Starting in MongoDB 4.2, you cannot run theexplaincommand/db.collection.explain()inexecutionStatsmode orallPlansExecutionmode for anaggregation pipelinethat contains the$outstage. Instead, you can either: run the explain inqueryPlannermode or
building完成之后,我们故意这一个这样的查询,针对quantity是一个范围,而type是一个定值的情况下,我们force mongodb去使用quantity开头 的复合索引,从而强制mongodb give up 那个以{type:1,quantity:1}的复合索引,很有意思哦,比如下图: 从图中,可以看到,我们检查了6个keys,而从最终找到了2个文档,现在我们就知道...
If you are familiar with the EXPLAIN command in MySQL, the goals of MongoDB’s explain() method are exactly the same. Explainable object You can apply the explain() method to a query or a cursor in the following way, as per any other method: 1 MongoDB > db.mycollection.find()....
command, which details the command being explained. queryPlanner, which details the plan selected by thequery optimizerand lists the rejected plans. executionStats, which details the execution of the winning plan and the rejected plans. serverInfo, which provides information on the MongoDB instance....
在MongoDB,这种计数采取的数量级的时间比你希望的要长。有一个open ticke,目前为2.4,在这里,我希望希望他们可以将它弄出来。在那之前,你可以留下自己的数据汇总。在插入一个新的文档的时候,你可以在mongo中用$inccommand存储数据汇总。 副本集读取不一致 ...
The explain() command provides a lot of information. If you are familiar with MySQL, then you probably know about the command EXPLAIN. In MongoDB, we have a similar feature, and the goal of using it is exactly the same: find out how we can improve a query in order to reduce the ...
db.collection.explain().find()该方法与db.collection.find().explain()类似,但是存在以下关键差异 The db.collection.explain()method wraps the explain command and is the preferred way to run explain.db.collection.explain().find()is similar to db.collection.find().explain()withthe following key di...
db.collection.count({username:"my_username"}); 1. 在MongoDB,这种计数采取的数量级的时间比你希望的要长。有一个open ticke,目前为2.4,在这里,我希望希望他们可以将它弄出来。在那之前,你可以留下自己的数据汇总。在插入一个新的文档的时候,你可以在mongo中用$inccommand ...
Thedb.collection.explain()method wraps theexplaincommand and is the preferred way to runexplain. db.collection.explain().find()is similar todb.collection.find().explain()with the following key differences: Thedb.collection.explain().find()construct allows for the additional chaining of query modif...
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