presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/metadata/DatabaseShardManager.java/DatabaseShardManager/batchSize
class DatabaseShardManager:    private static int batchSize(Connection connection)
    {
        // H2 does not return generated keys properly
        // https://github.com/h2database/h2database/issues/156
        return (connection instanceof JdbcConnection) ? 1 : 1000;
    }