Core Platform Team/Initiatives/MCR schema migration
MCR schema migration
Complete the schema migration tasks associated with the Multi-Content Revisions (MCR) project.
- Significance and Motivation
This initiative is necessary to remove the tech debt remaining from the pre-MCR schema.
Writing to pre-MCR fields is disabled in WMF production. Pre-MCR fields can be dropped from the database at the discretion of DBAs. All code that writes pre-MCR fields has been removed from core.
- Baseline Metrics
Some core in core and extensions still relies on information in pre-MCR fields in the database. This makes it impossible to stop writing to these fields.
- Target Metrics
All code that accesses pre-MCR fields in the database is removed or gated with the MCR migration stage. This applies to core as well as deployed extensions and bundled extensions.
core developers, database admins
- Known Dependencies/Blockers
Epics, User Stories, and Requirements
- EPIC T231671: Ensure all direct or indirect access to pre-MCR fields is gated with the MCR migration stage.
- EPIC T231672: Stop writing to pre-MCR fields in WMF production (no coding, just config - and fixing bugs)
- USER STORY T183487: MCR schema migration stage 3: stop using legacy fields
- EPIC T231673: Make SCHEMA_COMPAT_NEW the default MCR migration schema (trivial change, really, but conceptually a milestone)
- target 1.34
- T214308 Force usage of MCR aware database schema
- make sure update.php works right!
- EPIC T231674: Remove the ability to write pre-MCR fields, limit the ability to read pre-MCR fields to migration scripts. Remove the MCR migration stage config variable
- target 1.35
- T198557 Remove support for writing to the pre-MCR schema
- Remove migration stage setting
- Other Documents