presto-spi/src/main/java/io/prestosql/spi/block/VariableWidthBlockBuilder.java/VariableWidthBlockBuilder/retainedBytesForEachPart
class VariableWidthBlockBuilder:    @Override
    public void retainedBytesForEachPart(BiConsumer<Object, Long> consumer)
    {
        consumer.accept(sliceOutput, sliceOutput.getRetainedSize());
        consumer.accept(offsets, sizeOf(offsets));
        consumer.accept(valueIsNull, sizeOf(valueIsNull));
        consumer.accept(this, (long) INSTANCE_SIZE);
    }