You NEVER do that in one go, you need to split it in several deployments. Dropping a column is relatively straightforward, in two steps. First deploy a version of the code that doesn’t use the column, then release the migration dropping the column.
The typical example is the renaming of a column, which needs to be done in several steps:
1. Create the new column, copying the data from the old column (DB migration) both columns exist, but only the old one is used
2. Deploy new code that works with both columns, reading from old and writing new and old
3. Deploy data migration (DB migration) that ensures old and new columns has the same values (to ensure data consistency). At this point, there are no “old column only” writes by the code deployed in previous step
4. Deploy new code using only new column. Old column is deprecated
5. Delete old column
At any given point, code versions N (current) and N-1 (previous) are compatible with the DB. Any change on the DB is done in advance in a backwards compatible way.
The typical example is the renaming of a column, which needs to be done in several steps:
1. Create the new column, copying the data from the old column (DB migration) both columns exist, but only the old one is used
2. Deploy new code that works with both columns, reading from old and writing new and old
3. Deploy data migration (DB migration) that ensures old and new columns has the same values (to ensure data consistency). At this point, there are no “old column only” writes by the code deployed in previous step
4. Deploy new code using only new column. Old column is deprecated
5. Delete old column
At any given point, code versions N (current) and N-1 (previous) are compatible with the DB. Any change on the DB is done in advance in a backwards compatible way.