MVCC相关源码：
在HBase put源码中 http://blackproof.iteye.com/blog/2197710
有mvcc用hregion的mvcc的write point，在生成mvcc的readpoint
KeyValueHeap类的next获取cell的时候使用keyvalue的mvcc的readpoint，判断是否取当前kv
/**
* Gets the next row of keys from the top-most scanner.
* <p>
* This method takes care of updating the heap.
* <p>
* This can ONLY be called when you are using Scanners that implement
* InternalScanner as well as KeyValueScanner (a {@link StoreScanner}).
* @param result
* @param limit
* @return true if there are more keys, false if all scanners are done
*/
public boolean next(List<Cell> result, int limit) throws IOException {
if (this.current == null) {
return false;
}
InternalScanner currentAsInternal = (InternalScanner)this.current;
boolean mayContainMoreRows = currentAsInternal.next(result, limit);
KeyValue pee = this.current.peek();
/*
* By definition, any InternalScanner must return false only when it has no
* further rows to be fetched. So, we can close a scanner if it returns
* false. All existing implementations seem to be fine with this. It is much
* more efficient to close scanners which are not needed than keep them in
* the heap. This is also required for certain optimizations.
*/
if (pee == null || !mayContainMoreRows) {
this.current.close();
} else {
this.heap.add(this.current);
}
this.current = pollRealKV();
return (this.current != null);
}
