Hi Timur,
You can use a composite key [1] to compare keys consisting of multiple fields.
For example:
```
val a = env.fromCollection(Seq(Thing("a", "b"), Thing("c", "d")))
val b = env.fromCollection(Seq(Thing("a", "x"), Thing("z", "m")))
a.coGroup(b)
.where(“f1”, “f2”) // Flink compares the values of f1 first, and compares the
values of f2 if values of f1 are same.
.equalTo(“f1”, “f2”) { // Note that you must specify same number of keys
(left, right) => 1
}
```
Composite key can be applied to Scala tuple also:
```
val a = env.fromCollection(Seq(("a", "b"), ("c", "d")))
val b = env.fromCollection(Seq(("a", "x"), ("z", "m")))
a.coGroup(b)
.where(0, 1) // Note that field numbers start from 0.
.equalTo(0, 1) {
(left, right) => 1
}
```
I hope this helps.
[1]:
https://ci.apache.org/projects/flink/flink-docs-master/apis/common/index.html#define-keys-for-tuples
Regards,
Chiwan Park
> On Mar 30, 2016, at 3:54 AM, Timur Fayruzov <timur.fairu...@gmail.com> wrote:
>
> Hello,
>
> Another issue I have encountered is incorrect implicit resolution (I'm using
> Scala 2.11.7). Here's the example (with a workaround):
> val a = env.fromCollection(Seq(Thing("a", "b"), Thing("c", "d")))
> val b = env.fromCollection(Seq(Thing("a", "x"), Thing("z", "m")))
> a.coGroup(b)
> .where(e => e.f1)
> //.equalTo(e => e) { //this fails to compile because equalTo expects an
> implicit
> .equalTo("f1") {
> (left, right) => 1
> }
> However, the workaround does not quite work when key is a tuple (I suspect
> this applies to other generic classes as well):
> val a = env.fromCollection(Seq(Thing("a", "b"), Thing("c", "d")))
> val b = env.fromCollection(Seq(Thing("a", "x"), Thing("z", "m")))
> a.coGroup(b)
> .where(e => (e.f1, e.f2))
> .equalTo(e => (e.f1, e.f2))(TypeInformation.of(classOf[(String, String)]))
> { (left, right) => 1} // throws InvalidProgramException
> Here, I try to provide the implicit TypeInformation explicitly, but
> apparently it's not compatible with the way implicit inference is done.
> (TypeInformation I generate is GenericType<scala.Tuple2>, while
> scala.Tuple2<String, String> is expected).
>
> Now, I can split this in 2 operations like below:
> val tmp = a.coGroup(b)
> .where(e => (e.f1, e.f2))
> .equalTo(e => (e.f1, e.f2))
>
> tmp { (left, right) => 1}
> but, I would like to avoid adding clutter to my processing logic, and it's
> not entirely clear to me how this would be scheduled.
>
> As an option, I can hash the hell out of my keys like that:
> a.coGroup(b)
> .where(e => (e.f1, e.f2).hashCode)
> .equalTo(e => (e.f1, e.f2).hashCode)(TypeInformation.of(classOf[Int])){
> (left, right) => 1}
> but that, again, adds some indirection and clutter, not mentioning the hassle
> of dealing with collisions (which can be alleviated by using fancy hashes,
> but I'd like to avoid that).
>
> Any insights on what is the way to go here are highly appreciated.
>
> Thanks,
> Timur
