1. 操作ElasticSearch
1.1.1. elastic client
我们使用第三方库https://github.com/olivere/elastic 来连接ES并进行操作。
注意下载与你的ES相同版本的client，例如我们这里使用的ES是7.2.1的版本，那么我们下载的client也要与之对应为github.com/olivere/elastic/v7。
使用go.mod来管理依赖：
require (
github.com/olivere/elastic/v7 v7.0.4
)
简单示例：
package main
import (
"context"
"fmt"
"github.com/olivere/elastic/v7"
)
// Elasticsearch demo
type Person struct {
Name string `json:"name"`
Age int `json:"age"`
Married bool `json:"married"`
}
func main() {
client, err := elastic.NewClient(elastic.SetURL("http://127.0.0.1:9200"))
if err != nil {
// Handle error
panic(err)
}
fmt.Println("connect to es success")
p1 := Person{Name: "lmh", Age: 18, Married: false}
put1, err := client.Index().
Index("user").
BodyJson(p1).
Do(context.Background())
if err != nil {
// Handle error
panic(err)
}
fmt.Printf("Indexed user %s to index %s, type %s\n", put1.Id, put1.Index, put1.Type)
}
示例2：
package main
import (
"context"
"fmt"
"log"
"os"
"reflect"
"gopkg.in/olivere/elastic.v7" //这里使用的是版本5，最新的是6，有改动
)
var client *elastic.Client
var host = "http://127.0.0.1:9200/"
type Employee struct {
FirstName string `json:"first_name"`
LastName string `json:"last_name"`
Age int `json:"age"`
About string `json:"about"`
Interests []string `json:"interests"`
}
//初始化
func init() {
errorlog := log.New(os.Stdout, "APP", log.LstdFlags)
var err error
client, err = elastic.NewClient(elastic.SetErrorLog(errorlog), elastic.SetURL(host))
if err != nil {
panic(err)
}
info, code, err := client.Ping(host).Do(context.Background())
if err != nil {
panic(err)
}
fmt.Printf("Elasticsearch returned with code %d and version %s\n", code, info.Version.Number)
esversion, err := client.ElasticsearchVersion(host)
if err != nil {
panic(err)
}
fmt.Printf("Elasticsearch version %s\n", esversion)
}
/*下面是简单的CURD*/
//创建
func create() {
//使用结构体
e1 := Employee{"Jane", "Smith", 32, "I like to collect rock albums", []string{"music"}}
put1, err := client.Index().
Index("megacorp").
Type("employee").
Id("1").
BodyJson(e1).
Do(context.Background())
if err != nil {
panic(err)
}
fmt.Printf("Indexed tweet %s to index s%s, type %s\n", put1.Id, put1.Index, put1.Type)
//使用字符串
e2 := `{"first_name":"John","last_name":"Smith","age":25,"about":"I love to go rock climbing","interests":["sports","music"]}`
put2, err := client.Index().
Index("megacorp").
Type("employee").
Id("2").
BodyJson(e2).
Do(context.Background())
if err != nil {
panic(err)
}
fmt.Printf("Indexed tweet %s to index s%s, type %s\n", put2.Id, put2.Index, put2.Type)
e3 := `{"first_name":"Douglas","last_name":"Fir","age":35,"about":"I like to build cabinets","interests":["forestry"]}`
put3, err := client.Index().
Index("megacorp").
Type("employee").
Id("3").
BodyJson(e3).
Do(context.Background())
if err != nil {
panic(err)
}
fmt.Printf("Indexed tweet %s to index s%s, type %s\n", put3.Id, put3.Index, put3.Type)
}
//删除
func delete() {
res, err := client.Delete().Index("megacorp").
Type("employee").
Id("1").
Do(context.Background())
if err != nil {
println(err.Error())
return
}
fmt.Printf("delete result %s\n", res.Result)
}
//修改
func update() {
res, err := client.Update().
Index("megacorp").
Type("employee").
Id("2").
Doc(map[string]interface{}{"age": 88}).
Do(context.Background())
if err != nil {
println(err.Error())
}
fmt.Printf("update age %s\n", res.Result)
}
//查找
func gets() {
//通过id查找
get1, err := client.Get().Index("megacorp").Type("employee").Id("2").Do(context.Background())
if err != nil {
panic(err)
}
if get1.Found {
fmt.Printf("Got document %s in version %d from index %s, type %s\n", get1.Id, get1.Version, get1.Index, get1.Type)
}
}
//搜索
func query() {
var res *elastic.SearchResult
var err error
//取所有
res, err = client.Search("megacorp").Type("employee").Do(context.Background())
printEmployee(res, err)
//字段相等
q := elastic.NewQueryStringQuery("last_name:Smith")
res, err = client.Search("megacorp").Type("employee").Query(q).Do(context.Background())
if err != nil {
println(err.Error())
}
printEmployee(res, err)
//条件查询
//年龄大于30岁的
boolQ := elastic.NewBoolQuery()
boolQ.Must(elastic.NewMatchQuery("last_name", "smith"))
boolQ.Filter(elastic.NewRangeQuery("age").Gt(30))
res, err = client.Search("megacorp").Type("employee").Query(q).Do(context.Background())
printEmployee(res, err)
//短语搜索 搜索about字段中有 rock climbing
matchPhraseQuery := elastic.NewMatchPhraseQuery("about", "rock climbing")
res, err = client.Search("megacorp").Type("employee").Query(matchPhraseQuery).Do(context.Background())
printEmployee(res, err)
//分析 interests
aggs := elastic.NewTermsAggregation().Field("interests")
res, err = client.Search("megacorp").Type("employee").Aggregation("all_interests", aggs).Do(context.Background())
printEmployee(res, err)
}
//简单分页
func list(size, page int) {
if size < 0 || page < 1 {
fmt.Printf("param error")
return
}
res, err := client.Search("megacorp").
Type("employee").
Size(size).
From((page - 1) * size).
Do(context.Background())
printEmployee(res, err)
}
//打印查询到的Employee
func printEmployee(res *elastic.SearchResult, err error) {
if err != nil {
print(err.Error())
return
}
var typ Employee
for _, item := range res.Each(reflect.TypeOf(typ)) { //从搜索结果中取数据的方法
t := item.(Employee)
fmt.Printf("%#v\n", t)
}
}
func main() {
create()
delete()
update()
gets()
query()
list(1, 3)
}