presto-spi/src/main/java/io/prestosql/spi/block/VariableWidthBlockBuilder.java/VariableWidthBlockBuilder/getSizeInBytes
class VariableWidthBlockBuilder:    @Override
    public long getSizeInBytes()
    {
        long arraysSizeInBytes = (Integer.BYTES + Byte.BYTES) * (long) positions;
        return sliceOutput.size() + arraysSizeInBytes;
    }