12. Indexing in MongoDB

Indexing is a crucial feature of MongoDB that enables efficient query execution. Without indexes, MongoDB must perform a full scan of each document in a collection to select the documents that match the query. With indexes, MongoDB can limit the search to documents that match the index. This can significantly improve query performance.

Indices are special data structures that store a small portion of the data in the database dataset. This data is stored in an easy-to-swipe manner. Indexes store the value of a specific field or set of fields, ordered by the field values. Index ordering allows MongoDB to support sort queries and help limit the amount of data read during the query.

Indices in MongoDB are similar to indexes in other database systems. MongoDB defines indexes at a per-collection level and can create indexes on any field or subfield of documents in a MongoDB collection.

Types of indexes in MongoDB

MongoDB provides several types of indexes that support different types of data queries. Let's discuss the most common types of indexes in MongoDB.

Single Index

Unique indexes reject documents whose value in the indexed field or fields is a duplicate. A unique index ensures that the indexed field or set of fields contains only unique values. For example, you may want to ensure that no customer can register twice with the same email address.

Composite Index

MongoDB also supports composite indexes, where a single index structure refers to multiple fields within a document collection. Composite indexes can support queries that match multiple fields.

Text index

Text indexes can include any field whose value is a string or an array of strings. They are designed to improve the performance of text queries.

2dsphere index

2dsphere indexes support queries that calculate geometries on a two-dimensional sphere. 2dsphere indexes are used to store geospatial data such as geographic locations.

Creating indexes in MongoDB

To create an index in MongoDB, we use the createIndex() method. This method creates a new index on a collection if the index does not exist; otherwise, the method has no effect.

Index maintenance

Indices are fundamental to database performance, but they also have costs. They consume disk space and can affect database write performance. Therefore, it is important to ensure that indexes are designed effectively and maintained correctly.

It is crucial to monitor index usage and remove any indexes that are not being used. MongoDB provides tools for monitoring index usage. In addition, MongoDB also provides index maintenance operations, such as reindexing all indexes in a collection, which can be useful in improving index performance.

In summary, indexing is a powerful feature of MongoDB that allows efficient query execution. It is essential to understand how to create and maintain indexes to ensure optimal database performance.

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