Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Select a document in MongoDB
Answer:
To select (find) a document in MongoDB, you can use the following syntax in the mongodb Interactive shell.
use my_db
db.users.find({name:"peter"})You need to switch to the current database (e.g. my_db) and then execute your select statement.
Explain query execution plan in MongoDB
Answer:
Like MySQL, you can get a better understanding of the performance of your MongoDB's query, you can use the $explain feature.
E.g.
db.collection.find(query).explain();Repair and compact database in MongoDB
Answer:
To repair and compact a database in MongoDB, you can use the following command in the mongodb Interactive shell.
1. Select the database
use test
2. Repair the current database
db.repairDatabase()
Done.
Count the total number of objects in the collection in MongoDB
Answer:
In MongoDB, to count the total number of objects in the collection, you can use the following statement in the mongodb Interactive shell.
db.test.count()
The above statement will return the total number of objects in the collection "test"
Creates an index in MongoDB
Answer:
In an given collection, if you want to add an index on a specify field, you can do the following in the mongodb Interactive shell.
db.test.ensureIndex( { name : 1 } )
The key "name" from now on will have index enabled.
