Upgrading from Objectbox v1.5 to v2.x fails with index on unsupported property

Issue Basics

• ObjectBox version: 1.5 upgrading to 2.x (2.3.4 at time of writing)
• Reproducibility: always

Reproducing the bug

Create project with objectbox v1.5, define Object with Entity.

@Entity
public class Foo {
@Index private Double Lat;
@Index private Double Lng;
}

Compile and run project, in order to create the objectbox DB and save some instances.

Update the objectbox version in the project to 2.3.4, then update the entity by removing the @Index annotations

Update the entity to
@Entity
public class Foo {
private Double Lat;
private Double Lng;
}

Recompile and run project again. You will get the following Exception:

io.objectbox.exception.DbException: Indexing of float and double is currently unavailable. Please remove the index on Property Lat (5, Double)

Description

This bug has been already mentioned and discussed in the StackOverflow Thread https://stackoverflow.com/questions/54149954/double-field-index-problem-when-upgrading-objectbox-library

Upgrading the objectbox instance from 1.5 to 2.x when having an @Index set on a Double field is impossible for existing apps.

A desired way of handling this would be to remove the @Index from the existing legacy data structure internally and let the app keep the data as before, making a migration to the new objectbox version possible and seamless.

Please fix this issue as an upgrade of the module is impossible.

Code

ObjectBox v1.5

@Entity
public class Foo {
@Index private Double Lat;
@Index private Double Lng;
}

ObjectBox v2.3.4
@Entity
public class Foo {
private Double Lat;
private Double Lng;
}

triggers runtime DbException: "io.objectbox.exception.DbException: Indexing of float and double is currently unavailable. Please remove the index on Property Lat (5, Double)"

Logs & stackstraces

io.objectbox.exception.DbException: Indexing of float and double is currently unavailable. Please remove the index on Property Lat (5, Double)

Misc

Is there anything special about your app?
No

May transactions or multi-threading play a role?
No

Did you find any workarounds to prevent the issue?
No workarounds found to date

Start with the Java reproduction described in the issue: create a v1.5 database with indexed Double fields, then upgrade to ObjectBox 2.3.4 after removing the annotations. Trace the migration handling for the legacy index that triggers the DbException; done means the existing database opens successfully without the obsolete index and retains its data.