如何使用 mgo 创建(或确保)散列索引包?
我需要一个与此等效的 go 代码:
>> db.collection.createIndex( { _id: "hashed" } )
我尝试过使用 runCommand,但只有 createIndexes
命令需要索引规范
列表。我不知道那是什么以及如何创建索引规范
。
最佳答案
您可以按照 Collection.EnsureIndex
中的说明进行操作:
Other kinds of indexes are also supported through that API. Here is an example:
index := Index{
Key: []string{"$2d:loc"},
Bits: 26,
}
err := collection.EnsureIndex(index)
The example above requests the creation of a "2d" index for the "loc" field.
基本上,您的格式为 $<indexType>:<indexedField>
,如下图:
package main
import mgo "gopkg.in/mgo.v2"
const (
db = "so_hashed_idx"
coll = "testcoll"
)
func main() {
var s *mgo.Session
var err error
if s, err = mgo.Dial("127.0.0.1:27017"); err != nil {
panic(err)
}
// An index spec is nothing more than a fancy word for the keys
// or the key/value pairs handed over to the Key slice of the
// Index type.
idx := mgo.Index{
Key: []string{"$hashed:_id"},
}
if err := s.DB(db).C(coll).EnsureIndex(idx); err != nil {
panic(err)
}
}
构建并运行上述结果为 so_hashed_idx.testcoll
显示其索引如下
> db.testcoll.getIndices()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "so_hashed_idx.testcoll"
},
{
"v" : 1,
"key" : {
"_id" : "hashed"
},
"name" : "_id_hashed",
"ns" : "so_hashed_idx.testcoll"
}
]
关于mongodb - 如何通过 mgo (golang) 创建哈希索引,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45389410/