presto-spi/src/main/java/io/prestosql/spi/block/SingleRowBlockWriter.java/SingleRowBlockWriter/getFieldBlockBuilder
class SingleRowBlockWriter:    public BlockBuilder getFieldBlockBuilder(int fieldIndex)
    {
        if (currentFieldIndexToWrite != 0) {
            throw new IllegalStateException("field block builder can only be obtained before any sequential write has done");
        }
        fieldBlockBuilderReturned = true;
        return fieldBlockBuilders[fieldIndex];
    }