code: func (tc *TransactionContext) Cleanup() {
  	//tc.InfoSchema = nil; we cannot do it now, because some operation like handleFieldList depend on this.
  	tc.DirtyDB = nil
  	tc.Binlog = nil
  	tc.History = nil
  	tc.TableDeltaMap = nil
  }
docs: // Cleanup clears up transaction info that no longer use.