Support sqlite alter table drop column when applying new schema

[alarbada]

Sqlite supports dropping columns for a while now.

I was surprised to see that atlas still migrates the old way, removing and creating the table again.

[a8m]

Thanks for bringing this up, @alarbada. DROP COLUMN is allowed only with a few limitations:

The DROP COLUMN command only works if the column is not referenced by any other parts of the schema and is not a PRIMARY KEY and does not have a UNIQUE constraint. Possible reasons why the DROP COLUMN command can fail include:

The column is a PRIMARY KEY or part of one.
The column has a UNIQUE constraint.
The column is indexed.
The column is named in the WHERE clause of a partial index.
The column is named in a table or column CHECK constraint not associated with the column being dropped.
The column is used in a foreign key constraint.
The column is used in the expression of a generated column.
The column appears in a trigger or view.

However, this can still be improved. I've assigned it to myself, and we will add it to the upcoming milestones.