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  1. Drivers
  2. DRIVERS-776

Support 'let' option for aggregate command

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    • Spec Change
    • Status: Closed
    • Major - P3
    • Resolution: Done
    • CRUD
    • None
    • Needed
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      Added let parameters to the aggregate command.

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      Added let parameters to the aggregate command.

    Description

      Downstream Change Summary

      Drivers should add a new let option to aggregate helper methods and sync CRUD unified spec tests with mongodb/specifications@3a58fc6.

      For MongoDB 5.0+, the aggregate command accepts a let option of type object. This object consists of any amount of parameter names each followed by definitions of constants in the MQL Aggregate Expression language. Each parameter name is then usable to access the value of the corresponding MQL Expression with the "$$" syntax within Aggregate Expression contexts which may require the use of $expr or a pipeline.

      Note: this ticket only pertains to changes for aggregate. Support for let in other commands (involving pipelines or $expr) will be handled by DRIVERS-1788.

      Description of Linked Ticket

      Epic Summary

      Summary

      Deprecate the MR command and ensure its functionality is fully supported by Agg. The backend of the command has already been replaced by “MapReduce in Agg” (PM-776), we need to make sure all necessary concepts can be expressed in MQL.

      Motivation

      One objective of the query team is to consolidate dialects of all existing query commands into a single language. This project enables users to write their MR tasks directly in Agg, which provides a more capable and clear syntax. We want to move users away from legacy ways of interacting with the system. Independently, from MR jobs, some extensions are valuable for the users.

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              jmikola@mongodb.com Jeremy Mikola
              backlog-server-pm Backlog - Core Eng Program Management Team
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