string $taxonomy, int $term_id, bool $is_variation_attribute, bool $has_stock ) {
		global $wpdb;

		// phpcs:disable WordPress.DB.PreparedSQL.NotPrepared
		$wpdb->query(
			$wpdb->prepare(
				'INSERT INTO ' . $this->lookup_table_name . ' (
					  product_id,
					  product_or_parent_id,
					  taxonomy,
					  term_id,
					  is_variation_attribute,
					  in_stock)
					VALUES
					  ( %d, %d, %s, %d, %d, %d )',
				$product_id,
				$product_or_parent_id,
				$taxonomy,
				$term_id,
				$is_variation_attribute ? 1 : 0,
				$has_stock ? 1 : 0
			)
		);
		// phpcs:enable WordPress.DB.PreparedSQL.NotPrepared
	}

	/**
	 * Handler for the woocommerce_rest_insert_product hook.
	 * Needed to update the lookup table when the REST API batch insert/update endpoints are used.
	 *
	 * @param \WP_Post         $product The post representing the created or updated product.
	 * @param \WP_REST_Request $request The REST request that caused the hook to be fired.
	 * @return void
	 */
	private function on_product_created_or_updated_via_rest_api( \WP_Post $product, \WP_REST_Request $request ): void {
		if ( StringUtil::ends_with( $request->get_route(), '/batch' ) ) {
			$this->on_product_changed( $product->ID );
		}
	}

	/**
	 * Tells if a lookup table regeneration is currently in progress.
	 *
	 * @return bool True if a lookup table regeneration is already in progress.
	 */
	public function regeneration_is_in_progress() {
		return get_option( 'woocommerce_attribute_lookup_regeneration_in_progress', null ) === 'yes';
	}

	/**
	 * Set a permanent flag (via option) indicating that the lookup table regeneration is in process.
	 */
	public function set_regeneration_in_progress_flag() {
		update_option( 'woocommerce_attribute_lookup_regeneration_in_progress', 'yes' );
	}

	/**
	 * Remove the flag indicating that the lookup table regeneration is in process.
	 */
	public function unset_regeneration_in_progress_flag() {
		delete_option( 'woocommerce_attribute_lookup_regeneration_in_progress' );
	}

	/**
	 * Set a flag indicating that the last lookup table regeneration process started was aborted.
	 */
	public function set_regeneration_aborted_flag() {
		update_option( 'woocommerce_attribute_lookup_regeneration_aborted', 'yes' );
	}

	/**
	 * Remove the flag indicating that the last lookup table regeneration process started was aborted.
	 */
	public function unset_regeneration_aborted_flag() {
		delete_option( 'woocommerce_attribute_lookup_regeneration_aborted' );
	}

	/**
	 * Tells if the last lookup table regeneration process started was aborted
	 * (via deleting the 'woocommerce_attribute_lookup_regeneration_in_progress' option).
	 *
	 * @return bool True if the last lookup table regeneration process was aborted.
	 */
	public function regeneration_was_aborted(): bool {
		return get_option( 'woocommerce_attribute_lookup_regeneration_aborted' ) === 'yes';
	}

	/**
	 * Check if the lookup table contains any entry at all.
	 *
	 * @return bool True if the table contains entries, false if the table is empty.
	 */
	public function lookup_table_has_data(): bool {
		global $wpdb;

		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
		return ( (int) $wpdb->get_var( "SELECT EXISTS (SELECT 1 FROM {$this->lookup_table_name})" ) ) !== 0;
	}

	/**
	 * Handler for 'woocommerce_get_sections_products', adds the "Advanced" section to the product settings.
	 *
	 * @param array $products Original array of settings sections.
	 * @return array New array of settings sections.
	 */
	private function add_advanced_section_to_product_settings( array $products ): array {
		if ( $this->check_lookup_table_exists() ) {
			$products['advanced'] = __( 'Advanced', 'woocommerce' );
		}

		return $products;
	}

	/**
	 * Handler for 'woocommerce_get_settings_products', adds the settings related to the product attributes lookup table.
	 *
	 * @param array  $settings Original settings configuration array.
	 * @param string $section_id Settings section identifier.
	 * @return array New settings configuration array.
	 */
	private function add_product_attributes_lookup_table_settings( array $settings, string $section_id ): array {
		if ( 'advanced' === $section_id && $this->check_lookup_table_exists() ) {
			$title_item = array(
				'title' => __( 'Product attributes lookup table', 'woocommerce' ),
				'type'  => 'title',
			);

			$regeneration_is_in_progress = $this->regeneration_is_in_progress();

			if ( $regeneration_is_in_progress ) {
				$title_item['desc'] = __( 'These settings are not available while the lookup table regeneration is in progress.', 'woocommerce' );
			}

			$settings[] = $title_item;

			if ( ! $regeneration_is_in_progress ) {
				$regeneration_aborted_warning =
					$this->regeneration_was_aborted() ?
						sprintf(
							"<p><strong style='color: #E00000'>%s</strong></p><p>%s</p>",
							__( 'WARNING: The product attributes lookup table regeneration process was aborted.', 'woocommerce' ),
							__( 'This means that the table is probably in an inconsistent state. It\'s recommended to run a new regeneration process or to resume the aborted process (Status - Tools - Regenerate the product attributes lookup table/Resume the product attributes lookup table regeneration) before enabling the table usage.', 'woocommerce' )
						) : null;

				$settings[] = array(
					'title'         => __( 'Enable table usage', 'woocommerce' ),
					'desc'          => __( 'Use the product attributes lookup table for catalog filtering.', 'woocommerce' ),
					'desc_tip'      => $regeneration_aborted_warning,
					'id'            => 'woocommerce_attribute_lookup_enabled',
					'default'       => 'no',
					'type'          => 'checkbox',
					'checkboxgroup' => 'start',
				);

				$settings[] = array(
					'title'         => __( 'Direct updates', 'woocommerce' ),
					'desc'          => __( 'Update the table directly upon product changes, instead of scheduling a deferred update.', 'woocommerce' ),
					'id'            => 'woocommerce_attribute_lookup_direct_updates',
					'default'       => 'no',
					'type'          => 'checkbox',
					'checkboxgroup' => 'start',
				);

				$settings[] = array(
					'title'         => __( 'Optimized updates', 'woocommerce' ),
					'desc'          => __( 'Uses much more performant queries to update the lookup table, but may not be compatible with some extensions.', 'woocommerce' ),
					'desc_tip'      => __( 'This setting only works when product data is stored in the posts table.', 'woocommerce' ),
					'id'            => 'woocommerce_attribute_lookup_optimized_updates',
					'default'       => 'no',
					'type'          => 'checkbox',
					'checkboxgroup' => 'start',
				);
			}

			$settings[] = array( 'type' => 'sectionend' );
		}

		return $settings;
	}

	/**
	 * Check if the optimized database access setting is enabled.
	 *
	 * @return bool True if the optimized database access setting is enabled.
	 */
	public function optimized_data_access_is_enabled() {
		return 'yes' === get_option( 'woocommerce_attribute_lookup_optimized_updates' );
	}

	/**
	 * Create the lookup table data for a product or variation using optimized database access.
	 * For variable products entries are created for the main product and for all the variations.
	 *
	 * @param int $product_id Product or variation id.
	 */
	private function create_data_for_product_cpt( int $product_id ) {
		$this->last_create_operation_failed = false;

		try {
			$this->create_data_for_product_cpt_core( $product_id );
		} catch ( \Exception $e ) {
			$data = array(
				'source'     => 'palt-updates',
				'product_id' => $product_id,
			);

			if ( $e instanceof \WC_Data_Exception ) {
				$data = array_merge( $data, $e->getErrorData() );
			} else {
				$data['exception'] = $e;
			}

			WC()->call_function( 'wc_get_logger' )
				->error( "Lookup data creation (optimized) failed for product $product_id: " . $e->getMessage(), $data );

			$this->last_create_operation_failed = true;
		}
	}

	/**
	 * Core version of create_data_for_product_cpt (doesn't catch exceptions).
	 *
	 * @param int $product_id Product or variation id.
	 * @return void
	 * @throws \WC_Data_Exception Wrongly serialized attribute data found, or INSERT statement failed.
	 */
	private function create_data_for_product_cpt_core( int $product_id ) {
		global $wpdb;

		// phpcs:disable WordPress.DB.PreparedSQL
		$sql = $wpdb->prepare(
			"delete from {$this->lookup_table_name} where product_or_parent_id=%d",
			$product_id
		);
		$wpdb->query( $sql );
		// phpcs:enable WordPress.DB.PreparedSQL

		// * Obtain list of product variations, together with stock statuses; also get the product type.
		// For a variation this will return just one entry, with type 'variation'.
		// Output: $product_ids_with_stock_status = associative array where 'id' is the key and values are the stock status (1 for "in stock", 0 otherwise).
		// $variation_ids = raw list of variation ids.
		// $is_variable_product = true or false.
		// $is_variation = true or false.

		$sql = $wpdb->prepare(
			"(select p.ID as id, null parent, m.meta_value as stock_status, t.name as product_type from {$wpdb->posts} p
			left join {$wpdb->postmeta} m on p.id=m.post_id and m.meta_key='_stock_status'
			left join {$wpdb->term_relationships} tr on tr.object_id=p.id
			left join {$wpdb->term_taxonomy} tt on tt.term_taxonomy_id=tr.term_taxonomy_id
			left join {$wpdb->terms} t on t.term_id=tt.term_id
			where p.post_type = 'product'
			and p.post_status in ('publish', 'draft', 'pending', 'private')
			and tt.taxonomy='product_type'
			and t.name != 'exclude-from-search'
			and p.id=%d
			limit 1)
				union
			(select p.ID as id, p.post_parent as parent, m.meta_value as stock_status, 'variation' as product_type from {$wpdb->posts} p
			left join {$wpdb->postmeta} m on p.id=m.post_id and m.meta_key='_stock_status'
			where p.post_type = 'product_variation'
			and p.post_status in ('publish', 'draft', 'pending', 'private')
			and (p.ID=%d or p.post_parent=%d));
		",
			$product_id,
			$product_id,
			$product_id
		);

		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
		$product_ids_with_stock_status = $wpdb->get_results( $sql, ARRAY_A );

		$main_product_row = array_filter( $product_ids_with_stock_status, fn( $item ) => 'variation' !== $item['product_type'] );
		$is_variation     = empty( $main_product_row );

		$main_product_id =
			$is_variation ?
			current( $product_ids_with_stock_status )['parent'] :
			$product_id;

		$is_variable_product = ! $is_variation && ( 'variable' === current( $main_product_row )['product_type'] );

		$product_ids_with_stock_status = ArrayUtil::group_by_column( $product_ids_with_stock_status, 'id', true );
		$variation_ids                 = $is_variation ? array( $product_id ) : array_keys( array_diff_key( $product_ids_with_stock_status, array( $product_id => null ) ) );
		$product_ids_with_stock_status = ArrayUtil::select( $product_ids_with_stock_status, 'stock_status' );

		$product_ids_with_stock_status = array_map( fn( $item ) => 'instock' === $item ? 1 : 0, $product_ids_with_stock_status );

		// * Obtain the list of attributes used for variations and not.
		// Output: two lists of attribute slugs, all starting with 'pa_'.

		$sql = $wpdb->prepare(
			"select meta_value from {$wpdb->postmeta} where post_id=%d and meta_key=%s",
			$main_product_id,
			'_product_attributes'
		);

		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
		$temp = $wpdb->get_var( $sql );

		if ( is_null( $temp ) ) {
			// The product has no attributes, thus there's no attributes lookup data to generate.
			return;
		}

		// phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.serialize_unserialize
		$temp = unserialize( $temp );
		if ( false === $temp ) {
			throw new \WC_Data_Exception( 0, 'The product attributes metadata row is not properly serialized' );
		}

		$temp = array_filter( $temp, fn( $item, $slug ) => StringUtil::starts_with( $slug, 'pa_' ) && '' === $item['value'], ARRAY_FILTER_USE_BOTH );

		$attributes_not_for_variations =
			$is_variation || $is_variable_product ?
			array_keys( array_filter( $temp, fn( $item ) => 0 === $item['is_variation'] ) ) :
			array_keys( $temp );

		// * Obtain the terms used for each attribute.
		// Output: $terms_used_per_attribute =
		// [
		// 'pa_...' => [
		// [
		// 'term_id' => <term id>,
		// 'attribute' => 'pa_...'
		// 'slug' => <term slug>
		// ],...
		// ],...
		// ]

		$sql = $wpdb->prepare(
			"select tt.term_id, tt.taxonomy as attribute, t.slug from {$wpdb->prefix}term_relationships tr
			join {$wpdb->term_taxonomy} tt on tt.term_taxonomy_id = tr.term_taxonomy_id
			join {$wpdb->terms} t on t.term_id=tt.term_id
			where tr.object_id=%d and taxonomy like %s;",
			$main_product_id,
			'pa_%'
		);

		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
		$terms_used_per_attribute = $wpdb->get_results( $sql, ARRAY_A );
		foreach ( $terms_used_per_attribute as &$term ) {
			$term['attribute'] = strtolower( rawurlencode( $term['attribute'] ) );
		}
		$terms_used_per_attribute = ArrayUtil::group_by_column( $terms_used_per_attribute, 'attribute' );

		// * Obtain the actual variations defined (only if variations exist).
		// Output: $variations_defined =
		// [
		// <variation id> => [
		// [
		// 'variation_id' => <variation id>,
		// 'attribute' => 'pa_...'
		// 'slug' => <term slug>
		// ],...
		// ],...
		// ]
		//
		// Note that this does NOT include "any..." attributes!

		if ( ! $is_variation && ( ! $is_variable_product || empty( $variation_ids ) ) ) {
			$variations_defined = array();
		} else {
			$sql = $wpdb->prepare(
				"select post_id as variation_id, substr(meta_key,11) as attribute, meta_value as slug from {$wpdb->postmeta}
				where post_id in (select ID from {$wpdb->posts} where (id=%d or post_parent=%d) and post_type = 'product_variation')
				and meta_key like %s
				and meta_value != ''",
				$product_id,
				$product_id,
				'attribute_pa_%'
			);
			// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
			$variations_defined = $wpdb->get_results( $sql, ARRAY_A );
			$variations_defined = ArrayUtil::group_by_column( $variations_defined, 'variation_id' );
		}

		// Now we'll fill an array with all the data rows to be inserted in the lookup table.

		$insert_data = array();

		// * Insert data for the main product

		if ( ! $is_variation ) {
			foreach ( $attributes_not_for_variations as $attribute_name ) {
				foreach ( ( $terms_used_per_attribute[ $attribute_name ] ?? array() ) as $attribute_data ) {
					$insert_data[] = array( $product_id, $main_product_id, $attribute_name, $attribute_data['term_id'], 0, $product_ids_with_stock_status[ $product_id ] );
				}
			}
		}

		// * Insert data for the variations defined

		// Remove the non-variation attributes data first.
		$terms_used_per_attribute = array_diff_key( $terms_used_per_attribute, array_flip( $attributes_not_for_variations ) );

		$used_attributes_per_variation = array();
		foreach ( $variations_defined as $variation_id => $variation_data ) {
			$used_attributes_per_variation[ $variation_id ] = array();
			foreach ( $variation_data as $variation_attribute_data ) {
				$attribute_name                                   = $variation_attribute_data['attribute'];
				$used_attributes_per_variation[ $variation_id ][] = $attribute_name;
				$term_id = current( array_filter( ( $terms_used_per_attribute[ $attribute_name ] ?? array() ), fn( $item ) => $item['slug'] === $variation_attribute_data['slug'] ) )['term_id'] ?? null;
				if ( is_null( $term_id ) ) {
					continue;
				}
				$insert_data[] = array( $variation_id, $main_product_id, $attribute_name, $term_id, 1, $product_ids_with_stock_status[ $variation_id ] ?? false );
			}
		}

		// * Insert data for variations that have "any..." attributes and at least one defined attribute

		foreach ( $used_attributes_per_variation as $variation_id => $attributes_list ) {
			$any_attributes = array_diff_key( $terms_used_per_attribute, array_flip( $attributes_list ) );
			foreach ( $any_attributes as $attributes_data ) {
				foreach ( $attributes_data as $attribute_data ) {
					$insert_data[] = array( $variation_id, $main_product_id, $attribute_data['attribute'], $attribute_data['term_id'], 1, $product_ids_with_stock_status[ $variation_id ] ?? false );
				}
			}
		}

		// * Insert data for variations that have all their attributes defined as "any..."

		$variations_with_all_any = array_keys( array_diff_key( array_flip( $variation_ids ), $used_attributes_per_variation ) );
		foreach ( $variations_with_all_any as $variation_id ) {
			foreach ( $terms_used_per_attribute as $attribute_name => $attribute_terms ) {
				foreach ( $attribute_terms as $attribute_term ) {
					$insert_data[] = array( $variation_id, $main_product_id, $attribute_name, $attribute_term['term_id'], 1, $product_ids_with_stock_status[ $variation_id ] ?? false );
				}
			}
		}

		// * We have all the data to insert, let's go and insert it.

		$insert_data_chunks = array_chunk( $insert_data, 100 );
		foreach ( $insert_data_chunks as $insert_data_chunk ) {
			$sql = 'INSERT INTO ' . $this->lookup_table_name . ' (
					  product_id,
					  product_or_parent_id,
					  taxonomy,
					  term_id,
					  is_variation_attribute,
					  in_stock)
					VALUES (';

			$values_strings = array();
			foreach ( $insert_data_chunk as $dataset ) {
				$attribute_name   = esc_sql( $dataset[2] );
				$values_strings[] = "{$dataset[0]},{$dataset[1]},'{$attribute_name}',{$dataset[3]},{$dataset[4]},{$dataset[5]}";
			}

			$sql .= implode( '),(', $values_strings ) . ')';

			// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
			$result = $wpdb->query( $sql );
			if ( false === $result ) {
				throw new \WC_Data_Exception(
					0,
					'INSERT statement failed',
					0,
					array(
						'db_error' => esc_html( $wpdb->last_error ),
						'db_query' => esc_html( $wpdb->last_query ),
					)
				);
			}
		}
	}
}