MongoDb解释失败:“未知顶级运算符:$ query" [英] MongoDb explain failed: "unknown top level operator: $query"

问题描述

我正试图从非常简单的查询中获得解释.它使用具有以下架构的帖子集合:

I'm trying to obtain explain from quite simple query. It uses posts collection with following schema:

> db.posts.findOne()
{
        "_id" : ObjectId("55236e6182bf196454a952b6"),
        "Content" : "wuOfCjKborHcxkoyXzXiW",
        "CreatedAtUtc" : ISODate("2014-01-18T23:59:30.023Z"),
        "Tags" : [
                "sjM",
                "Van",
                "Orm"
        ],
        "Title" : "msAQAbQwAl",
        "Author" : "yIIhato",
        "Comments" : [ ]
}

我要解释的查询是这样:

Query I want to explain is this:

db.posts.find( { $query: {}, $orderby: { "CreatedAtUtc" : -1 } } )

它产生正确的结果，没有任何错误.但是在我要解释时会引发异常.我已经尝试过以下命令来解释查询:

It produces proper result without any errors. But it throws the exception when I want to explain it. I've tried these commands to explain query:

db.posts.explain().find( { $query: {}, $orderby: { "CreatedAtUtc" : -1 } } )
db.posts.find( { $query: {}, $orderby: { "CreatedAtUtc" : -1 } } ).explain()

var cursor = db.posts.find( { $query: {}, $orderby: { "CreatedAtUtc" : -1 } } )
cursor.explain()

错误始终相同:

2015-11-08T16:20:40.137+0100 E QUERY    Error: explain failed: { "ok" : 0, "errm
sg" : "unknown top level operator: $query", "code" : 2 }
    at Error (<anonymous>)
    at Function.throwOrReturn (src/mongo/shell/explainable.js:34:19)
    at constructor.finish (src/mongo/shell/explain_query.js:188:36)
    at DBQuery.explain (src/mongo/shell/query.js:434:25)
    at (shell):1:8 at src/mongo/shell/explainable.js:34
>

推荐答案

来自 文档 :

From the docs:

请勿混用查询表格.如果您使用 $query 格式，请不要附加 将光标方法移至find().要修改查询，请使用元查询 运算符，例如 $explain .

Do not mix query forms. If you use the $query format, do not append cursor methods to the find(). To modify the query use the meta-query operators, such as $explain.

因此，以下两个操作是等效的:

Therefore, the following two operations are equivalent:

db.collection.find( { $query: { age : 25 }, $explain: true } )
db.collection.find( { age : 25 } ).explain()

因此，在您的情况下，作为 $explain 运算符自3.0版起已被弃用，请使用后一种查询形式，例如:

So in your case, as the $explain operator has been deprecated since version 3.0, use the latter form of querying like:

db.posts.find({}).sort({ "CreatedAtUtc" : -1 }).explain();

这篇关于MongoDb解释失败:“未知顶级运算符:$ query"的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！