Many-to-many @Relation [69201917]

Fixed

Bug

Status Update

No update yet.

Description

am...@gmail.com

created issue #1

Nov 11, 2017 09:18PM

Please add the ability to create @Relation that work through a junction table to support many-to-many relationships. They would effectively need to follow an ID relation through the paired ForeignKey.

Comments

am...@gmail.com <am...@gmail.com> #2Dec 31, 2017 01:28AM

Any feedback on this? I'm no SQL expert, so I could be going at this wrong, but I'm finding M:N in Room to be so convoluted it isn't worth it. Manual joins create a ton of redundant object models and multiple queries create some sketchy nested LiveData. Can you guys manage M:N with Room at scale or is there any work in progress?

am...@gmail.com <am...@gmail.com> #3Dec 31, 2017 09:26PM

So I finally figured something manageable out, though I suspect the onChanged observation won't work perfectly and there's probably a more efficient method:

https://gist.github.com/rcketscientist/53cbdab925fcaa7dc9850375160e023b

yb...@google.com <yb...@google.com> Sep 7, 2018 05:51PM

Assigned to da...@google.com.

ap...@google.com <ap...@google.com> #4Jun 11, 2019 09:35PM

Project: platform/frameworks/support
Branch: androidx-master-dev

commit 5c597749f35557501041bce0c62f055e5afe9d72
Author: Daniel Santiago Rivera <danysantiago@google.com>
Date: Thu May 30 11:11:21 2019

Support many-to-many with @Relation using @Junction

Expand @Relation to contain a new method, 'associateBy' of type
@Junction that can be used to specify a junction table for resolving
relationships, mainly many-to-many.

Upon using @Junction the query
generated by the RelationCollector is of the form of:
SELECT *, <junction-parent-column>
FROM <junction-table> AS _junction
JOIN <entity-table> ON (<junction-entity-column> = <entity-column>)
WHERE <junction-parent-column> IN (:args)

@Junction supports both an @Entity or @DatabaseView, the Junction table
itself doesn't have to strictly model a many-to-many relation. Both
parentColumn and entityColumn are optional and will be assumed to be
the same as the ones defined in @Relation, otherwise those methods can
be used to specify arbitrary columns in the junction table.

Room will also give a warning for those columns in the junction table
that are not part of a foreign key.

Bug: 63736353
Bug: 69201917
Test: ManyToManyRelationTest, PojoProcessorTest, and others...
Change-Id: I967cf77252391379377ebe0ebfeb23a4fd881ca5

A room/common/api/2.2.0-alpha01.ignore
M room/common/api/2.2.0-alpha01.txt
M room/common/api/current.txt
A room/common/src/main/java/androidx/room/Junction.java
M room/common/src/main/java/androidx/room/Relation.java
M room/compiler/src/main/kotlin/androidx/room/ext/element_ext.kt
M room/compiler/src/main/kotlin/androidx/room/processor/EntityProcessor.kt
M room/compiler/src/main/kotlin/androidx/room/processor/PojoProcessor.kt
M room/compiler/src/main/kotlin/androidx/room/processor/ProcessorErrors.kt
A room/compiler/src/main/kotlin/androidx/room/vo/Junction.kt
M room/compiler/src/main/kotlin/androidx/room/vo/Relation.kt
M room/compiler/src/main/kotlin/androidx/room/vo/Warning.kt
M room/compiler/src/main/kotlin/androidx/room/writer/RelationCollectorMethodWriter.kt
M room/compiler/src/test/kotlin/androidx/room/processor/PojoProcessorTest.kt
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/MusicTestDatabase.java
M room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/TestDatabase.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/dao/MusicDao.java
M room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/dao/UserDao.java
M room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/dao/UserPetDao.java
M room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/test/LiveDataQueryTest.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/test/ManyToManyRelationTest.java
M room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/test/PojoWithRelationTest.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/FriendsJunction.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/MultiSongPlaylistWithSongs.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/Playlist.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/PlaylistMultiSongXRefView.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/PlaylistSongXRef.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/PlaylistWithSongTitles.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/PlaylistWithSongs.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/UserAndAllPetsViaJunction.java
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/UserAndFriends.java

https://android-review.googlesource.com/973527

https://goto.google.com/android-sha1/5c597749f35557501041bce0c62f055e5afe9d72

da...@google.com <da...@google.com> Jun 11, 2019 10:38PM

Marked as fixed.

ap...@google.com <ap...@google.com> #5Jun 12, 2019 04:01PM

Project: platform/frameworks/support
Branch: androidx-master-dev

commit 0afda8aec8143c7dd58d0be6a5dc8a90a150cf75
Author: Daniel Santiago Rivera <danysantiago@google.com>
Date: Mon Jun 10 13:13:21 2019

Improve warning messages caused by @Relation.

1. Warn about column affinity mismatch when using a junction table.
2. Don't warn about cursor mismatch when finding an adapter for the
relation field. The query is generated by the compiler and it might
use more columns than those needed for the object (specifically the
key column), therefore force suppress the warning to avoid the noise.
3. When noting about using a Cursor adapter because the relation type
is simple, then include the field element, otherwise these messages
are printed without knowing which relation is being noted.

Bug: 63736353
Bug: 69201917
Test: ManyToManyRelationTest
Change-Id: Ie3975ac31a88296afddbab51fe48302ac2693513

M room/compiler/src/main/kotlin/androidx/room/processor/Context.kt
M room/compiler/src/main/kotlin/androidx/room/processor/ProcessorErrors.kt
M room/compiler/src/main/kotlin/androidx/room/vo/RelationCollector.kt
M room/compiler/src/main/kotlin/androidx/room/writer/RelationCollectorMethodWriter.kt
M room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/vo/PlaylistSongXRef.java

https://android-review.googlesource.com/980058

https://goto.google.com/android-sha1/0afda8aec8143c7dd58d0be6a5dc8a90a150cf75

Issue 69201917