Spark SQL“< =>"操作员 [英] Spark SQL "<=>" operator
问题描述
我最近在一个Scala Spark项目中遇到了这个运算符:< =>". 我在查找有关它的任何文档时遇到了麻烦.有谁知道它是如何工作的，或者知道一些文档吗?
I recently came across this operator: "<=>" in a Scala Spark project. I am having trouble finding any documentation on it. Does any know how it works, or know of some documentation?
我认为这与平等操作有关.
I believe it has something to with equality operations.
谢谢
观察1(2/12/2020)| Spark 2.3.2 我做了一些实验，发现使用< =>"对位于同一位置的数据执行联接会导致随机播放，而"=="则不会.
Observation 1 (2/12/2020) | Spark 2.3.2 I have done some experimentation and noticed that performing joins on co-located data with "<=>" causes a shuffle to happen, while "==" does not.
推荐答案
Checkout the Section "Supported Hive Feature on Spark SQL Programming guide link and you will find it in the list of Hive Operators supported by Spark.
这是它的作用:
- 对于非空操作数，使用EQUAL(=)运算符返回相同的结果
但是:
-
如果两者均为NULL，则返回TRUE
it returns TRUE if both are NULL
如果其中之一为NULL，则返回FALSE
it returns FALSE if one of them is NULL
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