11/6/2023 0 Comments Mongodb compass sort descending![]() FTS provides higher performance and greater flexibility to filter, rank, and sort through your database to quickly surface the most relevant results to your users. If you are running MongoDB in the Atlas service, consider using Atlas Full Text Search which provides a fully-managed Lucene index integrated with the MongoDB database. If you only want to match on a specific word in a field with a lot of text, then use a text index. ![]() Regular indexes are useful for matching the entire value of a field. Use text search to match words inside a field If your application’s query patterns are known in advance, then you should use more selective indexes on the specific fields accessed by the queries. You can define a filter that automatically indexes all matching fields, subdocuments, and arrays in a collection.Īs with any index, they also need to be stored and maintained, so they will add overhead to the database. Wildcard Indexes Are Not a Replacement for Workload-Based Index Planningįor workloads with many ad-hoc query patterns or that handle highly polymorphic document structures, wildcard indexes give you a lot of extra flexibility. MongoDB provides tooling to help you understand index usage, which we will cover later in this post. As fields are updated, associated indexes must be maintained, incurring additional CPU and disk I/O overhead. Indexes are resource-intensive: even with compression in the MongoDB WiredTiger storage engine, they consume RAM and disk. Compound indexes may include fields with low cardinality, but the value of the combined fields should exhibit high cardinality. Queries on fields with a small number of unique values (low cardinality) can return large result sets. Use Caution When Considering Indexes on Low-Cardinality Fields It is usually a good idea to do this anyway. This means covered queries are only possible when the shard key is part of the index. In sharded clusters, MongoDB internally needs to access the fields of the shard key. ![]() You need to explicitly exclude it from query results, or add it to the index. Read more in the documentation for explain results.Ī common gotcha when trying to achieve covered queries is that the _id field is always returned by default. If the explain() output displays totalDocsExamined as 0, this shows the query is covered by an index. To determine whether a query is a covered query, use the explain() method.
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