What exactly is the CD2 migration_id and how is it meant to be used?

[jhveem]

Problem

I've noticed there are entries in most course content items for a migration_id. My assumption was this was a way to join with the content_migrations table, but the id in that table doesn't match the format of the migration_id. 

What I'm Trying to Do

I'd first off just like to understand what the migration_id and content_migrations.id are meant to do. As an example of a specific project, I'd like to look up a given assignment/quiz/page/etc. and track that content item back to the course where it was originally created through its content_migrations. However, since the migration_id and content_migrations.id don't appear to be related, I'm stumped.

TLDR;

Is there a relationship between a content item's (assignment/quiz/page/etc.) migration_id and content_migrations.id?

If not, what are they meant to be used for?

Is there a way to see which course a content item came from (whether through migration_ids or something else?)

I assume I'm missing something obvious, but if someone could point me in the right direction, that would be great.

Thanks!

[stimme]

Hi @jhveem ! The migration_id appears to be a key for master_courses_master_migrations.id. It should appear for content created by Blueprint syncs according to the CD2 documentation.

[jhveem]

Thanks, I looked through the documentation, and I don't think that's quite right. The migration_id field descriptions I checked don't mention blueprints, and I checked several quizzes in our cd2 that I know for sure didn't come from blueprint migrations and they have a migration id (~90% of all our content has a migration id and we only have about a dozen blueprints). But I think you're in the right direction.

My working theory, assuming I understand the docs, is that this is a unique identifier used for any content copied in any way (blueprint syncs, course copy, content import, etc.) that Canvas uses to determine if a migration should replace existing content or create something new.

[stimme]

This sounds right. The note for assignments.migration_id indicates as much. The note for wiki_pages.migration_id says it is related to blueprints. But I think that must be wrong, because the vast majority of our pages have migration_ids, and very few of our courses are associated to blueprints.

[sgergely]

The Entity Relationship Diagram might help you in that question I beleive: https://data-access-platform-api.s3.amazonaws.com/erd/index.html

[jhveem]

Thanks, I checked a few content types, but according to that, the Migration Id it isn't related to anything.