The collation introduced in version MongoDB 3.4. Maybe, you implemented collation in a previous version.
For our example, we are using MongoDB version 4.0.5. Following is the query to check the current version on system −
> db.version()
This will produce the following output −
4.0.5
Let us first create a collection with documents −
> db.collationExample.createIndex({Value: 1}, {collation: {locale: "en", strength: 1}}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.collationExample.insertOne({'Value':'x'}); { "acknowledged" : true, "insertedId" : ObjectId("5e038a3cf5e889d7a51994f5") } > db.collationExample.insertOne({'Value':'X'}); { "acknowledged" : true, "insertedId" : ObjectId("5e038a48f5e889d7a51994f6") } > db.collationExample.insertOne({'Value':'Y'}); { "acknowledged" : true, "insertedId" : ObjectId("5e038a49f5e889d7a51994f7") } > db.collationExample.insertOne({'Value':'a'}); { "acknowledged" : true, "insertedId" : ObjectId("5e038a49f5e889d7a51994f8") } > db.collationExample.insertOne({'Value':'á'}); { "acknowledged" : true, "insertedId" : ObjectId("5e038a4bf5e889d7a51994f9") }
Following is the query to display all documents from a collection with the help of find() method −
> db.collationExample.find().pretty();
This will produce the following output −
{ "_id" : ObjectId("5e038a3cf5e889d7a51994f5"), "Value" : "x" } { "_id" : ObjectId("5e038a48f5e889d7a51994f6"), "Value" : "X" } { "_id" : ObjectId("5e038a49f5e889d7a51994f7"), "Value" : "Y" } { "_id" : ObjectId("5e038a49f5e889d7a51994f8"), "Value" : "a" } { "_id" : ObjectId("5e038a4bf5e889d7a51994f9"), "Value" : "á" }
Here is the query to use COLLATION() −
> db.collationExample.find({ Value: "a" } ).collation( { locale: "en", strength: 1 } );
This will produce the following output −
{ "_id" : ObjectId("5e038a49f5e889d7a51994f8"), "Value" : "a" } { "_id" : ObjectId("5e038a4bf5e889d7a51994f9"), "Value" : "á" }