hile the regeneration is in progress.
	 *
	 * @return bool True if there's any product at all in the database, false otherwise.
	 */
	private function initialize_table_and_data() {
		global $wpdb;

		// phpcs:disable WordPress.DB.PreparedSQL.NotPrepared
		$wpdb->query(
			'
CREATE TABLE ' . $this->lookup_table_name . '(
  product_id bigint(20) NOT NULL,
  product_or_parent_id bigint(20) NOT NULL,
  taxonomy varchar(32) NOT NULL,
  term_id bigint(20) NOT NULL,
  is_variation_attribute tinyint(1) NOT NULL,
  in_stock tinyint(1) NOT NULL
 );
		'
		);
		// phpcs:enable WordPress.DB.PreparedSQL.NotPrepared

		$last_existing_product_id =
			WC()->call_function(
				'wc_get_products',
				array(
					'return'  => 'ids',
					'limit'   => 1,
					'orderby' => array(
						'ID' => 'DESC',
					),
				)
			);

		if ( ! $last_existing_product_id ) {
			// No products exist, nothing to (re)generate.
			return false;
		}

		$this->data_store->set_regeneration_in_progress_flag();
		update_option( 'woocommerce_attribute_lookup_last_product_id_to_process', current( $last_existing_product_id ) );
		update_option( 'woocommerce_attribute_lookup_last_products_page_processed', 0 );

		return true;
	}

	/**
	 * Action scheduler callback, performs one regeneration step and then
	 * schedules the next step if necessary.
	 */
	private function run_regeneration_step_callback() {
		if ( ! $this->data_store->regeneration_is_in_progress() ) {
			return;
		}

		$result = $this->do_regeneration_step();
		if ( $result ) {
			$this->enqueue_regeneration_step_run();
		} else {
			$this->finalize_regeneration();
		}
	}

	/**
	 * Enqueue one regeneration step in action scheduler.
	 */
	private function enqueue_regeneration_step_run() {
		$queue = WC()->get_instance_of( \WC_Queue::class );
		$queue->schedule_single(
			WC()->call_function( 'time' ) + 1,
			'woocommerce_run_product_attribute_lookup_regeneration_callback',
			array(),
			'woocommerce-db-updates'
		);
	}

	/**
	 * Perform one regeneration step: grabs a chunk of products and creates
	 * the appropriate entries for them in the lookup table.
	 *
	 * @return bool True if more steps need to be run, false otherwise.
	 */
	private function do_regeneration_step() {
		$last_products_page_processed = get_option( 'woocommerce_attribute_lookup_last_products_page_processed' );
		$current_products_page        = (int) $last_products_page_processed + 1;

		$product_ids = WC()->call_function(
			'wc_get_products',
			array(
				'limit'   => self::PRODUCTS_PER_GENERATION_STEP,
				'page'    => $current_products_page,
				'orderby' => array(
					'ID' => 'ASC',
				),
				'return'  => 'ids',
			)
		);

		if ( ! $product_ids ) {
			return false;
		}

		foreach ( $product_ids as $id ) {
			$this->data_store->create_data_for_product( $id );
		}

		update_option( 'woocommerce_attribute_lookup_last_products_page_processed', $current_products_page );

		$last_product_id_to_process = get_option( 'woocommerce_attribute_lookup_last_product_id_to_process' );
		return end( $product_ids ) < $last_product_id_to_process;
	}

	/**
	 * Cleanup/final option setup after the regeneration has been completed.
	 */
	private function finalize_regeneration() {
		delete_option( 'woocommerce_attribute_lookup_last_product_id_to_process' );
		delete_option( 'woocommerce_attribute_lookup_last_products_page_processed' );
		update_option( 'woocommerce_attribute_lookup_enabled', 'no' );
		$this->data_store->unset_regeneration_in_progress_flag();
	}

	/**
	 * Add a 'Regenerate product attributes lookup table' entry to the Status - Tools page.
	 *
	 * @param array $tools_array The tool definitions array that is passed ro the woocommerce_debug_tools filter.
	 * @return array The tools array with the entry added.
	 */
	private function add_initiate_regeneration_entry_to_tools_array( array $tools_array ) {
		$lookup_table_exists       = $this->data_store->check_lookup_table_exists();
		$generation_is_in_progress = $this->data_store->regeneration_is_in_progress();

		// Regenerate table.

		if ( $lookup_table_exists ) {
			$generate_item_name   = __( 'Regenerate the product attributes lookup table', 'woocommerce' );
			$generate_item_desc   = __( 'This tool will regenerate the product attributes lookup table data from existing product(s) data. This process may take a while.', 'woocommerce' );
			$generate_item_return = __( 'Product attributes lookup table data is regenerating', 'woocommerce' );
			$generate_item_button = __( 'Regenerate', 'woocommerce' );
		} else {
			$generate_item_name   = __( 'Create and fill product attributes lookup table', 'woocommerce' );
			$generate_item_desc   = __( 'This tool will create the product attributes lookup table data and fill it with existing products data. This process may take a while.', 'woocommerce' );
			$generate_item_return = __( 'Product attributes lookup table is being filled', 'woocommerce' );
			$generate_item_button = __( 'Create', 'woocommerce' );
		}

		$entry = array(
			'name'             => $generate_item_name,
			'desc'             => $generate_item_desc,
			'requires_refresh' => true,
			'callback'         => function() use ( $generate_item_return ) {
				$this->initiate_regeneration_from_tools_page();
				return $generate_item_return;
			},
		);

		if ( $lookup_table_exists ) {
			$entry['selector'] = array(
				'description'   => __( 'Select a product to regenerate the data for, or leave empty for a full table regeneration:', 'woocommerce' ),
				'class'         => 'wc-product-search',
				'search_action' => 'woocommerce_json_search_products',
				'name'          => 'regenerate_product_attribute_lookup_data_product_id',
				'placeholder'   => esc_attr__( 'Search for a product&hellip;', 'woocommerce' ),
			);
		}

		if ( $generation_is_in_progress ) {
			$entry['button'] = sprintf(
				/* translators: %d: How many products have been processed so far. */
				__( 'Filling in progress (%d)', 'woocommerce' ),
				get_option( 'woocommerce_attribute_lookup_last_products_page_processed', 0 ) * self::PRODUCTS_PER_GENERATION_STEP
			);
			$entry['disabled'] = true;
		} else {
			$entry['button'] = $generate_item_button;
		}

		$tools_array['regenerate_product_attributes_lookup_table'] = $entry;

		if ( $lookup_table_exists ) {

			// Delete the table.

			$tools_array['delete_product_attributes_lookup_table'] = array(
				'name'             => __( 'Delete the product attributes lookup table', 'woocommerce' ),
				'desc'             => sprintf(
					'<strong class="red">%1$s</strong> %2$s',
					__( 'Note:', 'woocommerce' ),
					__( 'This will delete the product attributes lookup table. You can create it again with the "Create and fill product attributes lookup table" tool.', 'woocommerce' )
				),
				'button'           => __( 'Delete', 'woocommerce' ),
				'requires_refresh' => true,
				'callback'         => function () {
					$this->delete_all_attributes_lookup_data();
					return __( 'Product attributes lookup table has been deleted.', 'woocommerce' );
				},
			);
		}

		return $tools_array;
	}

	/**
	 * Callback to initiate the regeneration process from the Status - Tools page.
	 *
	 * @throws \Exception The regeneration is already in progress.
	 */
	private function initiate_regeneration_from_tools_page() {
		// phpcs:ignore WordPress.Security.ValidatedSanitizedInput
		if ( ! isset( $_REQUEST['_wpnonce'] ) || false === wp_verify_nonce( $_REQUEST['_wpnonce'], 'debug_action' ) ) {
			throw new \Exception( 'Invalid nonce' );
		}

		if ( isset( $_REQUEST['regenerate_product_attribute_lookup_data_product_id'] ) ) {
			$product_id = (int) $_REQUEST['regenerate_product_attribute_lookup_data_product_id'];
			$this->check_can_do_lookup_table_regeneration( $product_id );
			$this->data_store->create_data_for_product( $product_id );
		} else {
			$this->check_can_do_lookup_table_regeneration();
			$this->initiate_regeneration();
		}
	}

	/**
	 * Enable or disable the actual lookup table usage.
	 *
	 * @param bool $enable True to enable, false to disable.
	 * @throws \Exception A lookup table regeneration is currently in progress.
	 */
	private function enable_or_disable_lookup_table_usage( $enable ) {
		if ( $this->data_store->regeneration_is_in_progress() ) {
			throw new \Exception( "Can't enable or disable the attributes lookup table usage while it's regenerating." );
		}

		update_option( 'woocommerce_attribute_lookup_enabled', $enable ? 'yes' : 'no' );
	}

	/**
	 * Check if everything is good to go to perform a complete or per product lookup table data regeneration
	 * and throw an exception if not.
	 *
	 * @param mixed $product_id The product id to check the regeneration viability for, or null to check if a complete regeneration is possible.
	 * @throws \Exception Something prevents the regeneration from starting.
	 */
	private function check_can_do_lookup_table_regeneration( $product_id = null ) {
		if ( $product_id && ! $this->data_store->check_lookup_table_exists() ) {
			throw new \Exception( "Can't do product attribute lookup data regeneration: lookup table doesn't exist" );
		}
		if ( $this->data_store->regeneration_is_in_progress() ) {
			throw new \Exception( "Can't do product attribute lookup data regeneration: regeneration is already in progress" );
		}
		if ( $product_id && ! wc_get_product( $product_id ) ) {
			throw new \Exception( "Can't do product attribute lookup data regeneration: product doesn't exist" );
		}
	}
}