KeyTakeAways About MongoDB Multikey Indexes
- Multikey indexes in MongoDB are used to collect and sort data from fields containing array values, improving query performance for array fields.
- You are not allowed to specify a multikey index as the sherd key index.
- In MongoDB, hashed indexes are not multikey index.
- The multikey index cannot support the $expr operator.
- In MongoDB, if a filter query specifies the exact match for an array as a whole, then MongoDB scans the multikey index to look for the first element of the quarry array.
MongoDB Multikey Indexes
Indexes are special data structures that store some information related to the documents such that it becomes easy for MongoDB to find the right data file. They also store the value of a specific field or set of fields, ordered by the value of the field as specified in the index.
MongoDB allows indexing a field that holds an array value by creating an index key for each element in the array, such type of indexing is called Multikey Indexes.
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