{% macro apply_snapshot_backfill(snapshot_ref, backfill_ref, primary_key) %}
	{% if execute %}
		{% if relation_exists(snapshot_ref) and relation_exists(backfill_ref)%}
			INSERT INTO {{ snapshot_ref }} 
				(
				{{ column_intersect(snapshot_ref, backfill_ref,exclude=["dbt_scd_id", "dbt_updated_at", "dbt_valid_from", "dbt_valid_to"], quote_identifiers=false)| list | join(",") }}
				, dbt_scd_id, dbt_updated_at, dbt_valid_from, dbt_valid_to)
			SELECT 
				{{ column_intersect(snapshot_ref, backfill_ref,exclude=["dbt_scd_id", "dbt_updated_at", "dbt_valid_from", "dbt_valid_to"])| list | join(",") }} ,
				b.dbt_scd_id,
				b.dbt_updated_at,
				b.dbt_valid_from,
				--doesnt handle deleted rows...
				least(b.dbt_valid_to, min_from) as dbt_valid_to
			FROM {{ backfill_ref }} b
			LEFT JOIN (	
				SELECT MIN(dbt_valid_from) as min_from, {{ primary_key }}
				FROM {{ snapshot_ref }} 
				GROUP BY {{ primary_key }} 
			) c
			USING ({{ primary_key }})
			WHERE b.dbt_valid_from < coalesce(min_from, current_timestamp); -- only insert earlier backfill rows OR any backfill entities that no longer exist.
		{% endif %}
	{% endif %}
{% endmacro %}