github.com/apache/beam/sdks/v2@v2.48.2/go/examples/grades/grades.go (about)

     1  // Licensed to the Apache Software Foundation (ASF) under one or more
     2  // contributor license agreements.  See the NOTICE file distributed with
     3  // this work for additional information regarding copyright ownership.
     4  // The ASF licenses this file to You under the Apache License, Version 2.0
     5  // (the "License"); you may not use this file except in compliance with
     6  // the License.  You may obtain a copy of the License at
     7  //
     8  //    http://www.apache.org/licenses/LICENSE-2.0
     9  //
    10  // Unless required by applicable law or agreed to in writing, software
    11  // distributed under the License is distributed on an "AS IS" BASIS,
    12  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  // See the License for the specific language governing permissions and
    14  // limitations under the License.
    15  
    16  package main
    17  
    18  // beam-playground:
    19  //   name: Grades
    20  //   description: An example that combines grades data.
    21  //   multifile: false
    22  //   context_line: 41
    23  //   categories:
    24  //     - Debugging
    25  //     - Combiners
    26  //     - Filtering
    27  //   complexity: MEDIUM
    28  //   tags:
    29  //     - combine
    30  //     - map
    31  //     - strings
    32  //     - numbers
    33  
    34  import (
    35  	"context"
    36  	"flag"
    37  
    38  	"github.com/apache/beam/sdks/v2/go/pkg/beam"
    39  	"github.com/apache/beam/sdks/v2/go/pkg/beam/log"
    40  	"github.com/apache/beam/sdks/v2/go/pkg/beam/register"
    41  	"github.com/apache/beam/sdks/v2/go/pkg/beam/transforms/stats"
    42  	"github.com/apache/beam/sdks/v2/go/pkg/beam/transforms/top"
    43  	"github.com/apache/beam/sdks/v2/go/pkg/beam/x/beamx"
    44  	"github.com/apache/beam/sdks/v2/go/pkg/beam/x/debug"
    45  )
    46  
    47  func init() {
    48  	register.Function2x0(printTopFn)
    49  	register.Function2x1(less)
    50  	register.Function2x1(alphabetically)
    51  	register.Function1x2(keyGrade)
    52  	register.Function1x1(getGPA)
    53  }
    54  
    55  type Grade struct {
    56  	Name string
    57  	GPA  float32
    58  }
    59  
    60  func less(a, b Grade) bool {
    61  	return a.GPA < b.GPA
    62  }
    63  
    64  func alphabetically(a, b Grade) bool {
    65  	return a.Name < b.Name
    66  }
    67  
    68  func printTopFn(ctx context.Context, list []Grade) {
    69  	log.Infof(ctx, "TOP %v student(s):", len(list))
    70  	for i, student := range list {
    71  		log.Infof(ctx, " %v:\t%v\t(GPA: %v)", i+1, student.Name, student.GPA)
    72  	}
    73  }
    74  
    75  func keyGrade(g Grade) (string, Grade) {
    76  	return g.Name[:1], g
    77  }
    78  
    79  func getGPA(g Grade) float32 { return g.GPA }
    80  
    81  func main() {
    82  	flag.Parse()
    83  	beam.Init()
    84  
    85  	ctx := context.Background()
    86  
    87  	data := []Grade{
    88  		{"Adam", 2.3},
    89  		{"Alice", 3.8},
    90  		{"Alex", 2.5},
    91  		{"Bart", 3.2},
    92  		{"Bob", 3.9},
    93  		{"Brittney", 3.1},
    94  		{"Brenda", 3.5},
    95  		{"Chad", 1.1},
    96  	}
    97  
    98  	log.Info(ctx, "Running grades")
    99  
   100  	p := beam.NewPipeline()
   101  	s := p.Root()
   102  	students := beam.CreateList(s, data)
   103  
   104  	// (1) Print top 3 students overall by GPA
   105  
   106  	best := top.Largest(s, students, 3, less)
   107  	beam.ParDo0(s, printTopFn, best)
   108  
   109  	// (2) Print top student per initial (then ordered by name)
   110  
   111  	keyed := beam.ParDo(s, keyGrade, students)
   112  	keyedBest := top.LargestPerKey(s, keyed, 1, less)
   113  	unkeyed := beam.Explode(s, beam.DropKey(s, keyedBest))
   114  
   115  	altBest := top.Smallest(s, unkeyed, 30, alphabetically)
   116  	beam.ParDo0(s, printTopFn, altBest)
   117  
   118  	// (3) Print Chad
   119  
   120  	chad := top.Smallest(s, students, 1, less)
   121  	beam.ParDo0(s, printTopFn, chad)
   122  
   123  	// (4) Print min/max/sum/mean grades
   124  
   125  	grades := beam.ParDo(s, getGPA, students)
   126  	debug.Printf(s, "Min: %v", stats.Min(s, grades))
   127  	debug.Printf(s, "Max: %v", stats.Max(s, grades))
   128  	debug.Printf(s, "Sum: %v", stats.Sum(s, grades))
   129  	debug.Printf(s, "Mean: %v", stats.Mean(s, grades))
   130  
   131  	if err := beamx.Run(ctx, p); err != nil {
   132  		log.Exitf(ctx, "Failed to execute job: %v", err)
   133  	}
   134  }