Without an index MongoDB scans every document. An index lets it find matches quickly.
db.students.createIndex({ city: 1 })- Unique:
createIndex({ email: 1 }, { unique: true }) getIndexes()lists them;.explain()shows how a query runs.
MongoDB Indexes
Make queries fast.
✍️ 2 exercises in this lessonKey Takeaways: MongoDB Indexes
Mastering MongoDB Indexes helps you write clean and reliable MongoDB code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.
MongoDB Indexes Code Example
MongoDBdb.students.createIndex({ city: 1 })
db.students.createIndex({ email: 1 }, { unique: true })
db.students.getIndexes()Output
city_1
email_1
[ { v: 2, key: { _id: 1 }, name: '_id_' }, { v: 2, key: { city: 1 }, name: 'city_1' }, { v: 2, key: { email: 1 }, name: 'email_1', unique: true } ]
Run this example on your own computer. The "Get Started" lesson shows how to set it up.
MongoDB Indexes Practice Exercises
Check what you learned in “MongoDB Indexes”.
/ 2 solved
Fill in the blank
Create an index on the email field.
db.users.({ email: 1 })
✓ Correct!
Not quite. Try again.
Multiple choice
What is the downside of too many indexes?
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