FAQ: MongoDB Search

Are there any charges for enabling and using MongoDB Search?

No, there are no additional fees or charges when you enable MongoDB Search on your cluster. However, you might observe an increase in resource utilization on the cluster depending on factors such as the size of the indexed collections or index definitions. To manage and control MongoDB Search resource utilization, you can deploy dedicated Search Nodes, which is an additive cost per node. We recommend this for your production environment.

Can I run partial string matching MongoDB Search queries?

Yes. The following MongoDB Search operators support partial string matching queries:

• autocomplete

• wildcard

• regex

Can I perform case-insensitive search with the wildcard or regex operator?

Yes. You can use the wildcard and regex operators with a custom analyzer to perform a case-insensitive search. You can define a custom analyzer with the following tokenizer and token filter to perform a wildcard case-insensitive search:

• keyword tokenizer

• lowercase token filter

Does storedSource support case-insensitive collation on fields?

Yes. The MongoDB Search storedSource option stores original values. To perform case-insensitive operations after the $search stage on the results returned using returnStoredSource option, you must set the default collation strength of your collection to 1 or 2 when you create it, and must not specify a different collation in your queries and indexes.

How do MongoDB Search indexes work on shards?

If you add shards to a collection with an existing MongoDB Search index, an initial sync occurs on the newly added shards for that MongoDB Search index. Each shard's MongoDB Search index contains only the documents from the collection that exists on that shard. To learn more, see Shard a Global Collection.

WARNING: If you shard a collection that already has a MongoDB Search index, you might experience a brief period of query downtime when the collection begins to appear on a shard. Also, if you add a shard for an already sharded collection that contains a MongoDB Search index, your search queries against that collection will fail until the initial sync process completes on the added shards. To learn more, see initial sync process.

Can I use the shard key to run MongoDB Search queries on specific shards?

No, you can't use the shard key to run MongoDB Search queries on a specific shard or a subset of shards. In a sharded cluster environment, MongoDB Search queries are scatter-gather queries that run on all the shards.

However, if you use zones to distribute a sharded collection over a subset of the shards in the cluster, MongoDB Search routes the query to the zone that contains the shards for the collection that you are querying and runs your $search queries on just the shards where the collection is located.

Do queries run on primary or secondary nodes?

By default, queries run on the primary node. You can configure your read preference or use replica set tags to specify read preference. To learn more, see What is MongoDB Search?.

Can I duplicate an index?

Yes, you can duplicate your index by performing the following:

Does MongoDB Search store my entire index in memory?

No, MongoDB Search uses memory for the JVM heap metrics, which stores the autocomplete and text tokens of your search index. Similar to other database engines, MongoDB Search stores the majority of the index files on the disk, which benefits from the underlying OS page cache.

Why is my search index disappearing?

• Verify that you entered the correct database and collection names. If you enter a non-existent database or collection name, the Atlas UI temporarily builds the index and deletes it shortly after.

• If you use the $out aggregation stage to overwrite your collection, you must delete and recreate your search index, as search indexes aren't copied to destination collections. To learn more, see $out Index Constraints.

• If you reshard a collection that uses MongoDB Search, this operation removes existing search indexes. Once the sharding operation completes, you must manually rebuild your collection's search index.

Can I restore MongoDB Search indexes from Cloud Backup snapshots?

For M10+ dedicated clusters, Atlas restores MongoDB Search index definitions from a Cloud Backup snapshot. Atlas doesn't restore search index data, so the mongot processes perform initial syncs for all restored search index definitions. If you've defined large search indexes on your cluster, you might experience delays during snapshot restorations.

Does MongoDB Search work with CSFLE encrypting clients?

Yes, you can use CSFLE encrypting clients to run MongoDB Search queries against non-encrypted data in MongoDB version 6.0 and later.

Can I query CSFLE encrypted data?

No, you can't query CSFLE encrypted data using MongoDB Search.

Can I use Queryable Encryption with MongoDB Search?

No, Queryable Encryption is incompatible with MongoDB Search.

Can I use MongoDB Search on time series collections?

No, you can't use MongoDB Search on time series collections.

Can I request new functionality?

Yes, use can request new functionality or upvote an existing request using the MongoDB Feedback Engine.

Can MongoDB Support access my Search infrastructure and logs?

Yes, MongoDB Support can access your MongoDB Search infrastructure on both dedicated and co-located nodes, as well as download mongot logs from these nodes. However, you can block access for MongoDB Support at the organization level and then grant access to MongoDB Support for 24 hours if needed. To learn more, see Configure MongoDB Support Access to Atlas Backend Infrastructure.

Can I run a $search query across multiple collections?

No, however, you can use $lookup and $unionWith to run a search query across multiple collections. To learn more, see How to Run MongoDB Search Queries Across Multiple Collections.