presto-main/src/main/java/io/prestosql/util/JsonUtil.java/DoubleJsonGeneratorWriter/writeJsonValue
class DoubleJsonGeneratorWriter:        @Override
        public void writeJsonValue(JsonGenerator jsonGenerator, Block block, int position, ConnectorSession session)
                throws IOException
        {
            if (block.isNull(position)) {
                jsonGenerator.writeNull();
            }
            else {
                double value = DOUBLE.getDouble(block, position);
                jsonGenerator.writeNumber(value);
            }
        }