Dry run migrations.

[igalklebanov]

Hey 👋

What if we could dry-run migrations?

[shane-js]

So awesome to see this presented as a possibility after our talk yesterday. I'll share what I wrote there:

[Without this my] current thought is the only way to test is by wiping the DB completely (or point to a different one) and re-backing it up to compare the schema of the rewritten kysely migration to the original schema created by the knex migration.

I've always longed for something like Entity Framework how it can compare and show diffs before executing.

Although I am guessing technically this would only be possible incrementally with each currently unrun migration file - it would be insanely great if it could output what the final diffs would be after all migrations something like (example of edit column, delete column, and insert column only others would need thought out):

UserTable:

• first_name varchar(255) ✏️ varchar(1000)
• midd1e_name varchar(1000) -> ❌
• middle_name varchar(1000) -> ✅

I honestly think something like this would be extremely well received and attract a lot of people to this tech if it could be figured out.

[EloB]

Is this considered? Would love to have such feature. Just to see all queries that would be executed before I run them.

@shane-js Like your stuff as well but just able to see what will be executed in SQL would be amazing.

[igalklebanov]

This could work for databases that support transactional DDL.

Run the command and rollback, while logging what ran.

For others, not sure yet, maybe setup a shadow/in-memory database to run against. Maybe just a temporary schema on the existing one.