Exercises
Put your MongoDB indexing skills to the test with questions covering essential index concepts and best practices. Explore the default _id index, compound index creation, geospatial indexes, partial indexes, and multikey indexes for array fields. You will also review how to list collection indexes, understand the benefits and trade-offs of indexing, and identify when an unused or costly index should be removed. This quiz is ideal for MongoDB developers, database administrators, and learners who want to improve query performance and design efficient collections.
Answer the questions below and check the explanation for each answer.
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In MongoDB, the default name for the primary index created on the _id field is _id_index. This index is automatically created to ensure the uniqueness of the _id field for each document within a collection.
To improve the performance of geospatial queries in MongoDB, you would create a 2dsphere Index. This index type is designed specifically to support queries that include geometry and geospatial data, such as location queries on Earth-like spheres. The 2dsphere index supports both precise calculations and queries based on the WGS84 datum.
A compound index on the fields userId in ascending order and createdAt in descending order can be created using { userId: 1, createdAt: -1 }. This specifies the order of the fields and the sort direction for each field.
Option 1 is true. In MongoDB, indexes can consume a significant amount of disk space depending on the number and size of the indexes created. Although they improve the speed of read operations, they require additional storage space.
Option 2 is false as indexes can impact the performance of write operations because they need to be updated when documents are inserted, updated, or deleted.
Option 3 is false because MongoDB allows for multiple indexes per collect
The db.collection.getIndexes() command is used to list all indexes in a MongoDB collection. It returns a list of documents that describe the indexes on the collection.
In MongoDB, you should consider removing an index when it is not used by any queries. Unused indexes can consume unnecessary storage space and potentially impact database performance negatively. This ensures that resources are not wasted maintaining indexes that do not contribute to improving query performance.
A partial index in MongoDB is an index that only includes documents that meet a specified filter expression. This helps to reduce the index size and improve query performance by excluding non-relevant documents.
A Multikey Index is specifically designed to handle array fields in documents. When you have documents with fields that contain arrays, MongoDB allows you to create a multikey index to efficiently index each element of the array. This improves query performance by enabling the database to quickly search for elements within arrays.
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