presto-main/src/main/java/io/prestosql/operator/JoinHash.java/JoinHash/getInMemorySizeInBytes
class JoinHash:    @Override
    public long getInMemorySizeInBytes()
    {
        return INSTANCE_SIZE + pagesHash.getInMemorySizeInBytes() + (positionLinks == null ? 0 : positionLinks.getSizeInBytes());
    }