Why Do Deleted Source Columns Still Appear in the Destination?

Question

Why do deleted source columns still appear in the destination?

Environment

All source databases and destinations.

Answer

In most cases, when you delete a column from the source, we keep the column in the destination with the data that existed before the deletion. From that point forward, we write NULL values into the column.

However, for some connectors, when you delete a source column, all values in the destination column are replaced with NULL instead of preserving the historical values. For more information, see our documentation on column changes. .

When a column's data type changes

When a column's data type changes, we drop and re-create the column. However, if your destination contains views referencing the old column, we can't drop it. This can leave you with two versions of the same column, and one of them no longer exists in the source. To learn more, see Why Do Some Destination Column Names Include the Suffix _deprecated?

How to drop columns by schema configuration

For some connectors, such as Salesforce, you can drop columns from your destination by excluding them from your connection schema:

1. In Fivetran, go to your connection page.
2. Select the Schema tab.
3. Deselect the checkbox next to the column you want to drop.
4. Click Save changes.
5. If supported, a pop-up window appears. Select the checkbox next to Drop blocked columns.
6. Click Save & Apply.