Github user huitseeker commented on a diff in the pull request:
https://github.com/apache/spark/pull/8103#discussion_r49298081
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaPairDStream.scala
---
@@ -336,7 +336,8 @@ class JavaPairDStream[K, V](val dstream: DStream[(K,
V)])(
* However, it is applicable to only "invertible reduce functions".
* Hash partitioning is used to generate the RDDs with Spark's default
number of partitions.
* @param reduceFunc associative reduce function
- * @param invReduceFunc inverse function
+ * @param invReduceFunc inverse function; such that for all x,
invertible y:
+ * `invReduceFunc(reduceFunc(x, y), y) = x`
--- End diff --
```
Welcome to Scala version 2.11.7 (OpenJDK 64-Bit Server VM, Java 1.7.0_91).
Type in expressions to have them evaluated.
Type :help for more information.
scala> def f(s1: String, s2: String) = s1 + s2
f: (s1: String, s2: String)String
scala> def fInv(s1: String, s2: String) = s1.stripSuffix(s2)
fInv: (s1: String, s2: String)String
scala> val x = "aaa"
x: String = aaa
scala> val y = "bbb"
y: String = bbb
scala> fInv(f(x, y), y)
res0: String = aaa
scala> fInv(f(x, y), y) === x
<console>:15: error: value === is not a member of String
fInv(f(x, y), y) === x
^
scala> fInv(f(x, y), y) == x
res2: Boolean = true
scala> fInv(f(x, y), x)
res3: String = aaabbb
scala> fInv(f(x, y), x) === y
<console>:15: error: value === is not a member of String
fInv(f(x, y), x) === y
^
scala> fInv(f(x, y), x) == y
res5: Boolean = false
```
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