diff --git a/core/java/android/database/sqlite/SQLiteOpenHelper.java b/core/java/android/database/sqlite/SQLiteOpenHelper.java index 33418006330c4..5e523c0112b1b 100644 --- a/core/java/android/database/sqlite/SQLiteOpenHelper.java +++ b/core/java/android/database/sqlite/SQLiteOpenHelper.java @@ -513,6 +513,19 @@ public abstract class SQLiteOpenHelper implements AutoCloseable { * This method executes within a transaction. If an exception is thrown, all changes * will automatically be rolled back. *

+ *

+ * Important: You should NOT modify an existing migration step from version X to X+1 + * once a build has been released containing that migration step. If a migration step has an + * error and it runs on a device, the step will NOT re-run itself in the future if a fix is made + * to the migration step.

+ *

For example, suppose a migration step renames a database column from {@code foo} to + * {@code bar} when the name should have been {@code baz}. If that migration step is released + * in a build and runs on a user's device, the column will be renamed to {@code bar}. If the + * developer subsequently edits this same migration step to change the name to {@code baz} as + * intended, the user devices which have already run this step will still have the name + * {@code bar}. Instead, a NEW migration step should be created to correct the error and rename + * {@code bar} to {@code baz}, ensuring the error is corrected on devices which have already run + * the migration step with the error.

* * @param db The database. * @param oldVersion The old database version.