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wordcount.go
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wordcount.go
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// 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 wordcount contains transforms for wordcount.
package wordcount
import (
"context"
"regexp"
"strings"
"fmt"
"github.com/apache/beam/sdks/v2/go/pkg/beam"
"github.com/apache/beam/sdks/v2/go/pkg/beam/io/textio"
"github.com/apache/beam/sdks/v2/go/pkg/beam/testing/passert"
"github.com/apache/beam/sdks/v2/go/pkg/beam/transforms/stats"
)
var (
wordRE = regexp.MustCompile(`[a-zA-Z]+('[a-z])?`)
empty = beam.NewCounter("extract", "emptyLines")
lineLen = beam.NewDistribution("extract", "lineLenDistro")
smallWords = beam.NewCounter("extract", "smallWords")
)
func init() {
beam.RegisterFunction(extractFn)
beam.RegisterFunction(formatFn)
}
// CountWords is a composite transform that counts the words of a PCollection
// of lines. It expects a PCollection of type string and returns a PCollection
// of type KV<string,int>. The Beam type checker enforces these constraints
// during pipeline construction.
func CountWords(s beam.Scope, lines beam.PCollection) beam.PCollection {
s = s.Scope("CountWords")
// Convert lines of text into individual words.
col := beam.ParDo(s, extractFn, lines)
// Count the number of times each word occurs.
return stats.Count(s, col)
}
// extractFn is a DoFn that emits the words in a given line.
func extractFn(ctx context.Context, line string, emit func(string)) {
lineLen.Update(ctx, int64(len(line)))
if len(strings.TrimSpace(line)) == 0 {
empty.Inc(ctx, 1)
}
for _, word := range wordRE.FindAllString(line, -1) {
if len(word) < 6 {
smallWords.Inc(ctx, 1)
}
emit(word)
}
}
// Format formats a KV of a word and its count as a string.
func Format(s beam.Scope, counted beam.PCollection) beam.PCollection {
return beam.ParDo(s, formatFn, counted)
}
func formatFn(w string, c int) string {
return fmt.Sprintf("%s: %v", w, c)
}
// WordCount returns a self-validating wordcount pipeline.
func WordCount(glob, hash string, size int) *beam.Pipeline {
p, s := beam.NewPipelineWithRoot()
in := textio.Read(s, glob)
WordCountFromPCol(s, in, hash, size)
return p
}
// WordCountFromPCol counts the words from a PCollection and validates it.
func WordCountFromPCol(s beam.Scope, in beam.PCollection, hash string, size int) {
out := Format(s, CountWords(s, in))
passert.Hash(s, out, "out", hash, size)
}