Use "utf8mb4_0900_ai_ci" as the default collation, as MySQL 8+ does

Author: JanJakes

wp-includes/sqlite-ast/class-wp-sqlite-configurator.php

@@ -147,6 +147,7 @@ public function ensure_schemata_data(): void {
 				VALUES (?, ?, ?) ON CONFLICT(SCHEMA_NAME) DO NOTHING',
 				$this->driver->get_connection()->quote_identifier( $schemata_table )
 			),
+			// The "INFORMATION_SCHEMA" database stays on "utf8mb3" even in MySQL 8 and 9.
 			array( 'information_schema', 'utf8mb3', 'utf8mb3_general_ci' )
 		);
 
@@ -190,6 +191,8 @@ public function ensure_schemata_data(): void {
 				'INSERT INTO %s (SCHEMA_NAME, DEFAULT_CHARACTER_SET_NAME, DEFAULT_COLLATION_NAME) VALUES (?, ?, ?)',
 				$this->driver->get_connection()->quote_identifier( $schemata_table )
 			),
+			// @TODO: This should probably be version-dependent.
+			//        Before MySQL 8, the default was different.
 			array( $db_name, 'utf8mb4', 'utf8mb4_0900_ai_ci' )
 		);
 	}

wp-includes/sqlite-ast/class-wp-sqlite-information-schema-builder.php

@@ -232,7 +232,8 @@ class WP_SQLite_Information_Schema_Builder {
 		'utf16le'  => 'utf16le_general_ci',
 		'utf32'    => 'utf32_general_ci',
 		'utf8'     => 'utf8_general_ci',
-		'utf8mb4'  => 'utf8mb4_general_ci', // @TODO: From MySQL 8.0.1, this is utf8mb4_0900_ai_ci.
+		'utf8mb4'  => 'utf8mb4_0900_ai_ci', // @TODO: This should probably be version-dependent.
+											//        Before MySQL 8, the default was different.
 	);
 
 	/**