presto-spi/src/main/java/io/prestosql/spi/block/MapBlockBuilder.java/MapBlockBuilder/getSizeInBytes
class MapBlockBuilder:    @Override
    public long getSizeInBytes()
    {
        return keyBlockBuilder.getSizeInBytes() + valueBlockBuilder.getSizeInBytes() +
                (Integer.BYTES + Byte.BYTES) * (long) positionCount +
                Integer.BYTES * HASH_MULTIPLIER * (long) keyBlockBuilder.getPositionCount();
    }