presto-spi/src/main/java/io/prestosql/spi/block/SingleMapBlockWriter.java/SingleMapBlockWriter/getRetainedSizeInBytes
class SingleMapBlockWriter:    @Override
    public long getRetainedSizeInBytes()
    {
        return INSTANCE_SIZE + keyBlockBuilder.getRetainedSizeInBytes() + valueBlockBuilder.getRetainedSizeInBytes();
    }