IssueTracker

Hi there - so the core issue here is coming from the fact that because this is a JOIN with identical column names in different tables, Room is unable to differentiate between which column value is coming from which table. Therefore it is null-check'ing the wrong column.

We are currently working on a fix to handle identical column names in Room therefore this issue will be resolved once that is done. Until then, is it possible to use unique column names to resolve this issue?

You can follow the progress of the duplicate column bug linked below under "blocking by".

Project: platform/frameworks/support
Branch: androidx-main

commit 894b0ff2c1b095a46803975f400a561eb974ea28
Author: Daniel Santiago Rivera <danysantiago@google.com>
Date:   Fri Oct 29 10:56:31 2021

    Duplicate column resolution heuristic algorithm
   
    AmbiguousColumnResolver contains an algorithm to map query result columns to data objects (POJOs) columns. We call data object columns 'mapping' and in a multimap query where there might be multiple data objects we refer to the list of all their columns 'mappings'. The algorithm uses a grouping / neighboring strategy to assign the duplicate columns to their right data objects matching their name along with taking into account the the nearby columns since in a star-projected query all columns coming from a table will appear in the result before the next table. Room will generate code that uses the algorithm at runtime if the query has a star-projection, if not then Room will use the algorithm during compile-time since the columns result order is known and fixed.
   
    The algorithm does not solve all cases, specifically those where one of the data objects has a single column which is the duplicate column. For those situation Room will warn the user so that they alias the duplicate column. For other odd cases, Room will behave as it used to, picking the first result column that matches with the data object column.
   
    Bug: 201306012
    Bug: 212279118
    Test: AmbiguousColumnResolverTest
    Relnote: Room will now attempt to resolve ambiguous columns in a multimap query. This allows for JOINs with tables containing same-name tables to be correctly mapped to a result data object.
    Change-Id: I4b444b042245a334cc3f362f3239721ce0b6bd1e

M       room/room-compiler/src/main/kotlin/androidx/room/solver/query/result/EntityRowAdapter.kt
M       room/room-compiler/src/main/kotlin/androidx/room/solver/TypeAdapterStore.kt
A       room/integration-tests/kotlintestapp/src/androidTest/java/androidx/room/integration/kotlintestapp/test/AmbiguousColumnResolverTest.kt
M       room/room-compiler/src/main/kotlin/androidx/room/solver/query/result/PojoRowAdapter.kt
M       room/room-common/api/current.txt
M       room/room-compiler/src/main/kotlin/androidx/room/vo/Warning.kt
M       room/room-runtime/api/restricted_current.txt
A       room/room-common/src/main/java/androidx/room/AmbiguousColumnResolver.kt
M       room/room-common/api/public_plus_experimental_current.txt
M       room/room-common/build.gradle
M       room/room-compiler/src/main/kotlin/androidx/room/processor/ProcessorErrors.kt
M       room/room-common/src/main/java/androidx/room/RoomWarnings.kt
M       room/room-compiler/src/main/kotlin/androidx/room/solver/query/result/MultimapQueryResultAdapter.kt
M       room/room-compiler/src/main/kotlin/androidx/room/solver/query/result/GuavaImmutableMultimapQueryResultAdapter.kt
M       room/room-runtime/src/main/java/androidx/room/util/CursorUtil.kt
M       room/room-compiler/src/main/kotlin/androidx/room/ext/javapoet_ext.kt
A       room/room-compiler/src/main/kotlin/androidx/room/solver/query/result/AmbiguousColumnIndexAdapter.kt
M       room/room-compiler/src/test/kotlin/androidx/room/processor/QueryMethodProcessorTest.kt
M       room/room-compiler/src/main/kotlin/androidx/room/solver/query/result/ImmutableMapQueryResultAdapter.kt
A       room/room-common/src/test/java/androidx/room/AmbiguousColumnResolverTest.kt
M       room/room-compiler/src/main/kotlin/androidx/room/solver/query/result/MapQueryResultAdapter.kt
M       room/room-common/api/restricted_current.txt

https://android-review.googlesource.com/2064298