Room Android ignores @Query conditions in Dao class (Strange)

Question

I am posting this because same issue is already there on stackoverflow but no solution on this. I am using Room library for db operations. I have created data classes with @Embedded and @Relation with other tables. Now the issue is when I put join queries with multiple where conditions on main as well as joined tables, it returns all/incorrect data of joined tables. This shows it ignores the conditions I have put in a DAO class query. Important thing is when I run the same query on a database externally (using stetho in chrome) it works as expected. Please help me with this as this is highly critical issue. Room version: 2.4.0

This is the data class:

data class ProductFull{
    @Embedded val product: ProductMaster,

    @Relation(
        entity = ProductZone::class,
        parentColumn = "productId",
        entityColumn = "productId",
    )
    var productZone: ProductZone? = null,
}

This is the DAO class method:

@Query("select * from ProductMaster as pm inner join ProductZone as pz on pz.productId = pm.productId where pz.zoneId = 3")
    abstract suspend fun getTempProducts(): List<ProductFull>

Above query returns data in productZone field of data class having zoneId = 1. Whereas it should only return zones having zoneId = 3.

Answer 1

When using @Relation room builds the underlying query(ies) to get ALL children (ProductZones) from the parents (ProductMaster) that the query selects.

A convenience annotation which can be used in a POJO to automatically fetch relation entities. When the POJO is returned from a query, all of its relations are also fetched by Room . https://developer.android.com/reference/kotlin/androidx/room/Relation

A get-around is two have 2 dao's one that selects the parents and the other that selects the required children and a function (use an abstract class rather than an interface for the Dao's) that gets the parents and then for each parent gets the required children.