Feature request: Allow to provide a "TypeAdapter" for collections [69164099]

Fixed

Bug

Status Update

No update yet.

Description

de...@gmail.com

created issue #1

Nov 10, 2017 06:53PM

Component used: Room
Version used: 1.0
Devices/Android versions reproduced on: NA

I have one entity that contains a set of enums. For example:

@Entity
data class Person(
@field:PrimaryKey val id: Int,
val name: String,
val favouriteDays: Set<Day>)

enum class Day {
MONDAY,
TUESDAY,
WEDNESDAY,
THURSDAY,
FRIDAY,
SATURDAY,
SUNDAY
}

I want to store this entity in a single table. In many cases, especially with enums, we could use a single bit mask to save the list as a number in the database.

Here's one example of what I wanted to do:

object DayCollectionTypeConverter {
@JvmStatic
@TypeConverter
fun daysConverter(days: Set<Day>): Int {
var value = 0
for (day in days) {
value += (1 shl day.ordinal)
}
return value
}

@JvmStatic
@TypeConverter
fun daysConverter(value: Int): Set<Day> {
val set = mutableSetOf<Day>()
for (day in Day.values()) {
if (value and 1 shl day.ordinal != 0) {
set.add(day)
}
}
return set
}
}

That code doesn't work as intended because @TypeConverter would allow me to convert one Day object, but not a collection (or set, list, etc) of Days.

I suggest a new annotation is created so the developer can specify how to save a Collection into a single column in the same table.

Comments

fs...@gmail.com <fs...@gmail.com> #2Nov 11, 2017 12:03AM

we've considered this, just didn't have time to implement.

Btw, we cannot just use name() because it might be proguarded away. so we need to generate the code that matches enums to hardcoded string values.

If you are using name(), be careful about migrations since 2 different compilations might have different names for the enum values.

yb...@google.com <yb...@google.com> #3Nov 27, 2017 08:24PM

True. Even though this could be fixed by using proguard rules.

Would be great to see this in the future, it's really lots of code here ;)

de...@gmail.com <de...@gmail.com> #4Nov 27, 2017 09:50PM

What about the idea of using a more generic adapter which can handle all of the enums in your app? That way you could decide to persist them all with one "stone". You could choose to save them as strings, ordinals or even some other way of your choosing. But you would not have to add an adapter for every enum type in your app. You just have to add the one special enum adapter and Room would know how to use it for all enums.

Poc.kt

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yb...@google.com <yb...@google.com> #5Dec 15, 2017 09:39PM

This seems like a possible candidate for external contributions so moving it to the bug bounty hotlist.

We still need a proper design here hence not super straightforward.

Such design should ensure we are:

safe for proguard (in case we go w/ name)
have some logic for defaults (in case an enum is removed or renamed)
possibly support ordinals (though that might be a case where we can require a type converter)
possibly make it opt-in so that developer explicitly picks an option (e.g. some annotation on the enum to enable this)

yb...@google.com <yb...@google.com> #6Dec 18, 2017 09:29PM

Status: Assigned (reopened)

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

commit ae093dec7bfdc578cf0d7cd2ee6c8563ddd4f5ed
Author: Elif Bilgin <elifbilgin@google.com>
Date: Wed Oct 21 11:50:07 2020

Optimization for storing enums in databases.

Creating a default type adapter to persist Enums in Room. Changes made in logic of the findQueryParameterAdapter(...) function where we now try to find a TypeConverter for the collection of an object first, and if not, then try to find one for the type arg.

Test: Baseline tests replicate compiler errors in EnumColumnTypeAdapterTest.java
Bug: 73132006
Change-Id: Ia212097c16fde4302bc7c20cbad1604a996090ad

M room/compiler-processing/src/main/java/androidx/room/compiler/processing/XType.kt
M room/compiler-processing/src/main/java/androidx/room/compiler/processing/javac/JavacType.kt
M room/compiler-processing/src/main/java/androidx/room/compiler/processing/ksp/KspArrayType.kt
M room/compiler-processing/src/main/java/androidx/room/compiler/processing/ksp/KspDeclaredType.kt
M room/compiler-processing/src/main/java/androidx/room/compiler/processing/ksp/KspType.kt
M room/compiler-processing/src/main/java/androidx/room/compiler/processing/ksp/KspTypeArgumentType.kt
M room/compiler/src/main/kotlin/androidx/room/solver/TypeAdapterStore.kt
A room/compiler/src/main/kotlin/androidx/room/solver/types/EnumColumnTypeAdapter.kt
M room/compiler/src/test/kotlin/androidx/room/processor/DaoProcessorTest.kt
M room/compiler/src/test/kotlin/androidx/room/solver/TypeAdapterStoreTest.kt
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/test/EnumColumnTypeAdapterTest.java

https://android-review.googlesource.com/1469447

yb...@google.com <yb...@google.com> #7Dec 18, 2017 10:17PM

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

commit ed8d4acdb13cba24fcb1a392b36952ddfe790776
Author: Elif Bilgin <elifbilgin@google.com>
Date: Wed Oct 21 11:50:07 2020

Optimization for storing enums in databases.

Creating a default type adapter to persist Enums in Room. Changes made in logic of the findQueryParameterAdapter(...) function where we now try to find a TypeConverter for the collection of an object first, and if not, then try to find one for the type arg.

Test: Baseline tests replicate compiler errors in EnumColumnTypeAdapterTest.java
Bug: 73132006
Change-Id: I4cfa8c7f9ac3dc97ec4591ceef6f97b4cba7a6ad

M room/compiler-processing/src/main/java/androidx/room/compiler/processing/XType.kt
M room/compiler-processing/src/main/java/androidx/room/compiler/processing/javac/JavacType.kt
M room/compiler-processing/src/main/java/androidx/room/compiler/processing/ksp/KspType.kt
M room/compiler/src/main/kotlin/androidx/room/solver/TypeAdapterStore.kt
A room/compiler/src/main/kotlin/androidx/room/solver/types/EnumColumnTypeAdapter.kt
M room/compiler/src/test/kotlin/androidx/room/processor/DaoProcessorTest.kt
M room/compiler/src/test/kotlin/androidx/room/solver/TypeAdapterStoreTest.kt
A room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/test/EnumColumnTypeAdapterTest.java

https://android-review.googlesource.com/1500819

yb...@google.com <yb...@google.com> Dec 19, 2017 11:43PM

Marked as fixed.