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reduce.go
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reduce.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 woker
import (
"context"
"encoding/json"
"fmt"
"os"
"sort"
"github.com/RoaringBitmap/roaring"
"github.com/CocaineCong/tangseng/app/index_platform/repository/storage"
"github.com/CocaineCong/tangseng/consts"
"github.com/CocaineCong/tangseng/idl/pb/mapreduce"
"github.com/CocaineCong/tangseng/types"
)
func reducer(ctx context.Context, task *mapreduce.MapReduceTask, reducef func(string, []string) *roaring.Bitmap) {
// 先从filepath读取intermediate的KeyValue
intermediate := *readFromLocalFile(task.Intermediates)
// 根据kv排序 shuffle 过程
sort.Sort(types.ByKey(intermediate))
dir, _ := os.Getwd()
outName := fmt.Sprintf("%s/mr-tmp-%d.%s",
dir, task.TaskNumber, consts.InvertedBucket)
invertedDB := storage.NewInvertedDB(outName)
var outByte []byte
i := 0
for i < len(intermediate) {
// 将相同的key放在一起分组合并
j := i + 1
for j < len(intermediate) && intermediate[j].Key == intermediate[i].Key {
j++
}
var values []string
for k := i; k < j; k++ {
values = append(values, intermediate[k].Value)
}
// 交给reducef,拿到结果
output := reducef(intermediate[i].Key, values)
// 落倒排索引库
outByte, _ = output.MarshalBinary()
_ = invertedDB.StoragePostings(intermediate[i].Key, outByte)
i = j
}
task.Output = outName
_, err := TaskCompleted(ctx, task)
if err != nil {
fmt.Println("reducer-TaskCompleted", err)
return
}
}
func readFromLocalFile(files []string) *[]*types.KeyValue {
kva := []*types.KeyValue{}
for _, filepath := range files {
file, err := os.Open(filepath)
if err != nil {
fmt.Println(err)
}
dec := json.NewDecoder(file)
for {
var kv *types.KeyValue
if err = dec.Decode(&kv); err != nil {
break
}
kva = append(kva, kv)
}
_ = file.Close()
}
return &kva
}