IssueTracker

Component used: androidx.room

Version used: 2.6.1

Adding a column to a table is a common migration scenario, where the new column has one of these requirements:

1. Nullable
2. Not null with default value
3. Not null without default value

1 and 2 can be handled with auto-migrations. 2 requires the new property being annotated with e.g. @ColumnInfo(defaultValue = "").

Scenario 3 - while arguably not less common - is not covered by auto-migrations.

Instead it requires a manual migration executing multiple SQL statements:

• Step 1: Create a new table with the new schema
• Step 2: Copy data from old table to new table and assign a value to the new column
• Step 3: Drop the old table
• Step 4: Rename the new table to match the original table name

What I would like to see is 3 being covered by an auto-migration with an auto-migration-spec annotation, which allows for defining a default value (for the migration only). It could look like this:

@AddNotNullColumn(tableName = "User", columnName = "AppUser", migrationDefaultValue = "")

This by itself would cover a lot of cases. In case the column needs to be populated with dynamic values, a manual migration could be appended which would be way easier (basically only step 3 from above).

This could be implemented with the steps shown above but spare the app developer from the complexity. I'd appreciate if you'd consider it.