presto-spi/src/main/java/io/prestosql/spi/block/SingleMapBlock.java/SingleMapBlock/getSizeInBytes
class SingleMapBlock:    @Override
    public long getSizeInBytes()
    {
        return mapBlock.getRawKeyBlock().getRegionSizeInBytes(offset / 2, positionCount / 2) +
                mapBlock.getRawValueBlock().getRegionSizeInBytes(offset / 2, positionCount / 2) +
                sizeOfIntArray(positionCount / 2 * HASH_MULTIPLIER);
    }