Metadata columns

PostgreSQL and Snowflake targets automatically add _SDC_ columns that describe ingestion time and source-delete events.

Columns

Column	Meaning
_SDC_EXTRACTED_AT	Time the tap extracted the record.
_SDC_BATCHED_AT	Time the record entered a target load batch.
_SDC_DELETED_AT	Time a source delete event was received; NULL for active rows.

Source deletes

_SDC_DELETED_AT is an internal deletion marker. PostgreSQL and Snowflake targets physically remove marked rows before acknowledging Singer state.

Only LOG_BASED replication emits individual source-delete events. Key-based incremental replication cannot detect deleted source rows. FullSync replaces the target table, while PartialSync removes target rows that are missing from its selected source range. Singer FULL_TABLE behaviour remains connector-specific.