如何改善MongoDB中的查询字段？
为了改善MongoDB中的查询字段，您需要使用索引。让我们创建包含文档的集合
> db.improveQueryDemo.insertOne(
... {
... "PlayerDetails":[
... {"PlayerName": "John", "PlayerGameScore": 5690},
... {"PlayerName": "Carol", "PlayerGameScore": 2690},
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9dbaf875e2eeda1d5c3670")
}以下是在find()方法的帮助下显示集合中所有文档的查询
> db.improveQueryDemo.find().pretty();
这将产生以下输出
{
"_id" : ObjectId("5c9dbaf875e2eeda1d5c3670"),
"PlayerDetails" : [
{
"PlayerName" : "John",
"PlayerGameScore" : 5690
},
{
"PlayerName" : "Carol",
"PlayerGameScore" : 2690
}
]
}现在，您需要在字段上创建索引以改善查询。以下是查询
> db.improveQueryDemo.ensureIndex({"PlayerDetails.PlayerName":1});这将产生以下输出
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}现在，您可以按完全匹配进行搜索。以下是查询
> db.improveQueryDemo.find({"PlayerDetails.PlayerName":"Carol"}).pretty();这将产生以下输出
{
"_id" : ObjectId("5c9dbaf875e2eeda1d5c3670"),
"PlayerDetails" : [
{
"PlayerName" : "John",
"PlayerGameScore" : 5690
},
{
"PlayerName" : "Carol",
"PlayerGameScore" : 2690
}
]
}