Uploaded image for project: 'Documentation'
  1. Documentation
  2. DOCS-12028

New syntax for $out aggregation stage

    XMLWordPrintable

    Details

    • Type: Task
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 4.1.3
    • Component/s: Server
    • Labels:
      None

      Description

      Description

      Document the updated syntax for the $out aggregation stage. The specific syntax has changed between 4.1.1 and 4.1.2, with additional functionality added in 4.1.3. Some functionality may have been backported to 4.0.x. Check the corresponding server ticket for each $out related change to look for any backport work done.

      The current syntax for $out is: 

      { $out : <collection name> }

       

      Based on the technical design in WRITING-1983 and the updates in SERVER-36286 (4.1.2) ( based on this code chunk ), the updated syntax for $out should be:

      {
        $out: {
          to : <string collection name>,
          mode : "insertDocuments" | "replaceDocuments" | "replaceCollection",
          db : "<destination database, if different from current db>",
          uniqueKey: { optional document of fields that identifies a document for replacement or merge }
        }
      }

       

      WRITING-1983 contains significant amounts of behavioral descriptions that should be taken into account when updating the current $out page. Take special care when documenting the behavior of uniqueKey.

      As of SERVER-36123, $out does not support outputting to a sharded collection if  mode : "replaceCollection

      As of SERVER-18027, $out does support outputting to a sharded collection if mode : "insertDocuments|replaceDocuments"

      SERVER-35954, SERVER-36100, SERVER-36424: describes the behavior of the optional uniqueKey field for sharded collections

      Other tickets may come through related to additional behavior of $out. There's some confusion over exactly what versions behavior has been ported to. Focus on what is going into 4.2, but make note of any features (e.g. SERVER-36123) that have been marked with a 4.0.x fix version. Confirm with the engineers what features specifically will/have been backported, if any.

      See https://jira.mongodb.org/browse/PM-828 for a complete list of all tickets related to $out
       

      Scope of changes

        • You can find the source file in source/reference/operator/aggregation/out.txt
      • Use https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/ as a model to work off of
        • You can find the source file in source/reference/operator/aggregation/lookup.txt. Take note of how we use .. include:: directive and the files it points to, how they are structured, etc. 

        Attachments

          Issue Links

            Activity

              People

              Assignee:
              isabella.siu Isabella Siu
              Reporter:
              ravind.kumar Ravind Kumar (Inactive)
              Participants:
              Last commenter:
              Githook User Githook User
              Votes:
              0 Vote for this issue
              Watchers:
              3 Start watching this issue

                Dates

                Created:
                Updated:
                Resolved:
                Days since reply:
                1 year, 45 weeks, 2 days ago
                Date of 1st Reply: