short tips on doing migration mobile development using room DB

SQLite migration room db - android

this process (mgration) is a vital step need to defined very serious.
after setup library room db on android you need to make sure to export schema everytime it changes.
see mine here:
---
build.gradle (app)
---
defaultConfig {
  //schema provide for DB room
  javaCompileOptions {
      annotationProcessorOptions {
          arguments = ["room.schemaLocation": "$projectDir/schemas".toString()]
      }
  }
}

//in case need to test migration DB
sourceSets {
    androidTest.assets.srcDirs += files("$projectDir/schemas".toString())
}

dependencies {
  //db room
  implementation "androidx.room:room-runtime:$roomVersion"
  annotationProcessor "androidx.room:room-compiler:$roomVersion"
}

----
@Database(
  entities = {class_with_field.class}
  version = init_version(ex. 1),
  autoMigrations = {
    @AutoMigration(
      from = current_version_which_init_version
      to = upgrade_to_version_what_number
    )
  },
  exportSchema = true
)
public abstract DBApp extends RoomDatabase {
  //room db builder
  Room.databasebuilder(context, class_db.class, name_db_string)
    .addMigrations(here_add_migration_operation_upgrade)
}
---

- done with setup and ready to upgrade version db, run first for current db version number to generate schemas.json file
- the file gonna generate with format db_number.json
- but before upgrade to latest version, I assume you are doing the first trial to upgrade.
- so you need to commenting in the section `automigration` with version DB not upgraded yet to latest version (ex. current in version 1, wanna upgrade to version 2. So you need to stay still on version 1)
- after file.json generated on schema folder. You ready to upgrade version by commenting out the automigration section and increase version db
- system will generate file.json (ex. latest_version_ex_2.json) and doing upgrade.
- dont forget to add on git
- every time upgrade crashed, see log cat !!