Multikey Indexes

Overview

Multikey indexes are indexes that improve the performance of queries on array-valued fields. You can create a multikey index on a collection by using the MongoDB\Collection::createIndex() method and the same syntax that you use to create single field or compound indexes.

Create a Multikey Index

Use the MongoDB\Collection::createIndex() method to create a multikey index. The following example creates an index in ascending order on the array-valued cast field:

$indexName = $collection->createIndex(['cast' => 1]);

The following is an example of a query that is covered by the index created in the preceding code example:

$document = $collection->findOne(
    ['cast' => ['$in' => ['Aamir Khan', 'Kajol']]]
);
echo json_encode($document), PHP_EOL;

{"_id":...,"title":"Holi",...,"cast":["Ashutosh Gowariker",
"Aamir Khan","Rahul Ranade","Sanjeev Gandhi"],...}

Additional Information

Multikey indexes behave differently from other indexes in terms of query coverage, index bound computation, and sort behavior. To learn more about the behavior and limitations of multikey indexes, see Multikey Indexes in the MongoDB Server manual.

To view runnable examples that demonstrate how to manage indexes, see Optimize Queries by Using Indexes.