[DOCS-10547] Docs for SERVER-142: Read-only views over collection data. Created: 18/Jul/17  Updated: 02/Oct/17  Resolved: 02/Oct/17

Status: Closed
Project: Documentation
Component/s: None
Affects Version/s: None
Fix Version/s: 3.3.12

Type: Task Priority: Major - P3
Reporter: Emily Hall Assignee: Unassigned
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Documented
documents SERVER-142 Read-only views over collection data. Closed
Participants:
Days since reply: 6 years, 30 weeks, 1 day ago

 Description   

Documentation Request Summary:

No documentation summary in engineering ticket

Engineering Ticket Description:

Issue Status as of Aug 31, 2016

ISSUE SUMMARY
MongoDB 3.3.12 adds support for creating read-only views over existing collections or other views. To specify or define a view, MongoDB introduces the viewOn and pipeline options to the existing create command:

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

In addition, there's also a mongo shell helper db.createView():

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

Views are readable via the following commands:

For more information views, as well as examples, please see the Read-only Views documentation.

Original description

Support for read-only views will consist of providing a mechanism for binding a namespace name to a (namespace name, query) pair, where the query might be a MongoDB query or an aggregation expression. For example, if you had a collection "housing.apartments", you might create a view

housing.cheapApartments = (housing.apartments, { rent: { $lte: 1000 } })

Finds on cheapApartments would only consider those elements of housing.apartments where the "rent" field was less than 1000.

By using an aggregation expression with an unwind stage, you could produce a view over a database that had one document for every member of an array in an input document, providing another means to examine and query embedded documents.


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