CODEWITHSUNDEEP
scalaslickslick-2.0
John Mullins
John Mullins

Reputation: 1101

Group By including empty rows

I want to create a query that returns all groups with users count (including empty groups)

SELECT g.id, count(relation.user_id) FROM groups g 
   FULL JOIN users2groups relation ON g.id=r.group_id 
GROUP BY g.id;

for this model:

class Users(tag: Tag) extends Table[User](tag, "users") {
   def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
   ...
}
class Groups(tag: Tag) extends Table[Group](tag, "groups") {
   def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
   ...
}

val users = TableQuery[Users]
val groups = TableQuery[Groups]

/** relation for users and group */
class Users2Groups(tag: Tag) extends Table[(Long,Long)](tag, "users2groups") {
    def userId = column[Long]("user_id")
    def groupId = column[Long]("group_id")
    def user = foreignKey("user_fk", userId, users)(_.id)
    def group = foreignKey("group_fk", groupId, groups)(_.id)
    def * = (userId, groupId)
    def ? = (userId.?, groupId.?)
    def pk = primaryKey("pk_user2group", (userId, userId))
}

This is my solution with slick:

val query = for {
    (g, rel) <-
      groups leftJoin
      users2groups on (_.id === _.groupId)
} yield (g, rel.groupId.?)

val result = query.groupBy(_._1.id).map(e => (e._1, e._2.length)).list

result foreach println

But it doesn't work correctly. It returns the incorrect amount of users for empty groups (returns users count = 1 instead of 0).

My environment: scala-2.11.2, slick-2.1.0, PostgreSQL

Upvotes: 0

Views: 472

Answers (1)

cvogt
cvogt

Reputation: 11270

I don't see what's wrong. Could well be a Slick bug. Please report one here: https://github.com/slick/slick

Upvotes: 1

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