1 files changed, 86 insertions, 0 deletions
diff --git a/db/post_migrate/20210622045705_finalize_events_bigint_conversion.rb b/db/post_migrate/20210622045705_finalize_events_bigint_conversion.rb
new file mode 100644
index 00000000000..b99a61e8e63
--- /dev/null
+++ b/db/post_migrate/20210622045705_finalize_events_bigint_conversion.rb
@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+class FinalizeEventsBigintConversion < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  TABLE_NAME = 'events'
+
+  def up
+    ensure_batched_background_migration_is_finished(
+      job_class_name: 'CopyColumnUsingBackgroundMigrationJob',
+      table_name: TABLE_NAME,
+      column_name: 'id',
+      job_arguments: [["id"], ["id_convert_to_bigint"]]
+    )
+
+    swap
+  end
+
+  def down
+    swap
+  end
+
+  private
+
+  def swap
+    # This is to replace the existing "events_pkey" PRIMARY KEY, btree (id)
+    add_concurrent_index TABLE_NAME, :id_convert_to_bigint, unique: true, name: 'index_events_on_id_convert_to_bigint'
+    # This is to replace the existing "index_events_on_project_id_and_id" btree (project_id, id)
+    add_concurrent_index TABLE_NAME, [:project_id, :id_convert_to_bigint], name: 'index_events_on_project_id_and_id_convert_to_bigint'
+    # This is to replace the existing "index_events_on_project_id_and_id_desc_on_merged_action" btree (project_id, id DESC) WHERE action = 7
+    add_concurrent_index TABLE_NAME, [:project_id, :id_convert_to_bigint], order: { id_convert_to_bigint: :desc },
+      where: "action = 7", name: 'index_events_on_project_id_and_id_bigint_desc_on_merged_action'
+
+    # Add a FK on `push_event_payloads(event_id)` to `id_convert_to_bigint`, the old FK (fk_36c74129da)
+    # will be removed when events_pkey constraint is droppped.
+    fk_event_id = concurrent_foreign_key_name(:push_event_payloads, :event_id)
+    fk_event_id_tmp = "#{fk_event_id}_tmp"
+    add_concurrent_foreign_key :push_event_payloads, TABLE_NAME,
+      column: :event_id, target_column: :id_convert_to_bigint,
+      name: fk_event_id_tmp, on_delete: :cascade, reverse_lock_order: true
+
+    with_lock_retries(raise_on_exhaustion: true) do
+      # We'll need  ACCESS EXCLUSIVE lock on the related tables,
+      # lets make sure it can be acquired from the start.
+      # Lock order should be
+      #   1. events
+      #   2. push_event_payloads
+      # in order to match the order in EventCreateService#create_push_event,
+      # and avoid deadlocks.
+      execute "LOCK TABLE #{TABLE_NAME}, push_event_payloads IN ACCESS EXCLUSIVE MODE"
+
+      # Swap column names
+      temp_name = 'id_tmp'
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:id)} TO #{quote_column_name(temp_name)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:id_convert_to_bigint)} TO #{quote_column_name(:id)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(temp_name)} TO #{quote_column_name(:id_convert_to_bigint)}"
+
+      # We need to update the trigger function in order to make PostgreSQL to
+      # regenerate the execution plan for it. This is to avoid type mismatch errors like
+      # "type of parameter 15 (bigint) does not match that when preparing the plan (integer)"
+      function_name = Gitlab::Database::UnidirectionalCopyTrigger.on_table(TABLE_NAME).name(:id, :id_convert_to_bigint)
+      execute "ALTER FUNCTION #{quote_table_name(function_name)} RESET ALL"
+
+      # Swap defaults
+      execute "ALTER SEQUENCE events_id_seq OWNED BY #{TABLE_NAME}.id"
+      change_column_default TABLE_NAME, :id, -> { "nextval('events_id_seq'::regclass)" }
+      change_column_default TABLE_NAME, :id_convert_to_bigint, 0
+
+      # Swap PK constraint
+      execute "ALTER TABLE #{TABLE_NAME} DROP CONSTRAINT events_pkey CASCADE" # this will drop fk_36c74129da
+      rename_index TABLE_NAME, 'index_events_on_id_convert_to_bigint', 'events_pkey'
+      execute "ALTER TABLE #{TABLE_NAME} ADD CONSTRAINT events_pkey PRIMARY KEY USING INDEX events_pkey"
+
+      # Rename the rest of the indexes (we already hold an exclusive lock, so no need to use DROP INDEX CONCURRENTLY here
+      execute 'DROP INDEX index_events_on_project_id_and_id'
+      rename_index TABLE_NAME, 'index_events_on_project_id_and_id_convert_to_bigint', 'index_events_on_project_id_and_id'
+      execute 'DROP INDEX index_events_on_project_id_and_id_desc_on_merged_action'
+      rename_index TABLE_NAME, 'index_events_on_project_id_and_id_bigint_desc_on_merged_action', 'index_events_on_project_id_and_id_desc_on_merged_action'
+
+      # Change the name of the temporary FK
+      rename_constraint(:push_event_payloads, fk_event_id_tmp, fk_event_id)
+    end
+  end
+end