Android 新列的房间自动迁移不起作用

Question

I have searched stackoverflow for a similar question and none has been found, other possible solutions for different cases did not work for me either. I am opening this question seeing that I cannot find a solution for this problem, nor can I find a similar question for this problem.

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I've tried to use Android Room's auto migration feature, but it never works correctly.

The current scenario is as follows:

I have a Database version 1

I want to add a new column to one table, that is the only modification I want to do. This column will be holding String values and nothing else.

This new column will only exist in Database version 2

I have set up the Database as per the Android documentation

When I run the app again (an app with a database version 1 populated with data) the app crashes

The crash error in the console is this:

2021-08-24 21:35:53.941 3081-3141/com.app.test E/AndroidRuntime: FATAL EXCEPTION: pool-18-thread-2
    Process: com.app.test, PID: 3081
    java.lang.IllegalStateException: Migration didn't properly handle: My(com.com.app.test.data.datbase.entity.MyEntity).
     Expected:
    TableInfo{name='My', columns=long list of column definitions}
     Found:
2021-08-24 21:35:53.942 3081-3141/com.app.test E/AndroidRuntime: TableInfo{name='My', columns=long list of column definitions, plus the new one}

I have setup the database with the new version number (2), and set export schema to true, and defined the automigrations from 1 to 2.

I also defined the schemaLocation in the app gradle configuration options.

I cannot find anywhere explained why this is not working, it is a simple operation of adding a new column to an existing table.

Does anyone know why this isn't working and how can I get it to work without having to write the migration manually?

EDIT: Upon closer inspection it seems that there is some issue with the defaultValue definition in the database migration.

The expected shows the column with a default value that is not null, this is correct defaultValue=''NOT_NOTIFIED''

The found shows it is null, this is incorrect defaultValue='NULL'

The column definition for that entity is as follows

@ColumnInfo(name = "notified", defaultValue = "NOT_NOTIFIED")
public String notified = "NOT_NOTIFIED";

But somehow it is generating a definition or migration where the default value is null, instead of what I am setting it to.

Answer 1

Removing the defaultValue from the column definition in the entity itself appears to do the trick, but it is a requirement to have a default value for that column. This does not appear to be a proper behavior, but a bug somewhere in the auto migration logic.

Hoping someone might have a clue of what is going on and come up with a proper solution that is not to remove the defaultValue definition.

Answer 2

I've had the same issue lately, and for me, the issue was that I forgot about a manual migration I've written a while ago that had the same version numbers.

This might not be your case, but for me to figure out why I was getting the wrong migration, I set a breakpoint at the onUpgrade method at RoomOpenHelper.java which led me to the forgotten manual migration. so give it a try it might provide you with more information on what's going on.

Answer 3

Specifying the columnInfo name and default value did the trick for me