@Override
    public IndexItem<K> removeIndexItem(StoreTxLogPosition txLogResult, K key) {
        IndexItem<K> value = indexMap.remove(key);
        this.lastTxLog = txLogResult;
        currentChangeNum.incrementAndGet();
        return value;
    }
@author Robert HG (254963746@qq.com) on 12/16/15.
lts-core/src/main/java/com/github/ltsopensource/kv/index/MemIndex.java