You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: consistency_check.rs
    path of file: ./repos/tikv/src/storage/mvcc
    
    the code of the file until where you have to start completion: // Copyright 2020 TiKV Project Authors. Licensed under Apache-2.0.

// #[PerformanceCriticalPath] called by raftstore
use std::{
    cmp::Ordering,
    convert::TryInto,
    marker::PhantomData,
    sync::{
        atomic::{AtomicU64, Ordering as A
    
    fn on_default(&mut self, key: &[u8], value: &[u8]) -> Result<bool> {
        let (prefix, start_ts) = box_try!(Key::split_on_ts_for(key));
        if prefix != AsRef::<[u8]>::as_ref(&self.current_item) {
            return Ok(false);
        }

        if !self.committed_txns_sorted {
            self.committed_txns.sort_unstable();
            self.committed_txns_sorted = true;
        }

        let start_ts = start_ts.into_inner();
        if start_ts > self.safe_point && self.committed_txns.binary_search(&start_ts).is_ok() {
            self.digest.update(key);
            self.digest.update(value);
        }
        Ok(true)
    }