In MongoDB, the dropIndexes() method allows you to drop one or more indexes from a collection.
To drop a single index, pass the name of the index or its definition/specification document. If it’s a text index, you can only specify the index name.
To drop multiple indexes, pass the index names in an array.
To drop all indexes (except for the _id index), don’t pass any arguments.
There are several ways to drop an index in MongoDB, one of which is to use the dropIndex() method.
It’s pretty simple to use – just pass the name of the index or its definition/specification document. If it’s a text index, you can only specify the index name.
In MongoDB, you can use the getIndexes() method to get a list of indexes on a collection.
You can also loop through each collection in a database to return all indexes in the database.
In MongoDB, the db.collection.unhideIndex() method unhides a hidden index.
A hidden index is one that’s hidden from the query planner. When you unhide an index, it is no longer hidden from the query planner, and it’s immediately available for use.
MongoDB introduced the db.collection.hideIndex() method in MongoDB 4.4.
This method hides an existing index from the query planner. This allows you to evaluate the potential impact of dropping an index without actually dropping the index.
If hiding it has a negative impact, you can use db.collection.unhideIndex() to unhide the index. This saves you from having to drop the index, then recreate it.
In MongoDB, you can create an index on a collection using the createIndex() method, the createIndexes() method, or the createIndexes administration command.
There are several ways to create an index in MongoDB, and from MongoDB 4.2, we can create wildcard indexes.
A wildcard index can be thought of as a kind of filter that automatically matches any field, sub-document or array in a collection and then indexes those matches.
In MongoDB, the setFeatureCompatibilityVersion command enables or disables the features that persist data incompatible with earlier versions of MongoDB.
The example on this page demonstrates how to view the featureCompatibilityVersion for a mongod instance.
When you use mongoimport to import files into MongoDB, you have the option of merging existing documents with the ones that you’re importing.
In this case, if an imported document has the same _id value as an existing one in the collection that you’re importing into, the existing document will be merged with the one being imported.
You can also specify another field (other than the _id field) to be the matching field if required.