Different cases of partial resync

Partial sync resyncs a specific range of rows from a source table into the target. Data is exported from the source into a temporary staging area, loaded into a temp table on the target, and then merged with the existing target table. The behaviour varies depending on column differences and the hard_delete setting.

Note

Partial sync uses the PartialSync component of FastSync. It shares the same native database connectors as FullSync but applies a WHERE clause during export and merges (rather than replaces) the target data.

1. Normal

All source columns exist in the target. The exported rows are merged into the target table, updating existing rows and inserting new ones. This is the standard case.

2. Some columns are deleted from the target

A column (e.g. Col2) has been removed from the target table. After merging, only the rows within the synced range will have values for that column — existing rows outside the range retain their original data.

3. Some columns are deleted from the source

A column (e.g. Col2) has been removed from the source table. Since the column no longer exists in the exported data, merged rows will have NULL for that column in the target. Rows outside the synced range are not affected.

4. Hard delete is disabled (soft delete)

When hard_delete is false, rows that have been deleted from the source are not removed from the target. Instead, they receive a timestamp in the _SDC_DELETED_AT metadata column indicating when the delete was detected.

5. Hard delete is enabled

When hard_delete is true, rows that have been deleted from the source within the synced range are physically removed from the target table.

6. Combination of all cases

This diagram shows the combined effect of column differences and delete handling when all of the above scenarios overlap.