How to join multiple instances of same object in Android Room?

Question

NOTE: I cannot use relation as we had performance issue which is not reproduced on direct join query.

Until I added target user and from group use

Answer 1

In the query, you have to set an alias for the table chat_user as you are joining it twice in the same name which will confuse database engine so it tells you that the field is ambiguous.

EDIT:

I found something that may be similar to your issue: https://github.com/JetBrains/Exposed/issues/177

Also they referred to this code as an example to fix this issue:

    object Users : Table() {
        val id = varchar("id", 10).primaryKey()
        val name = varchar("name", length = 50)
        val residentialCityId = optReference("resid_city_id", Cities)
        val bornCityId = optReference("born_city_id", Cities)
    }

    object Cities : IntIdTable() {
        val name = varchar("name", 50) // Column
    }
    fun test() {
        val userTable1 = Users.alias("u1")
        val userTable2 = Users.alias("u2")

        Cities
            .innerJoin(userTable1, {Cities.id}, {userTable1[Users.residentialCityId]})
            .innerJoin(userTable2, {Cities.id}, {userTable2[Users.bornCityId]})
            .selectAll()
    }