Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Understanding MongoDB Query Plan
To get a query plan in MongoDB, use explain(). The $explain operator gives information on the query plan.
Let us create a collection with documents −
> db.demo408.insertOne({"Value":50});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e70e3a115dc524f70227678")
}
> db.demo408.insertOne({"Value":20});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e70e3a715dc524f70227679")
}
> db.demo408.insertOne({"Value":45});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e70e3ac15dc524f7022767a")
}
> db.demo408.insertOne({"Value":35});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e70e3af15dc524f7022767b")
}
> db.demo408.createIndex({Value:1});
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}Display all documents from a collection with the help of find() method −
> db.demo408.find();
This will produce the following output −
{ "_id" : ObjectId("5e70e3a115dc524f70227678"), "Value" : 50 }
{ "_id" : ObjectId("5e70e3a715dc524f70227679"), "Value" : 20 }
{ "_id" : ObjectId("5e70e3ac15dc524f7022767a"), "Value" : 45 }
{ "_id" : ObjectId("5e70e3af15dc524f7022767b"), "Value" : 35 }Following is the query to understand query plan in MongoDB −
> db.demo408.explain().find( { Value: { $gt: 40 } } );This will produce the following output −
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "test.demo408",
"indexFilterSet" : false,
"parsedQuery" : {
"Value" : {
"$gt" : 40
}
},
"winningPlan" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"Value" : 1
},
"indexName" : "Value_1",
"isMultiKey" : false,
"multiKeyPaths" : {
"Value" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"Value" : [
"(40.0, inf.0]"
]
}
}
},
"rejectedPlans" : [ ]
},
"serverInfo" : {
"host" : "DESKTOP-QN2RB3H",
"port" : 27017,
"version" : "4.0.5",
"gitVersion" : "3739429dd92b92d1b0ab120911a23d50bf03c412"
},
"ok" : 1
}
Updated on: 03-Apr-2020
404 Views
Advertisements