What does Room return if a query had no results

Question

Having a difficult time finding this answer and the documentation doesn't seem to answer the question. If I have a basic ROOM query,

@Query("SELECT * FROM geotable WHERE geohash = :geohash")
abstract suspend fun getGeoTable(geohash: String) : GeoTable

and there is no such item that uses this primary key, what happens? Android studio says that the DAO object will never return a null. It seems that EmptyResultSetException only gets thrown when you have Single using RxJava which I am not using. So what does plain old ROOM throw when it finds nothing?

Answer 1

Based on the documentation a fruitless query's behavior is defined by the declared return type:

1. fun func(foo: Foo): Bar would throw a EmptyResultSetException
2. fun func(foo: Foo): Bar? would return null
3. fun func(foo: Foo): List<Bar> would return an empty list

Answer 2

If nothing is found based on your criteria, it will return null.