+
+  def up
+    say 'Deleting empty ForkNetworks in batches'
+
+    has_members = MigrationForkNetworkMembers
+                    .where('fork_network_members.fork_network_id = fork_networks.id')
+                    .select(1)
+    MigrationForkNetwork.where('NOT EXISTS (?)', has_members)
+      .each_batch(of: BATCH_SIZE) do |networks|
+      deleted = networks.delete_all
+
+      say "Deleted #{deleted} rows in batch"
+    end
+  end
+
+  def down
+    # nothing
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 37e08d453c8..53299792a39 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20171106180641) do
+ActiveRecord::Schema.define(version: 20171114104051) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"