1 files changed, 56 insertions, 0 deletions
diff --git a/lib/gitlab/database/partitioning/detached_partition_dropper.rb b/lib/gitlab/database/partitioning/detached_partition_dropper.rb
new file mode 100644
index 00000000000..dc63d93fd07
--- /dev/null
+++ b/lib/gitlab/database/partitioning/detached_partition_dropper.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+module Gitlab
+  module Database
+    module Partitioning
+      class DetachedPartitionDropper
+        def perform
+          return unless Feature.enabled?(:drop_detached_partitions, default_enabled: :yaml)
+
+          Gitlab::AppLogger.info(message: "Checking for previously detached partitions to drop")
+          Postgresql::DetachedPartition.ready_to_drop.find_each do |detached_partition|
+            conn.transaction do
+              # Another process may have already dropped the table and deleted this entry
+              next unless (detached_partition = Postgresql::DetachedPartition.lock.find_by(id: detached_partition.id))
+
+              unless check_partition_detached?(detached_partition)
+                Gitlab::AppLogger.error(message: "Attempt to drop attached database partition", partition_name: detached_partition.table_name)
+                detached_partition.destroy!
+                next
+              end
+
+              drop_one(detached_partition)
+            end
+          rescue StandardError => e
+            Gitlab::AppLogger.error(message: "Failed to drop previously detached partition",
+                                    partition_name: detached_partition.table_name,
+                                    exception_class: e.class,
+                                    exception_message: e.message)
+          end
+        end
+
+        private
+
+        def drop_one(detached_partition)
+          conn.transaction do
+            conn.execute(<<~SQL)
+              DROP TABLE #{Gitlab::Database::DYNAMIC_PARTITIONS_SCHEMA}.#{conn.quote_table_name(detached_partition.table_name)}
+            SQL
+
+            detached_partition.destroy!
+          end
+          Gitlab::AppLogger.info(message: "Dropped previously detached partition", partition_name: detached_partition.table_name)
+        end
+
+        def check_partition_detached?(detached_partition)
+          # PostgresPartition checks the pg_inherits view, so our partition will only show here if it's still attached
+          # and thus should not be dropped
+          !PostgresPartition.for_identifier("#{Gitlab::Database::DYNAMIC_PARTITIONS_SCHEMA}.#{detached_partition.table_name}").exists?
+        end
+
+        def conn
+          @conn ||= ApplicationRecord.connection
+        end
+      end
+    end
+  end
+end