Create a View with Default Collation

Collation allows you to specify language-specific rules for string comparison, such as rules for letter-case and accent marks.

This page explains how to specify a default collation for a view.

Use a default view collation when string comparison rules, such as accent or letter-case handling, must be consistent for every query that reads from the view.

Example

Create a places collection with the following documents:

db.places.insertMany([
   { _id: 1, category: "café" },
   { _id: 2, category: "cafe" },
   { _id: 3, category: "cafE" }
])

The following operation creates a view, specifying collation at the view level:

db.createView(
   "placesView",
   "places",
   [ { $project: { category: 1 } } ],
   { collation: { locale: "fr", strength: 1 } }
)

The following operation uses the view’s collation:

db.placesView.countDocuments( { category: "cafe" } )

The operation returns 3.

• You can specify a default collation for a view at creation time. If no collation is specified, the view’s default collation is the “simple” binary comparison collator. That is, the view does not inherit the collection’s default collation.

• String comparisons on the view use the view’s default collation. An operation that attempts to change or override a view’s default collation will fail with an error.

• If creating a view from another view, you cannot specify a collation that differs from the source view’s collation.

• If performing an aggregation that involves multiple views, such as with $lookup or $graphLookup, the views must have the same collation.