MongoDB Unhide Index

MongoDB Unhide Index

In MongoDB, the unhideIndex operation is used to unhide a previously hidden index in a collection. This method is essential for making hidden indexes available to the query planner again in MongoDB collections.

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Syntax

db.collection.unhideIndex(indexName)

The unhideIndex method takes an indexName parameter to specify the name of the index to unhide.

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Example MongoDB Unhide Index

Let's look at an example of how to use the unhideIndex method in the programGuru collection in MongoDB:

1. Unhide an Index

db.programGuru.unhideIndex("name_index")

This command unhides the index named name_index in the programGuru collection, making it available to the query planner again.

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Full Example

Let's go through a complete example that includes switching to a database, creating a collection, creating indexes, hiding an index, and then unhiding the index.

Step 1: Switch to a Database

This step involves switching to a database named myDatabase.

use myDatabase

In this example, we switch to the myDatabase database.

Step 2: Create a Collection

This step involves creating a new collection named programGuru in the myDatabase database.

db.createCollection("programGuru")

Here, we create a collection named programGuru.

Step 3: Insert Documents into the Collection

This step involves inserting documents into the programGuru collection.

db.programGuru.insertMany([
    { name: "John Doe", age: 30, email: "john.doe@example.com" },
    { name: "Jane Smith", age: 25, email: "jane.smith@example.com" },
    { name: "Jim Brown", age: 35, email: "jim.brown@example.com" }
])

We insert multiple documents into the programGuru collection.

Step 4: Create Indexes

This step involves creating indexes in the programGuru collection.

db.programGuru.createIndexes([
    { key: { name: 1 }, name: "name_index" },
    { key: { age: -1 }, name: "age_index" },
    { key: { email: 1 }, name: "email_index", unique: true }
])

We create three indexes: an ascending index on the name field, a descending index on the age field, and a unique index on the email field.

Step 5: Hide an Index

This step involves using the hideIndex method to hide an index from the query planner in the programGuru collection.

db.programGuru.hideIndex("name_index")

We hide the index named name_index from the query planner.

Step 6: Unhide the Index

This step involves using the unhideIndex method to unhide the previously hidden index.

db.programGuru.unhideIndex("name_index")

We unhide the index named name_index, making it available to the query planner again.

Conclusion

The MongoDB unhideIndex operation is crucial for making previously hidden indexes available to the query planner. Understanding how to use this method allows you to efficiently manage and optimize the performance of your MongoDB collections.