Module db_migration 

Schema migration support

Our basic approach:

The 12-step process from s7 in https://sqlite.org/lang_altertable.html “Making Other Kinds Of Table Schema Changes” (retrieved 2025-10-12).

But we do it to the whole db at once, and we store the temporary copy in a whole temporary database which we ATTACH. So we don’t rename the tables.

So the procedure is (roughly):

• Attach temporary database
• Create tables in temporary database by running (new) schema on it
• Copy data from real to temporary database, with data alteration/supplementation as needed (including sqlite_sequence table but not other sqlite_* tables).
• Drop every table in the real database.
• Create tables in real database by running schema on it.
• Copy data from temporary database back to main database.

Structs

Migration

MigrationData

Schema

Enums

Exception

OnComplete

Outcome

Functions

migration_core

prepare_idempotent

Ensure that the database has a suitable schema