英文:
Is there a way that can find one document and clone it with changing id/value in mongodb with Go
问题
假设我有以下代码：
var result bson.M
err := coll.FindOne(context.TODO(), filter).Decode(&result)
if err != nil {
panic(err)
}
// somehow I can change the _id before I do insertOne
if _, err := coll.InsertOne(context.TODO(), result); err != nil {
panic(err)
}
有没有办法在不知道数据结构的情况下进行insertOne操作？但是在插入之前我必须更改_id。
英文:
suppose I have code like this:
var result bson.M
err := coll.FindOne(context.TODO(), filter).Decode(&result)
if err != nil {
panic(err)
}
// somehow I can change the _id before I do insertOne
if _, err := coll.InsertOne(context.TODO(), result); err != nil {
panic(err)
}
is there a way I can insertOne without knowing the data struct? But I have to change the _id before I insert it.
答案1
得分: 0
在MongoDB中，ID字段始终为_id，因此您可以简单地执行以下操作：
result["_id"] = ... // 分配新的ID值
另请注意，bson.M是一个映射，因此不保留顺序。您可以仅更改ID并插入克隆，但字段顺序可能会改变。这通常不是一个问题。
如果顺序也很重要，请改用bson.D而不是bson.M，它保留顺序，但查找_id会更复杂：您必须使用循环，因为bson.D不是映射而是切片。
使用bson.D时，代码可能如下所示：
var result bson.D
// 查询...
// 更改ID：
for i := range result {
if result[i].Key == "_id" {
result[i].Value = ... // 新的ID值
break
}
}
// 现在您可以插入result
英文:
The ID field in MongoDB is always _id, so you may simply do:
result["_id"] = ... // Assign new ID value
Also please note that bson.M is a map, and as such does not retain order. You may simply change only the ID and insert the clone, but field order may change. This usually isn't a problem.
If order is also important, use bson.D instead of bson.M which retains order, but finding the _id is a little more complex: you have to use a loop as bson.D is not a map but a slice.
This is how it could look like when using bson.D:
var result bson.D
// Query...
// Change ID:
for i := range result {
if result[i].Key == "_id" {
result[i].Value = ... // new id value
break
}
}
// Now you can insert result
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