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.
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Database Management Systems
How unhideIndex() Works in MongoDB
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.
Continue readingHow hideIndex() Works in MongoDB
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.
3 Ways to Create an Index in MongoDB
In MongoDB, you can create an index on a collection using the createIndex() method, the createIndexes() method, or the createIndexes administration command.
Create a Wildcard Index in MongoDB
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.
Continue readingHow to Set the featureCompatibilityVersion in MongoDB
In MongoDB, the setFeatureCompatibilityVersion command enables or disables the features that persist data incompatible with earlier versions of MongoDB.
How to View your featureCompatibilityVersion in MongoDB
The example on this page demonstrates how to view the featureCompatibilityVersion for a mongod instance.
How to Merge Documents when Importing a File into MongoDB
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.
How to Replace Existing Documents when Importing a File into MongoDB
When you use mongoimport to import files into MongoDB, you have the option of replacing existing documents that match the ones you’re importing.
By this I mean, if an imported document has the same _id value as an existing one in the collection you’re importing into, the existing document will be replaced with the one being imported.
You can also specify another field (other than the _id field) to be the matching field if required.
The way to replace existing documents when using mongoimport is to use upsert mode.
Import a CSV File into MongoDB with mongoimport
When using MongoDB, you can use mongoimport to import documents into a collection. mongoimport is a command line utility that imports content from an Extended JSON, CSV, or TSV file. The import file could have been created by mongoexport or some other export utility.
This article presents examples of importing a CSV file into MongoDB.
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