Java（HBase）API：如何知道以字节存储的值的数据类型 [英] Java(HBase) API: How to know the data type of a value stored in bytes

问题描述

使用HBase Java API时，我有一行代码如下：

  byte [] value = scanner .next（）。getValue（Bytes.toBytes（family），Bytes.toBytes（qualifier））; 
  

假设我不知道这是一个Int或String类型的值，应该在 Byte.toInt（value）和 Byte.toString（value）之间使用以正确打印值？

这不是一个真正的HBase / Hadoop问题，而是一个Java问题，但我使用Google搜索并找不到获取它的方法。有可能知道吗？

从HBase Java API的另一个方向，我如何知道存储在family：qualifier中的给定值的数据类型？

感谢！ t支持键入列，数据存储区跟踪所存储数据的类型。 HBase本身并没有跟踪 - 所以没有办法本地告诉 - 存储在列中的数据的类型。使用HBase的开发人员负责自行跟踪列数据类型。

对于许多应用程序，应用程序可以对这些类型进行硬编码的每列。通过这种方式，HBase表往往比RDBMS表更适用于特定应用程序。开发人员还可以为该行创建专用于数据类型模式的列族或列（例如，将Avro模式序列化为字符串）。

HBase文档体系结构页面解释了HBase和传统RDBMS在这里的差异：

https://hbase.apache.org/book/architecture.html#arch.overview.when

when working with HBase Java API, I have a line of the code as below:

byte[] value = scanner.next().getValue(Bytes.toBytes(family), Bytes.toBytes(qualifier));

Assume I don't know if it's a Int or String type for this value, which should I use between Byte.toInt(value) and Byte.toString(value) to print the value correctly?

This is not a really HBase/Hadoop question, and rather a Java one, but I googled and can't find a way to get it. Is it possible to know it?

In another direction, from the HBase Java API, how can I know the data type for a given value stored in a family:qualifier?

Thanks!

解决方案

Unlike a traditional RDBMS, HBase doesn't support "typed columns", where the data store keeps track of the types of data being stored. HBase does not natively keep track of - so there is no way to natively tell - the type of data stored in a column. The developer using HBase is responsible for keep track of column data types on their own.

For many applications, it is acceptable for the application to "hard-code" the types of each column. In this way, HBase tables tend to be more application-specific than RDBMS tables. A developer can also create a column family or column dedicated to a data type schema for the row (for example, an Avro schema serialized as a string).

The HBase documentation's "Architecture" pages explains the differences between HBase and a traditional RDBMS a bit more here:

https://hbase.apache.org/book/architecture.html#arch.overview.when

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