wukong引擎源码分析之索引——part 3 文档评分 无非就是将docid对应的fields信息存储起来，为搜索结果rank评分用

之前的文章分析过，接受索引请求处理的代码在segmenter_worker.go里：

func (engine *Engine) segmenterWorker() {
    for {
        request := <-engine.segmenterChannel //关键

        tokensMap := make(map[string][]int)
        numTokens := 0
        if !engine.initOptions.NotUsingSegmenter && request.data.Content != "" {
            // 当文档正文不为空时，优先从内容分词中得到关键词
            segments := engine.segmenter.Segment([]byte(request.data.Content))
            for _, segment := range segments {
                token := segment.Token().Text()
                if !engine.stopTokens.IsStopToken(token) {
                    tokensMap[token] = append(tokensMap[token], segment.Start())
                }
            }
            numTokens = len(segments)
        } else {
            // 否则载入用户输入的关键词
            for _, t := range request.data.Tokens {
                if !engine.stopTokens.IsStopToken(t.Text) {
                    tokensMap[t.Text] = t.Locations
                }
            }
            numTokens = len(request.data.Tokens)
        }

        // 加入非分词的文档标签
        for _, label := range request.data.Labels {
            if !engine.initOptions.NotUsingSegmenter {
                if !engine.stopTokens.IsStopToken(label) {
                    tokensMap[label] = []int{}
                }
            } else {
                tokensMap[label] = []int{}
            }
        }

        indexerRequest := indexerAddDocumentRequest{
            document: &types.DocumentIndex{
                DocId:       request.docId,
                TokenLength: float32(numTokens),
                Keywords:    make([]types.KeywordIndex, len(tokensMap)),
            },
        }
        iTokens := 0
        for k, v := range tokensMap {
            indexerRequest.document.Keywords[iTokens] = types.KeywordIndex{
                Text: k,
                // 非分词标注的词频设置为0，不参与tf-idf计算
                Frequency: float32(len(v)),
                Starts:    v}
            iTokens++
        }

        var dealDocInfoChan = make(chan bool, 1)

        indexerRequest.dealDocInfoChan = dealDocInfoChan
        engine.indexerAddDocumentChannels[request.shard] <- indexerRequest

        rankerRequest := rankerAddDocRequest{
            docId:           request.docId,
            fields:          request.data.Fields,
            dealDocInfoChan: dealDocInfoChan,
        }
        engine.rankerAddDocChannels[request.shard] <- rankerRequest
    }
}

上面代码的作用就是在统计词频和单词位置（注意：tag也是作为搜索的单词，不过其词频是0，而无法参与tf-idf计算），并封装为indexerRequest，发送给engine.indexerAddDocumentChannels[request.shard]

此外，红色部分代码是在为文档评分做准备，engine/ranker_worker.go：

func (engine *Engine) rankerAddDocWorker(shard int) {
    for {
        request := <-engine.rankerAddDocChannels[shard] //关键
        docInfo := engine.rankers[shard].AddDoc(request.docId, request.fields, request.dealDocInfoChan)
        // save
        if engine.initOptions.UsePersistentStorage {
            engine.persistentStorageIndexDocumentChannels[shard] <- persistentStorageIndexDocumentRequest{
                typ:     "info",
                docId:   request.docId,
                docInfo: docInfo,
            }
        }
    }
}

AddDoc无非就是将docid对应的fields信息存储起来，为搜索结果rank评分用！

// 给某个文档添加评分字段
func (ranker *Ranker) AddDoc(docId uint64, fields interface{}, dealDocInfoChan <-chan bool) *types.DocInfo {
    if ranker.initialized == false {
        log.Fatal("排序器尚未初始化")
    }

    <-dealDocInfoChan // 等待索引器处理完成

    ranker.DocInfosShard.Lock()
    defer ranker.DocInfosShard.Unlock()
    if _, found := ranker.DocInfosShard.DocInfos[docId]; !found {
        ranker.DocInfosShard.DocInfos[docId] = new(types.DocInfo)
        ranker.DocInfosShard.NumDocuments++
    }
    ranker.DocInfosShard.DocInfos[docId].Fields = fields
    return ranker.DocInfosShard.DocInfos[docId]
}