Investigate changes in PM-1950: Improved change stream event visibility for C2C Replication

1. $changeStream stage accepts new boolean parameters: showExpandedEvents, showSystemEvents and showRawUpdateDescription. The latter two flags are internal and not documented.
2. New types of events are reported when requested.
3. Some of the existing events are reported in more cases and have additional fields.
4. New internal aggregation stage is added to apply updates described in the oplog format
5. Changes to the update description

Please see Syntax doc for more details.

Description of Linked Ticket

Summary

Expose additional change events and improve existing change events to enable cluster to cluster replication

Motivation

As part of the proposed architecture for Cluster to Cluster (C2C) Replication, changes are replicated using change streams instead of oplog tailing and applyOps. However, change stream currently doesn't expose enough information (e.g. DDL operations, updateDescription) for change events to be used for replication. This project is to improve change stream event visibility to enable change-stream-based C2C replication.

Cast of Characters

• Product Owner: Katya Kamenieva
• Project Lead: Arun Banala
• Program Manager: Ana Meza
• Drivers Contact:

Documentation

Scope Document
Syntax Document
Technical Design Document
Product Description

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