Perform a Delta Lake MERGE upsert with WHEN NOT MATCHED BY SOURCE to handle deletes from a CDC source

Steps

1. Load the CDC source data into a Delta DataFrame or temp view containing inserts, updates, and deletes with a change_type indicator column.
2. Write the MERGE statement: MERGE INTO delta.`/path/to/customers` t USING cdc_source s ON t.id = s.id WHEN MATCHED AND s.change_type = 'delete' THEN DELETE WHEN MATCHED THEN UPDATE SET * WHEN NOT MATCHED THEN INSERT * WHEN NOT MATCHED BY SOURCE THEN DELETE.
3. The WHEN NOT MATCHED BY SOURCE clause deletes rows in the target that are absent from the source, enabling full-table sync semantics.
4. Add predicates to both the MERGE condition and individual WHEN clauses to limit the scan and rewrite scope to specific partitions.
5. After the MERGE, run DESCRIBE HISTORY delta.`/path/to/customers` to confirm the MERGE operation was recorded with the correct operationMetrics.