hadoop - 同时使用 Delete 和 Put 时无法在 HBase 中插入新数据

Question

我正在使用 Hbase mapreduce 来计算报告。在 reducer 中，我尝试清除“result”列族，然后添加一个新的“total”列。但我发现列族是删除的，但新数据不是插入的。 Put 操作似乎不起作用。你知道为什么吗？

reducer 类中的示例代码:

      Delete del = new Delete(rowkey.getBytes());
      del.addFamily(RESULT);
      context.write(new ImmutableBytesWritable(Bytes.toBytes(key.toString())), del);
      Put put = new Put(rowkey.getBytes());
      put.addColumn(RESULT, TOTAL, totalNum);
      context.write(new ImmutableBytesWritable(Bytes.toBytes(key.toString())), put);

Answer 1

是hbase的限制: Deletes mask Puts

27.3.1. Deletes mask Puts Deletes mask puts, even puts that happened after the delete was entered. See HBASE-2256. Remember that a delete writes a tombstone, which only disappears after then next major compaction has run. Suppose you do a delete of everything ⇐ T. After this you do a new put with a timestamp ⇐ T. This put, even if it happened after the delete, will be masked by the delete tombstone. Performing the put will not fail, but when you do a get you will notice the put did have no effect. It will start working again after the major compaction has run. These issues should not be a problem if you use always-increasing versions for new puts to a row. But they can occur even if you do not care about time: just do delete and put immediately after each other, and there is some chance they happen within the same millisecond.