Loop through all MongoDB collections and execute query?

To loop through all MongoDB collections and execute a query, use db.getCollectionNames() to retrieve collection names, then iterate using forEach() to perform operations on each collection.

Syntax

db.getCollectionNames().forEach(function(collectionName) {
    // Execute your query on each collection
    var result = db[collectionName].find(query);
    // Process the result
});

Example: Get Latest Document from Each Collection

Loop through all collections and get the timestamp of the most recent document ?

db.getCollectionNames().forEach(function(collectionName) {
    var latest = db[collectionName].find().sort({_id:-1}).limit(1);
    if (latest.hasNext()) {
        printjson(latest.next()._id.getTimestamp());
    }
});

The output shows the creation timestamp of the latest document from each collection ?

ISODate("2019-02-21T18:52:43Z")
ISODate("2019-03-19T17:49:00Z")
ISODate("2019-03-06T15:40:12Z")
ISODate("2019-03-15T16:31:50Z")
ISODate("2019-02-21T15:40:52Z")
ISODate("2019-03-06T06:14:37Z")
ISODate("2019-02-21T19:29:15Z")
ISODate("2019-03-15T13:35:33Z")
ISODate("2019-03-14T21:13:58Z")
ISODate("2019-03-18T22:02:54Z")
ISODate("2019-03-22T18:01:45Z")
ISODate("2019-03-06T16:21:14Z")

How It Works

• db.getCollectionNames() returns an array of all collection names in the database
• forEach() iterates through each collection name
• db[collectionName] dynamically accesses each collection
• sort({_id:-1}).limit(1) gets the most recent document by ObjectId
• hasNext() checks if the collection has documents before processing

Conclusion

Use db.getCollectionNames().forEach() to iterate through all collections and execute queries dynamically. This approach is useful for database maintenance tasks and cross-collection operations.