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db.createView()

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  • Syntax
  • Examples
  • Behavior
db.createView()

Note

Disambiguation

This page discusses standard views. For discussion of on-demand materialized views, see On-Demand Materialized Views.

To understand the differences between the view types, see Comparison with On-Demand Materialized Views.

Creates a view as the result of the applying the specified aggregation pipeline to the source collection or view. Views act as read-only collections, and are computed on demand during read operations. You must create views in the same database as the source collection. MongoDB executes read operations on views as part of the underlying aggregation pipeline.

A view definition pipeline cannot include the $out or the $merge stage. This restriction also applies to embedded pipelines, such as pipelines used in $lookup or $facet stages.

Syntax

db.createView has the following syntax:

db.createView(<view>, <source>, <pipeline>, <collation>)

The method has the following parameters:

Parameter
Type
Description
view
string
The name of the view to create.
source
string
The name of the source collection or view from which to create the view. The name does not include the database name and implies the same database as the view to create; it is not the full namespace of the collection or view. You must create views in the same database as the source collection.
pipeline
array

An array that consists of the aggregation pipeline stage(s). db.createView() creates the view by applying the specified pipeline to the source collection or view.

A view definition pipeline cannot include the $out or the $merge stage. This restriction also applies to embedded pipelines, such as pipelines used in $lookup or $facet stages.

The view definition is public; i.e. db.getCollectionInfos() and explain operations on the view will include the pipeline that defines the view. As such, avoid referring directly to sensitive fields and values in view definitions.

collation
document

Optional. Specifies the default collation for the view.

Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks.

If the underlying source is a collection, the view does not inherit the collection's collation settings.

If no collation is specified, the view's default collation is the "simple" binary comparison collator.

If the underlying source is another view, the view must specify the same collation settings.

The collation option has the following syntax:

collation: {
   locale: <string>,
   caseLevel: <boolean>,
   caseFirst: <string>,
   strength: <int>,
   numericOrdering: <boolean>,
   alternate: <string>,
   maxVariable: <string>,
   backwards: <boolean>
}

When specifying collation, the locale field is mandatory; all other collation fields are optional. For descriptions of the fields, see Collation Document.

The db.createView() method wraps the following create command operation:

db.runCommand( { create: <view>, viewOn: <source>, pipeline: <pipeline>, collation: <collation> } )

Important

View Names are Included in Collection List Output

Operations that list collections, such as db.getCollectionInfos() and db.getCollectionNames(), include views in their outputs.

The view definition is public; i.e. db.getCollectionInfos() and explain operations on the view will include the pipeline that defines the view. As such, avoid referring directly to sensitive fields and values in view definitions.

Examples

To see examples of creating a view, see the following pages:

Behavior

To see behavioral details of views, see Behavior.

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