在数据库中保存友谊。 社交网络服务

Question

At present, I am currently storing in this way in the database

id  from_id  to_id
1     1        2
2     2        1

I write down such friendships in this way

this.friendshipRepository.save(new FriendshipEntity(fromUser.get(), toUser.get()));
this.friendshipRepository.save(new FriendshipEntity(toUser.get(), fromUser.get()));

a when I remove

this.friendshipRepository.delete(this.friendshipRepository.findOneByFromUserAndToUser(fromUser.get(), toUser.get()));
this.friendshipRepository.delete(this.friendshipRepository.findOneByFromUserAndToUser(toUser.get(), fromUser.get()));

I have to do everything twice. It is a little inconvenient.

Do you know any better ways to store friendship between users in the database?

Answer 1

if you consider friendship is symmetric, then an option is to rewrite your database schema. instead of

id  from_id  to_id

it could be

id  lower_id  higher_id

so a given friendship has a unique entry in the database, and you can remove a friendship with a single query.

the downside is that if you want to list someone friends, you have to look up this someone in both lower_id and higher_id