How to format down.sql when nothing in migration needs to be reverted?

[rhigman]

Backend

PostgreSQL

Diesel version

2.3.7

Diesel Features

"postgres", "uuid", "chrono", "r2d2", "64-column-tables", "serde_json"

Operating System Version

No response

Third party libraries

No response

What do you want to do?

I want to write a very small migration, where the only line in the up.sql adds a value to an existing enum type:

ALTER TYPE name_of_enum ADD VALUE IF NOT EXISTS 'name_of_value';

Because deleting existing values from enum types is not straightforward, I don't want to bother making any database changes when reverting the migration.

However, every migration has to have a down.sql file, and reverting the migration fails if that file is empty.

What should I put in the down.sql file for the migration to "revert" successfully?

Forum searches suggest BEGIN;COMMIT; as a "noop" equivalent for PostgreSQL (NULL exists, but can only be used within branching statements). However, this fails with the error "Cannot perform this operation outside of a transaction" (hitting #4854, I think).

Compile time error

No response

What code do you already have?

No response

Additional details

No response

Checklist

• I have already looked over the issue tracker and the discussion forum for similar possible closed issues.

[weiznich]

I often use just SELECT 1 in such cases. It just wants any query there.

That written: It also might be meaningful to check if a migration would be literally empty and in that case just don't do anthing there, although we might want to emit a warning as that might not be desired? I'm happy to review a PR for that.