henryken commented on a change in pull request #12024: URL: https://github.com/apache/beam/pull/12024#discussion_r441564315
########## File path: learning/katas/go/Core Transforms/Side Input/Side Input/task.md ########## @@ -0,0 +1,68 @@ +<!-- + 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. +--> + +# Side Input + +In addition to the main input PCollection, you can provide additional inputs to a ParDo transform +in the form of side inputs. A side input is an additional input that your DoFn can access each time +it processes an element in the input PCollection. When you specify a side input, you create a view +of some other data that can be read from within the ParDo transform’s DoFn while processing each +element. + +Side inputs are useful if your ParDo needs to inject additional data when processing each element +in the input PCollection, but the additional data needs to be determined at runtime (and not +hard-coded). Such values might be determined by the input data, or depend on a different branch of +your pipeline. + +**Kata:** Please enrich each Person with the country based on the city he/she lives in. + +<div class="hint"> + Use <a href="https://godoc.org/github.com/apache/beam/sdks/go/pkg/beam#hdr-Side_Inputs";> + beam.SideInput</a> to create a side input of the citiesToCountries PCollection +</div> + +<div class="hint"> + Use <a href="https://godoc.org/github.com/apache/beam/sdks/go/pkg/beam#ParDo";> + beam.ParDo</a> with a DoFn that accepts a + <a href="https://godoc.org/github.com/apache/beam/sdks/go/pkg/beam#hdr-Side_Inputs";> + beam.SideInput</a>. +</div> + +<div class="hint"> + Refer to the Beam Programming Guide + <a href="https://beam.apache.org/documentation/programming-guide/#side-inputs";>"Side inputs"</a> + section for more information. +</div> + +<div class="hint"> + A ParDo that has a PCollection KV as side input expects a DoFn that looks like the following. + + ``` Review comment: This code snippet needs to have no indentation to render properly. ########## File path: learning/katas/go/Core Transforms/Side Input/Side Input/pkg/task/task.go ########## @@ -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: Is there a way to use a KV-like API (e.g. get(key)) instead of iterating each of the KV pair? The way this works seems like a List collection with a tuple. Or probably the naming KV is misleading? ########## File path: learning/katas/go/Core Transforms/Side Input/Side Input/pkg/task/task.go ########## @@ -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) { + if person.City == city { + emit(Person{ + Name: person.Name, + City: city, + Country: country, + }) Review comment: Add `break` statement here? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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