public function parse_relative_field( $value ) {
		global $wpdb;

		if ( empty( $value ) ) {
			return '';
		}

		// IDs are prefixed with id:.
		if ( preg_match( '/^id:(\d+)$/', $value, $matches ) ) {
			$id = intval( $matches[1] );

			// If original_id is found, use that instead of the given ID since a new placeholder must have been created already.
			$original_id = $wpdb->get_var( $wpdb->prepare( "SELECT post_id FROM {$wpdb->postmeta} WHERE meta_key = '_original_id' AND meta_value = %s;", $id ) ); // WPCS: db call ok, cache ok.

			if ( $original_id ) {
				return absint( $original_id );
			}

			// See if the given ID maps to a valid product allready.
			$existing_id = $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM {$wpdb->posts} WHERE post_type IN ( 'product', 'product_variation' ) AND ID = %d;", $id ) ); // WPCS: db call ok, cache ok.

			if ( $existing_id ) {
				return absint( $existing_id );
			}

			// If we're not updating existing posts, we may need a placeholder product to map to.
			if ( ! $this->params['update_existing'] ) {
				$product = wc_get_product_object( 'simple' );
				$product->set_name( 'Import placeholder for ' . $id );
				$product->set_status( 'importing' );
				$product->add_meta_data( '_original_id', $id, true );
				$id = $product->save();
			}

			return $id;
		}

		$id = wc_get_product_id_by_sku( $value );

		if ( $id ) {
			return $id;
		}

		try {
			$product = wc_get_product_object( 'simple' );
			$product->set_name( 'Import placeholder for ' . $value );
			$product->set_status( 'importing' );
			$product->set_sku( $value );
			$id = $product->save();

			if ( $id && ! is_wp_error( $id ) ) {
				return $id;
			}
		} catch ( Exception $e ) {
			return '';
		}

		return '';
	}