php小编草莓在这里为大家介绍一种常见的需求：如何从MongoDB文档中获取元素并使用Go Mongo驱动程序更新其值。MongoDB是一种流行的NoSQL数据库，而Go是一种强大的编程语言，两者的结合可以带来很多好处。在本文中，我们将探讨如何使用Go Mongo驱动程序来实现这个需求，帮助您更好地理解和应用这个技术。
问题内容
嘿，我正在使用 go.mongodb.org/mongo-driver 包来使用 golang。这是我的代码：
package src
import (
"context"
"fmt"
"log"
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
)
var (
client *mongo.client
stickerscol *mongo.collection
)
func init() {
log.println("setting up database...")
var err error
client, err = mongo.connect(context.background(), options.client().applyuri(envars.dburl))
if err != nil {
log.fatal(err)
}
log.println("connected to database")
stickerscol = client.database("stickersbot").collection("stickers")
chatcol = client.database("stickersbot").collection("chat")
}
func changedefaultpack(userid int64, stickername string, format string) error {
fmt.println(userid, stickername, format)
filter := bson.m{
"_id": userid,
"stickers.stickername": stickername,
"stickers.stickerpacktype": format,
}
updateother := bson.m{
"$set": bson.m{
"stickers.$[elem].isdefault": false,
},
}
update := bson.m{
"$set": bson.m{
"stickers.$.isdefault": true,
},
}
arrayfilters := options.arrayfilters{
filters: []interface{}{bson.m{"elem.stickerpacktype": format}},
}
updateoptions := options.update().setarrayfilters(arrayfilters)
_, err := stickerscol.updatemany(context.todo(), filter, updateother, updateoptions)
if err != nil {
return err
}
ok, err := stickerscol.updateone(context.background(), filter, update, options.update().setupsert(true))
if err != nil {
return err
}
if ok.modifiedcount == 0 {
fmt.println("no document matched")
return fmt.errorf("no document matched")
}
return err
}
这是数据库结构：
...
{
"_id": 1633375527,
"stickers": [
{
"stickerpacktype": "static",
"stickername": "gVtOy_1633375527_by_ChadManBot",
"isdefault": true
},
{
"stickerpacktype": "animated",
"stickername": "zIjsa_1633375527_by_ChadManBot",
"isdefault": true
},
{
"stickerpacktype": "video",
"stickername": "bJBle_1633375527_by_ChadManBot",
"isdefault": true
},
{
"stickerpacktype": "static",
"stickername": "iujiw_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "video",
"stickername": "CHnqb_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "XKJUP_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "animated",
"stickername": "pCFlC_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "animated",
"stickername": "jGGgt_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "animated",
"stickername": "cTxyA_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "animated",
"stickername": "ZfYXO_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "xJUkA_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "HIvsY_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "WIHFQ_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "OqjtE_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "QNysO_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "OrTsT_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "FzROg_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "QUBcT_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "NsZfM_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "AkxVM_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "Ddvus_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "LXfHV_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "sTaMv_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "vppgK_1633375527_by_ChadManBot",
"isdefault": false
}
],
"stickerpackcount": 2
}
...
我需要我的代码是找到与给定 id 和贴纸类型匹配的贴纸包列表，并将其默认值设置为 false 并将传递给 func 的包的默认值设置为 true。
基本上只是将其中一个设置为默认值，将其他设置为非默认值。有人可以解释一下为什么这个函数返回未找到文档吗？
解决方法
当有多个字段匹配时，您应该使用 $elemmatch 运算符。否则，$ 运算符不起作用。请参阅 使用多个字段匹配更新嵌入文档。
并且您不需要 updatemany 来更新单个文档中的多个数组元素。请改用 updateone。
这是基于您的代码和数据的演示：
package main
import (
"context"
"fmt"
"log"
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
)
var (
client *mongo.client
stickerscol *mongo.collection
)
func init() {
log.println("setting up database...")
var err error
client, err = mongo.connect(context.background(), options.client().applyuri("mongodb://localhost"))
if err != nil {
log.fatal(err)
}
log.println("connected to database")
stickerscol = client.database("stickersbot").collection("stickers")
}
func changedefaultpack(userid int64, stickername string, format string) error {
fmt.println(userid, stickername, format)
filter := bson.m{
"_id": userid,
"stickers": bson.m{
"$elemmatch": bson.m{
"stickername": stickername,
"stickerpacktype": format,
},
},
}
updateother := bson.m{
"$set": bson.m{
"stickers.$[elem].isdefault": false,
},
}
arrayfilters := options.arrayfilters{
filters: []interface{}{bson.m{"elem.stickerpacktype": format}},
}
updateoptions := options.update().setarrayfilters(arrayfilters)
result, err := stickerscol.updateone(context.background(), filter, updateother, updateoptions)
if err != nil {
return err
}
log.printf("update other: %+v\n", result)
update := bson.m{
"$set": bson.m{
"stickers.$.isdefault": true,
},
}
ok, err := stickerscol.updateone(context.background(), filter, update, options.update().setupsert(true))
if err != nil {
return err
}
log.printf("update default: %+v\n", ok)
if ok.modifiedcount == 0 {
fmt.println("no document matched")
return fmt.errorf("no document matched")
}
return err
}
func main() {
if err := changedefaultpack(1633375527, "ddvus_1633375527_by_chadmanbot", "static"); err != nil {
panic(err)
}
}
运行演示，您将观察到文档发生以下更改：
--- before.json 2023-06-27 00:34:32.721978745 +0800
after.json 2023-06-27 00:34:59.489836137 +0800
@@ -4,7 +4,7 @@
{
"stickerpacktype": "static",
"stickername": "gVtOy_1633375527_by_ChadManBot",
- "isdefault": true
+ "isdefault": false
},
{
"stickerpacktype": "animated",
@@ -104,7 +104,7 @@
{
"stickerpacktype": "static",
"stickername": "Ddvus_1633375527_by_ChadManBot",
- "isdefault": false
+ "isdefault": true
},
{
"stickerpacktype": "static", 
