[GitHub] [beam] lostluck commented on a change in pull request #12024: [BEAM-9679] Add Side Input to Core Transform Go SDK katas

[GitBox <gi...@apache.org>]

lostluck commented on a change in pull request #12024:
URL: https://github.com/apache/beam/pull/12024#discussion_r441691646



##########
File path: learning/katas/go/Core Transforms/Side Input/Side Input/pkg/task/task.go
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@@ -0,0 +1,45 @@
+// Licensed to the Apache Software Foundation (ASF) under one or more
+// contributor license agreements.  See the NOTICE file distributed with
+// this work for additional information regarding copyright ownership.
+// The ASF licenses this file to You under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance with
+// the License.  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package task
+
+import (
+	"github.com/apache/beam/sdks/go/pkg/beam"
+)
+
+type Person struct {
+	Name, City, Country string
+}
+
+func ApplyTransform(s beam.Scope, personsKV beam.PCollection, citiesToCountries beam.PCollection) beam.PCollection {
+	citiesToCountriesView := beam.SideInput{
+		Input: citiesToCountries,
+	}
+	return beam.ParDo(s, joinFn, personsKV, citiesToCountriesView)
+}
+
+func joinFn(person Person, citiesToCountriesIter func(*string, *string) bool, emit func(Person)) {
+	var city, country string
+	for citiesToCountriesIter(&city, &country) {

Review comment:
       This is the only Side Input iterating KV API in the Go SDK at present.
   
   While [generics in Go are making progress](https://blog.golang.org/generics-next-step) it's not something we can use at this time. Maybe late next year, we'll be able to add a beam.KV type.
   
   Further, sideinputs are not guaranteed grouped or ordered in any way, so we'd be getting pairs in one form or another regardless.




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