I have a question about modeling a mutual
relationship. It seems basic but I can't decide, maybe it is 6
of one a half dozen of the other.
In my system any user might be friends with another user,
that means they have a reciprocal friend relationship.
It seems I have two choices for modeling it.
1. I have a table with two columns userOne and userTwo. If
John is friends with Jane there will be one row for both of
them.
2. I have a table with two columns owner and friend. If
John is friends with Jane there will be two rows, one that is
{John, Jane} and another {Jane, John}.
The first option has the advantage of saving table size.
But queries are more complex because to get John's friends I
have to JOIN friends f ON f.userA = "John" OR f.userB =
"John" (not the real query, these would be id's but you get
the idea).
In the second option the table rows would be 2x but the
queries would be simpler -- JOIN friends f ON f.owner =
"John".
There could be >1M users. Each user would have <200
friends.
Thoughts? Do I just choose one or is there a clear winner?
TIA!
