Golang操作elasticsearch

• 使用第三方包：olivere github。总结一下olivere操作ES的常用功能，方便查阅。
• 说明：以下例子用到的es index:”test”, es type:”test”, es address: “http://10.1.1.1:9200”

1. 新建es client

   func ESClient() (client *elastic.Client,err error){
       file := "./log.log"
       logFile, _ := os.OpenFile(file, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0766) // 应该判断error，此处简略
       cfg := []elastic.ClientOptionFunc{
           elastic.SetURL("http://10.1.1.1:9200"),
           elastic.SetSniff(false),
           elastic.SetInfoLog(log.New(logFile, "ES-INFO: ", 0)),
           elastic.SetTraceLog(log.New(logFile, "ES-TRACE: ", 0)),
           elastic.SetErrorLog(log.New(logFile, "ES-ERROR: ", 0)),
       }
       client,err =elastic.NewClient(cfg ...)
       return
   }

2. 查看某文档是否存在,给定文档ID查询

   func isExists(id string)bool{
       client,_ := ESClient()
       defer client.Stop()
       exist,_ := client.Exists().Index("test").Type("test").Id(id).Do(context.Background())
       if !exist{
           log.Println("ID may be incorrect! ",id)
           return false
       }
       return true
   }

3. 获取某文档的内容

   func(doc *myDocument) Get(id string){
       client ,_:= ESClient()
       defer client.Stop() 
       if !isExists(id){
           return
       }
       esResponse,err := client.Get().Index("test").Type("test").Id(id).Do(context.Background())
       if err != nil {
           // Handle Error
           return
       }
       json.Unmarshal(*esResponse.Source,&doc)
   }

4. 新增文档

   func(doc *myDocument) Add(id string){
       client ,_:= ESClient()
       defer client.Stop() 
       if !isExists(id){
           return
       }
       client.Index().Index("test").Type("test").Id(id).BodyJson(doc).Do(context.Background())
   }

5. 批量新增

   func BulkAdd(docs []myDocument){
       bulkRequest := seriesClient.Bulk()
       client ,_:= ESClient()
       defer client.Stop()
       for _,doc := range docs{
           esRequest := elastic.NewBulkIndexRequest().Index("test").Type("test").Id(id).Doc(doc)
           bulkRequest = bulkRequest.Add(esRequest)
       }
       bulkRequest.Do(context.Background())
   }

6. 更新文档

   func Update(updateField *map[string]interface{},id string){
       client ,_:= ESClient()
       defer client.Stop()
       if !isExists(id){
           return
       }
       _,err:=client.Update().Index("test").Type("test").Id(id).Doc(updateField).Do(context.Background())
       if err != nil{
           //Handle Error
       }
   }

7. 删除文档

   func Delete(id string){
       client ,_:= ESClient()
       defer client.Stop()
       if !isExists(id){
           return
       }
       _,err:=client.Delete().Index("test").Type("test").Id(id).Do(context.Background())
       if err != nil{
           //Handle Error
       }
   }

8. 搜索文档（搜索是ES非常引以为傲的功能，以下示例是相对复杂的查询条件，需将查询结果排序，按页返回）

   func Search(criteria *SearchCriteria)(docs []myDocument){
       client ,_:= ESClient()
       defer client.Stop()
       query := elastic.NewBoolQuery()
       query = query.Must(elastic.NewTermQuery("category",criteria.Category))
       query=query.Must(elastic.NewMatchQuery("title",criteria.Title))
       query=query.Must(elastic.NewRangeQuery("update_timestamp").Gte(criteria.UpdateTime))
       esResponse,_ :=client.Search().Index("test").Type("test").
           Query(query).Sort(criteria.Sort,criteria.Order=="ASC"||criteria.Order=="asc").
           From(criteria.Offset).Size(criteria.Limit).Do(context.Background())
       for _,value:= range esResponse.Hits.Hits{
           var doc *myDocument
           json.Unmarshal(*value.Source,&doc)
           docs = append(docs,doc)
       }
       return
   }
   
   type SearchCriteria struct{
       Category string `json:"category"`
       Limit int `json:"limit"`
       Offset int `json:"offset"`
       Title string `json:"title"`
       UpdateTime int64 `json:"update_timestamp"`
       Order string `json:"order"`
       Sort string `json:"sort"`
   }