Log all db errors and exceptions in the posts to orders migrators.

To achieve this:

- A new class is added, TableMigrator, containing basic in-memory
  error storage methods, and auxiliary db_query and db_get_result
  methods.
- MetaToCustomTableMigrator and MetaToMetaTableMigrator classes
  now extend TableMigrator and use these db_* methods.
- process_migration_batch_for_ids is now a method in TableMigrator,
  it just calls the abstract process_migration_batch_for_ids_core,
  catches exceptions, and returns an array of errors.
- PostsToOrdersMigrationController now logs all the errors returned
  by process_migration_batch_for_ids in all the migrator classes.
- New utility method: ArrayUtil::to_ranges_string

plugins/woocommerce/src/Database/Migrations/CustomOrderTable/MetaToCustomTableMigrator.php

@@ -13,7 +13,7 @@ use Automattic\WooCommerce\Database\Migrations\MigrationHelper;
  *
  * @package Automattic\WooCommerce\Database\Migrations\CustomOrderTable
  */
-abstract class MetaToCustomTableMigrator {
+abstract class MetaToCustomTableMigrator extends TableMigrator {
 
 	/**
 	 * Config for tables being migrated and migrated from. See __construct() for detailed config.
@@ -36,13 +36,6 @@ abstract class MetaToCustomTableMigrator {
 	 */
 	protected $core_column_mapping;
 
-	/**
-	 * Store errors along with entity IDs from migrations.
-	 *
-	 * @var array
-	 */
-	protected $errors;
-
 	/**
 	 * MetaToCustomTableMigrator constructor.
 	 */
@@ -50,7 +43,6 @@ abstract class MetaToCustomTableMigrator {
 		$this->schema_config       = MigrationHelper::escape_schema_for_backtick( $this->get_schema_config() );
 		$this->meta_column_mapping = $this->get_meta_column_config();
 		$this->core_column_mapping = $this->get_core_column_mapping();
-		$this->errors              = array();
 	}
 
 	/**
@@ -224,13 +216,13 @@ abstract class MetaToCustomTableMigrator {
 	}
 
 	/**
-	 * Process next migration batch, uses option `wc_cot_migration` to checkpoints of what have been processed so far.
+	 * Migrate a batch of orders from the posts table to the corresponding table.
 	 *
-	 * @param array $entity_ids List of entity IDs to perform migrations for.
+	 * @param array $entity_ids Ids of orders ro migrate.
 	 *
-	 * @return array List of errors happened during migration.
+	 * @return void
 	 */
-	public function process_migration_batch_for_ids( array $entity_ids ): array {
+	protected function process_migration_batch_for_ids_core( array $entity_ids ): void {
 		$data = $this->fetch_data_for_migration_for_ids( $entity_ids );
 
 		foreach ( $data['errors'] as $entity_id => $errors ) {
@@ -240,7 +232,7 @@ abstract class MetaToCustomTableMigrator {
 		}
 
 		if ( count( $data['data'] ) === 0 ) {
-			return array();
+			return;
 		}
 
 		$entity_ids       = array_keys( $data['data'] );
@@ -251,10 +243,6 @@ abstract class MetaToCustomTableMigrator {
 
 		$to_update = array_intersect_key( $data['data'], $already_migrated );
 		$this->process_update_batch( $to_update, $already_migrated );
-
-		return array(
-			'errors' => $this->errors,
-		);
 	}
 
 	/**
@@ -263,18 +251,15 @@ abstract class MetaToCustomTableMigrator {
 	 * @param array $batch Data to insert, will be of the form as returned by `data` in `fetch_data_for_migration_for_ids`.
 	 */
 	private function process_insert_batch( array $batch ): void {
-		global $wpdb;
 		if ( 0 === count( $batch ) ) {
 			return;
 		}
 
 		$queries = $this->generate_insert_sql_for_batch( $batch );
 		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- Queries should already be prepared.
-		$result = $wpdb->query( $queries );
+		$actual_processed_count = $this->db_query( $queries );
-		$wpdb->query( 'COMMIT;' ); // For some reason, this seems necessary on some hosts? Maybe a MySQL configuration?
+		$this->db_query( 'COMMIT;' ); // For some reason, this seems necessary on some hosts? Maybe a MySQL configuration?
-		if ( count( $batch ) !== $result ) {
+		$this->maybe_add_insert_or_update_mismatch_error( 'insert', $batch, $actual_processed_count );
-			$this->errors[] = 'Error with batch: ' . $wpdb->last_error;
-		}
 	}
 
 	/**
@@ -284,18 +269,15 @@ abstract class MetaToCustomTableMigrator {
 	 * @param array $already_migrated Maps rows to update data with their original IDs.
 	 */
 	private function process_update_batch( array $batch, array $already_migrated ): void {
-		global $wpdb;
 		if ( 0 === count( $batch ) ) {
 			return;
 		}
 
 		$queries = $this->generate_update_sql_for_batch( $batch, $already_migrated );
 		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- Queries should already be prepared.
-		$result = $wpdb->query( $queries );
+		$actual_processed_count = $this->db_query( $queries );
-		$wpdb->query( 'COMMIT;' ); // For some reason, this seems necessary on some hosts? Maybe a MySQL configuration?
+		$this->db_query( 'COMMIT;' ); // For some reason, this seems necessary on some hosts? Maybe a MySQL configuration?
-		if ( count( $batch ) !== $result ) {
+		$this->maybe_add_insert_or_update_mismatch_error( 'update', $batch, $actual_processed_count );
-			$this->errors[] = 'Error with batch: ' . $wpdb->last_error;
-		}
 	}
 
 
@@ -316,8 +298,6 @@ abstract class MetaToCustomTableMigrator {
 	 * )
 	 */
 	private function fetch_data_for_migration_for_ids( array $entity_ids ): array {
-		global $wpdb;
-
 		if ( empty( $entity_ids ) ) {
 			return array(
 				'data'   => array(),
@@ -327,7 +307,7 @@ abstract class MetaToCustomTableMigrator {
 
 		$entity_table_query = $this->build_entity_table_query( $entity_ids );
 		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- Output of $this->build_entity_table_query is already prepared.
-		$entity_data = $wpdb->get_results( $entity_table_query );
+		$entity_data = $this->db_get_results( $entity_table_query );
 		if ( empty( $entity_data ) ) {
 			return array(
 				'data'   => array(),
@@ -338,7 +318,7 @@ abstract class MetaToCustomTableMigrator {
 
 		$meta_table_query = $this->build_meta_data_query( $entity_meta_rel_ids );
 		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- Output of $this->build_meta_data_query is already prepared.
-		$meta_data = $wpdb->get_results( $meta_table_query );
+		$meta_data = $this->db_get_results( $meta_table_query );
 
 		return $this->process_and_sanitize_data( $entity_data, $meta_data );
 	}
@@ -370,7 +350,7 @@ abstract class MetaToCustomTableMigrator {
 
 		$entity_id_placeholder = implode( ',', array_fill( 0, count( $entity_ids ), '%d' ) );
 
-		$already_migrated_entity_ids = $wpdb->get_results(
+		$already_migrated_entity_ids = $this->db_get_results(
 			$wpdb->prepare(
 				// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare -- All columns and table names are hardcoded.
 				"

plugins/woocommerce/src/Database/Migrations/CustomOrderTable/MetaToMetaTableMigrator.php

@@ -13,7 +13,7 @@ use Automattic\WooCommerce\Database\Migrations\MigrationHelper;
  *
  * @package Automattic\WooCommerce\Database\Migrations\CustomOrderTable
  */
-abstract class MetaToMetaTableMigrator {
+abstract class MetaToMetaTableMigrator extends TableMigrator {
 
 	/**
 	 * Schema config, see __construct for more details.
@@ -22,13 +22,6 @@ abstract class MetaToMetaTableMigrator {
 	 */
 	private $schema_config;
 
-	/**
-	 * Store errors along with entity IDs from migrations.
-	 *
-	 * @var array
-	 */
-	protected $errors;
-
 	/**
 	 * Returns config for the migration.
 	 *
@@ -67,40 +60,35 @@ abstract class MetaToMetaTableMigrator {
 	 */
 	public function __construct() {
 		$this->schema_config = $this->get_meta_config();
-		$this->errors        = array();
 	}
 
 	/**
-	 * Process migration for provided entity ids.
+	 * Migrate a batch of orders from the posts table to the corresponding table.
 	 *
-	 * @param array $entity_ids Entity IDs to process migration for.
+	 * @param array $entity_ids Ids of orders ro migrate.
 	 */
-	public function process_migration_batch_for_ids( array $entity_ids ): void {
+	protected function process_migration_batch_for_ids_core( array $entity_ids ): void {
-		global $wpdb;
 		$to_migrate = $this->fetch_data_for_migration_for_ids( $entity_ids );
 
-		$already_migrated = $this->get_already_migrated_records( array_keys( $to_migrate['data'] ) );
+		$already_migrated = $this->get_already_migrated_records( array_keys( $to_migrate ) );
 
-		$data      = $this->classify_update_insert_records( $to_migrate['data'], $already_migrated );
+		$data      = $this->classify_update_insert_records( $to_migrate, $already_migrated );
 		$to_insert = $data[0];
 		$to_update = $data[1];
 
 		if ( ! empty( $to_insert ) ) {
-			$insert_queries = $this->generate_insert_sql_for_batch( $to_insert );
+			$insert_queries         = $this->generate_insert_sql_for_batch( $to_insert );
-			// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- $insert_queries should already be escaped in the generating function.
+			$actual_processed_count = $this->db_query( $insert_queries );
-			$result = $wpdb->query( $insert_queries );
+			$this->db_query( 'COMMIT;' );
-			$wpdb->query( 'COMMIT;' );
+			$this->maybe_add_insert_or_update_mismatch_error( 'insert', $to_insert, $actual_processed_count );
-			// TODO: Find and log entity ids that were not inserted.
 		}
 
-		if ( empty( $to_update ) ) {
+		if ( ! empty( $to_update ) ) {
-			return;
+			$update_queries         = $this->generate_update_sql_for_batch( $to_update );
+			$actual_processed_count = $this->db_query( $update_queries );
+			$this->db_query( 'COMMIT;' );
+			$this->maybe_add_insert_or_update_mismatch_error( 'update', $to_insert, $actual_processed_count );
 		}
-		$update_queries = $this->generate_update_sql_for_batch( $to_update );
-		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- update queries are autogenerated and should already be prepared.
-		$result = $wpdb->query( $update_queries );
-		$wpdb->query( 'COMMIT;' );
-		// TODO: Find and log error updates.
 	}
 
 	/**
@@ -186,34 +174,22 @@ abstract class MetaToMetaTableMigrator {
 	 *
 	 * @param array $entity_ids Array of IDs to fetch data for.
 	 *
-	 * @return array[] Data along with errors (if any), will of the form:
+	 * @return array[] Data, will of the form:
 	 * array(
-	 *  'data' => array(
+	 *   'id_1' => array( 'column1' => value1, 'column2' => value2, ...),
-	 *      'id_1' => array( 'column1' => value1, 'column2' => value2, ...),
+	 *   ...,
-	 *      ...,
-	 *   ),
-	 *  'errors' => array(
-	 *      ...,
 	 * )
 	 */
-	public function fetch_data_for_migration_for_ids( array $entity_ids ): array {
+	private function fetch_data_for_migration_for_ids( array $entity_ids ): array {
-		global $wpdb;
 		if ( empty( $entity_ids ) ) {
-			return array(
+			return array();
-				'data'   => array(),
-				'errors' => array(),
-			);
 		}
 
 		$meta_query = $this->build_meta_table_query( $entity_ids );
 
-		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- Meta query has interpolated variables, but they should all be escaped for backticks.
+		$meta_data_rows = $this->db_get_results( $meta_query );
-		$meta_data_rows = $wpdb->get_results( $meta_query );
 		if ( empty( $meta_data_rows ) ) {
-			return array(
+			return array();
-				'data'   => array(),
-				'errors' => array(),
-			);
 		}
 
 		foreach ( $meta_data_rows as $migrate_row ) {
@@ -229,10 +205,7 @@ abstract class MetaToMetaTableMigrator {
 			$to_migrate[ $migrate_row->entity_id ][ $migrate_row->meta_key ][] = $migrate_row->meta_value;
 		}
 
-		return array(
+		return $to_migrate;
-			'data'   => $to_migrate,
-			'errors' => array(),
-		);
 	}
 
 	/**
@@ -254,8 +227,8 @@ abstract class MetaToMetaTableMigrator {
 		$entity_id_type_placeholder = MigrationHelper::get_wpdb_placeholder_for_type( $this->schema_config['destination']['meta']['entity_id_type'] );
 		$entity_ids_placeholder     = implode( ',', array_fill( 0, count( $entity_ids ), $entity_id_type_placeholder ) );
 
-		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- All columns are hardcoded.
+		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare
-		$data_already_migrated = $wpdb->get_results(
+		$data_already_migrated = $this->db_get_results(
 			$wpdb->prepare(
 				"
 SELECT

plugins/woocommerce/src/Database/Migrations/CustomOrderTable/PostsToOrdersMigrationController.php

@@ -6,6 +6,7 @@
 namespace Automattic\WooCommerce\Database\Migrations\CustomOrderTable;
 
 use Automattic\WooCommerce\Database\Migrations\MigrationErrorLogger;
+use Automattic\WooCommerce\Utilities\ArrayUtil;
 
 /**
  * This is the main class used to perform the complete migration of orders
@@ -18,62 +19,47 @@ class PostsToOrdersMigrationController {
 	/**
 	 * Error logger for migration errors.
 	 *
-	 * @var MigrationErrorLogger $error_logger
+	 * @var WC_Logger
 	 */
 	private $error_logger;
 
 	/**
-	 * Migrator instance to migrate data into wc_order table.
+	 * Array of objects used to perform the migration.
 	 *
-	 * @var PostToOrderTableMigrator
+	 * @var array
 	 */
-	private $order_table_migrator;
+	private $all_migrators;
 
 	/**
-	 * Migrator instance to migrate billing data into address table.
+	 * The source name to use for logs.
-	 *
-	 * @var PostToOrderAddressTableMigrator
 	 */
-	private $billing_address_table_migrator;
+	private const LOGS_SOURCE_NAME = 'posts-to-orders-migration';
-
-	/**
-	 * Migrator instance to migrate shipping data into address table.
-	 *
-	 * @var PostToOrderAddressTableMigrator
-	 */
-	private $shipping_address_table_migrator;
-
-	/**
-	 * Migrator instance to migrate operational data.
-	 *
-	 * @var PostToOrderOpTableMigrator
-	 */
-	private $operation_data_table_migrator;
-
-	/**
-	 * Migrator instance to migrate meta data.
-	 *
-	 * @var MetaToMetaTableMigrator
-	 */
-	private $meta_table_migrator;
 
 	/**
 	 * PostsToOrdersMigrationController constructor.
 	 */
 	public function __construct() {
 
-		$this->order_table_migrator            = new PostToOrderTableMigrator();
+		$order_table_migrator            = new PostToOrderTableMigrator();
-		$this->billing_address_table_migrator  = new PostToOrderAddressTableMigrator( 'billing' );
+		$billing_address_table_migrator  = new PostToOrderAddressTableMigrator( 'billing' );
-		$this->shipping_address_table_migrator = new PostToOrderAddressTableMigrator( 'shipping' );
+		$shipping_address_table_migrator = new PostToOrderAddressTableMigrator( 'shipping' );
-		$this->operation_data_table_migrator   = new PostToOrderOpTableMigrator();
+		$operation_data_table_migrator   = new PostToOrderOpTableMigrator();
 
-		$excluded_columns = array_keys( $this->order_table_migrator->get_meta_column_config() );
+		$excluded_columns    = array_keys( $order_table_migrator->get_meta_column_config() );
-		$excluded_columns = array_merge( $excluded_columns, array_keys( $this->billing_address_table_migrator->get_meta_column_config() ) );
+		$excluded_columns    = array_merge( $excluded_columns, array_keys( $billing_address_table_migrator->get_meta_column_config() ) );
-		$excluded_columns = array_merge( $excluded_columns, array_keys( $this->shipping_address_table_migrator->get_meta_column_config() ) );
+		$excluded_columns    = array_merge( $excluded_columns, array_keys( $shipping_address_table_migrator->get_meta_column_config() ) );
-		$excluded_columns = array_merge( $excluded_columns, array_keys( $this->operation_data_table_migrator->get_meta_column_config() ) );
+		$excluded_columns    = array_merge( $excluded_columns, array_keys( $operation_data_table_migrator->get_meta_column_config() ) );
+		$meta_table_migrator = new PostMetaToOrderMetaMigrator( $excluded_columns );
 
-		$this->meta_table_migrator             = new PostMetaToOrderMetaMigrator( $excluded_columns );
+		$this->all_migrators = array(
-		$this->error_logger                    = new MigrationErrorLogger();
+			$order_table_migrator,
+			$billing_address_table_migrator,
+			$shipping_address_table_migrator,
+			$operation_data_table_migrator,
+			$meta_table_migrator,
+		);
+
+		$this->error_logger = wc_get_logger();
 	}
 
 	/**
@@ -82,12 +68,53 @@ class PostsToOrdersMigrationController {
 	 * @param array $order_post_ids List of post IDs of the orders to migrate.
 	 */
 	public function migrate_orders( array $order_post_ids ): void {
-		$this->order_table_migrator->process_migration_batch_for_ids( $order_post_ids );
+		foreach ( $this->all_migrators as $migrator ) {
-		$this->billing_address_table_migrator->process_migration_batch_for_ids( $order_post_ids );
+			$this->do_orders_migration_step( $migrator, $order_post_ids );
-		$this->shipping_address_table_migrator->process_migration_batch_for_ids( $order_post_ids );
+		}
-		$this->operation_data_table_migrator->process_migration_batch_for_ids( $order_post_ids );
+	}
-		$this->meta_table_migrator->process_migration_batch_for_ids( $order_post_ids );
+
-		// TODO: Return merged error array.
+	/**
+	 * Performs one step of the migration for a set of order posts using one given migration class.
+	 * All database errors and exceptions are logged.
+	 *
+	 * @param object $migration_class The migration class to use, must have a `process_migration_batch_for_ids(array of ids)` method.
+	 * @param array  $order_post_ids List of post IDs of the orders to migrate.
+	 * @return void
+	 */
+	private function do_orders_migration_step( object $migration_class, array $order_post_ids ): void {
+		$result = $migration_class->process_migration_batch_for_ids( $order_post_ids );
+
+		$errors    = $result['errors'];
+		$exception = $result['exception'];
+		if ( null === $exception && empty( $errors ) ) {
+			return;
+		}
+
+		$migration_class_name = ( new \ReflectionClass( $migration_class ) )->getShortName();
+		$batch                = ArrayUtil::to_ranges_string( $order_post_ids );
+
+		if ( null !== $exception ) {
+			$exception_class = get_class( $exception );
+			$this->error_logger->error(
+				"$migration_class_name: when processing ids $batch: ($exception_class) {$exception->getMessage()}, {$exception->getTraceAsString()}",
+				array(
+					'source'    => self::LOGS_SOURCE_NAME,
+					'ids'       => $order_post_ids,
+					'exception' => $exception,
+				)
+			);
+		}
+
+		foreach ( $errors as $error ) {
+			$this->error_logger->error(
+				"$migration_class_name: when processing ids $batch: $error",
+				array(
+					'source'    => self::LOGS_SOURCE_NAME,
+					'ids'       => $order_post_ids,
+					'exception' => $exception,
+				)
+			);
+		}
 	}
 
 	/**
@@ -97,6 +124,5 @@ class PostsToOrdersMigrationController {
 	 */
 	public function migrate_order( int $order_post_id ): void {
 		$this->migrate_orders( array( $order_post_id ) );
-		// TODO: Return error.
 	}
 }

plugins/woocommerce/src/Database/Migrations/CustomOrderTable/TableMigrator.php

@@ -0,0 +1,140 @@
+<?php
+/**
+ * Base class for all the WP posts to order table migrator.
+ */
+
+namespace Automattic\WooCommerce\Database\Migrations\CustomOrderTable;
+
+/**
+ * Base class for implementing WP posts to order tables migrations handlers.
+ * It mainly contains methods to deal with error handling.
+ *
+ * @package Automattic\WooCommerce\Database\Migrations\CustomOrderTable
+ */
+abstract class TableMigrator {
+
+	/**
+	 * An array of cummulated error messages.
+	 *
+	 * @var array
+	 */
+	private $errors;
+
+	/**
+	 * Clear the error messages list.
+	 *
+	 * @return void
+	 */
+	protected function clear_errors(): void {
+		$this->errors = array();
+	}
+
+	/**
+	 * Add an error message to the errors list unless it's there already.
+	 *
+	 * @param string $error The error message to add.
+	 * @return void
+	 */
+	protected function add_error( string $error ): void {
+		if ( ! in_array( $error, $this->errors, true ) ) {
+			$this->errors[] = $error;
+		}
+	}
+
+	/**
+	 * Get the list of error messages added.
+	 *
+	 * @return array
+	 */
+	protected function get_errors(): array {
+		return $this->errors;
+	}
+
+	/**
+	 * Run $wpdb->query and add the error, if any, to the errors list.
+	 *
+	 * @param string $query The SQL query to run.
+	 * @return mixed Whatever $wpdb->query returns.
+	 */
+	protected function db_query( string $query ) {
+		global $wpdb;
+
+		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
+		$result = $wpdb->query( $query );
+
+		if ( '' !== $wpdb->last_error ) {
+			$this->add_error( $wpdb->last_error );
+		}
+
+		return $result;
+	}
+
+	/**
+	 * Run $wpdb->get_results and add the error, if any, to the errors list.
+	 *
+	 * @param string|null $query The SQL query to run.
+	 * @param string      $output Any of ARRAY_A | ARRAY_N | OBJECT | OBJECT_K constants.
+	 * @return mixed Whatever $wpdb->get_results returns.
+	 */
+	protected function db_get_results( string $query = null, string $output = OBJECT ) {
+		global $wpdb;
+
+		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
+		$result = $wpdb->get_results( $query, $output );
+
+		if ( '' !== $wpdb->last_error ) {
+			$this->add_error( $wpdb->last_error );
+		}
+
+		return $result;
+	}
+
+	/**
+	 * Migrate a batch of orders, logging any database error that could arise and the exception thrown if any.
+	 *
+	 * @param array $entity_ids Order ids to migrate.
+	 * @return array An array containing the keys 'errors' (array of strings) and 'exception' (exception object or null).
+	 */
+	public function process_migration_batch_for_ids( array $entity_ids ): array {
+		$this->clear_errors();
+		$exception = null;
+
+		try {
+			$this->process_migration_batch_for_ids_core( $entity_ids );
+		} catch ( \Exception $ex ) {
+			$exception = $ex;
+		}
+
+		return array(
+			'errors'    => $this->get_errors(),
+			'exception' => $exception,
+		);
+	}
+
+	/**
+	 * The core method that actually performs the migration for the supplied batch of order ids.
+	 * It doesn't need to deal with database errors nor with exceptions.
+	 *
+	 * @param array $entity_ids Order ids to migrate.
+	 * @return void
+	 */
+	abstract protected function process_migration_batch_for_ids_core( array $entity_ids ): void;
+
+	/**
+	 * Check if the amount of processed database rows matches the amount of orders to process, and log an error if not.
+	 *
+	 * @param string   $operation Operation performed, 'insert' or 'update'.
+	 * @param array    $entity_ids Order ids that were supplied for migration.
+	 * @param int|bool $actual_processed_count Count of processed database rows or boolean false, as supplied by $wpdb->get_results.
+	 * @return void
+	 */
+	protected function maybe_add_insert_or_update_mismatch_error( string $operation, array $entity_ids, $actual_processed_count ) {
+		$count = count( $entity_ids );
+
+		if ( false === $actual_processed_count ) {
+			$this->add_error( "$operation operation didn't complete, the database query failed" );
+		} elseif ( $actual_processed_count < $count ) {
+			$this->add_error( "$operation operation didn't complete for all entities. Initial batch size: $count, actual processed size: $actual_processed_count" );
+		}
+	}
+}

plugins/woocommerce/src/Utilities/ArrayUtil.php

@@ -67,5 +67,48 @@ class ArrayUtil {
 	public static function get_value_or_default( array $array, string $key, $default = null ) {
 		return isset( $array[ $key ] ) ? $array[ $key ] : $default;
 	}
+
+	/**
+	 * Converts an array of numbers to a human-readable range, such as "1,2,3,5" to "1-3, 5". It also supports
+	 * floating point numbers, however with some perhaps unexpected / undefined behaviour if used within a range.
+	 * Source: https://stackoverflow.com/a/34254663/4574
+	 *
+	 * @param array     $items    An array (in any order, see $sort) of individual numbers.
+	 * @param string    $item_separator  The string that separates sequential range groups.  Defaults to ', '.
+	 * @param string    $range_separator The string that separates ranges.  Defaults to '-'.  A plausible example otherwise would be ' to '.
+	 * @param bool|true $sort     Sort the array prior to iterating?  You'll likely always want to sort, but if not, you can set this to false.
+	 *
+	 * @return string
+	 */
+	public static function to_ranges_string( array $items, string $item_separator = ', ', string $range_separator = '-', bool $sort = true ): string {
+		if ( $sort ) {
+			sort( $items );
+		}
+
+		$point = null;
+		$range = false;
+		$str   = '';
+
+		foreach ( $items as $i ) {
+			if ( null === $point ) {
+				$str .= $i;
+			} elseif ( ( $point + 1 ) === $i ) {
+				$range = true;
+			} else {
+				if ( $range ) {
+					$str  .= $range_separator . $point;
+					$range = false;
+				}
+				$str .= $item_separator . $i;
+			}
+			$point = $i;
+		}
+
+		if ( $range ) {
+			$str .= $range_separator . $point;
+		}
+
+		return $str;
+	}
 }
 

plugins/woocommerce/tests/php/src/Utilities/ArrayUtilTest.php

@@ -134,4 +134,38 @@ class ArrayUtilTest extends \WC_Unit_Test_Case {
 
 		$this->assertEquals( 'buzz', ArrayUtil::get_value_or_default( $array, 'fizz', 'buzz' ) );
 	}
+
+	/**
+	 * Data provider for test_to_ranges_string
+	 *
+	 * @return array[]
+	 */
+	public function data_provider_for_test_to_ranges_string(): array {
+		return array(
+			array( '1', array( 1 ) ),
+			array( '1, 3, 5, 7, 9, 11, 13-15', array( 1, 3, 5, 7, 9, 11, 13, 14, 15 ) ),
+			array( '1-5', array( 1, 2, 3, 4, 5 ) ),
+			array( '7-10', array( 7, 8, 9, 10 ) ),
+			array( '1-3, 5, 7-8', array( 1, 2, 3, 5, 7, 8 ) ),
+			array( '1-5, 10-12', array( 1, 2, 3, 4, 5, 10, 11, 12 ) ),
+			array( '1-5, 7', array( 1, 2, 3, 4, 5, 7 ) ),
+			array( '10, 12-15', array( 10, 12, 13, 14, 15 ) ),
+			array( '10, 12-15, 101', array( 10, 12, 13, 14, 15, 101 ) ),
+			array( '1-5, 7, 10-12', array( 1, 2, 3, 4, 5, 7, 10, 11, 12 ) ),
+			array( '1-5, 7, 10-12, 101', array( 1, 2, 3, 4, 5, 7, 10, 11, 12, 101 ) ),
+			array( '1-5, 7, 10, 12, 14', array( 14, 12, 10, 1, 2, 3, 4, 5, 7 ) ),
+		);
+	}
+
+	/**
+	 * @testdox `to_ranges_string` works as expected with the default arguments.
+	 * @dataProvider data_provider_for_test_to_ranges_string
+	 *
+	 * @param string $expected_string The expected generated string.
+	 * @param array  $input_array The input array of numbers.
+	 */
+	public function test_to_ranges_string( string $expected_string, array $input_array ) {
+		$actual = ArrayUtil::to_ranges_string( $input_array );
+		$this->assertEquals( $expected_string, $actual );
+	}
 }