Upgrade/Install: Indicate use of MyISAM storage engine in upgrade check.

In MySQL 5.5.5, the default storage engine was changed from `MyISAM` to `InnoDB`. While still available, usage of `MyISAM` has been discouraged since and is considered legacy due to the lack of support for more modern feature. 

The percentage of WordPress sites with `MyISAM` tables in the wild is currently unknown. This change adds a field to upgrade checks that includes a list of tables using `MyISAM` to help make more informed decisions about database features in the future.

Props johnjamesjacoby, johnbillion, dd32, desrosj, mukesh27.
Fixes #63640.

git-svn-id: https://develop.svn.wordpress.org/trunk@61001 602fd350-edb4-49c9-b593-d223f7449a82

Author: desrosj

src/wp-includes/update.php

@@ -106,6 +106,7 @@ function wp_version_check( $extra_stats = array(), $force_check = false ) {
 		'users'              => get_user_count(),
 		'multisite_enabled'  => $multisite_enabled,
 		'initial_db_version' => get_site_option( 'initial_db_version' ),
+		'myisam_tables'      => array(),
 		'extensions'         => array_combine( $extensions, array_map( 'phpversion', $extensions ) ),
 		'platform_flags'     => array(
 			'os'   => PHP_OS,
@@ -114,6 +115,39 @@ function wp_version_check( $extra_stats = array(), $force_check = false ) {
 		'image_support'      => array(),
 	);
 
+	// Check for default tables using the MyISAM engine.
+	$table_names   = implode( "','", $wpdb->tables() );
+	$myisam_tables = $wpdb->get_results(
+		$wpdb->prepare(
+			// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- This query cannot use interpolation.
+			"SELECT TABLE_NAME FROM information_schema.TABLES WHERE TABLE_SCHEMA = %s AND TABLE_NAME IN ('$table_names') AND ENGINE = %s;",
+			DB_NAME,
+			'MyISAM'
+		),
+		OBJECT_K
+	);
+
+	if ( ! empty( $myisam_tables ) ) {
+		$all_unprefixed_tables = $wpdb->tables( 'all', false );
+
+		// Including the table prefix is not necessary.
+		$unprefixed_myisam_tables = array_reduce(
+			array_keys( $myisam_tables ),
+			function ( $carry, $prefixed_myisam_table ) use ( $all_unprefixed_tables ) {
+				foreach ( $all_unprefixed_tables as $unprefixed ) {
+					if ( str_ends_with( $prefixed_myisam_table, $unprefixed ) ) {
+						$carry[] = $unprefixed;
+						break;
+					}
+				}
+				return $carry;
+			},
+			array()
+		);
+
+		$query['myisam_tables'] = $unprefixed_myisam_tables;
+	}
+
 	if ( function_exists( 'gd_info' ) ) {
 		$gd_info = gd_info();
 		// Filter to supported values.