Database upgrade takes minutes and explodes in size.

[sync-by-unito]

A Realm Java user has reported an issue with an upgrade from version 7.0.8 (core
6.1.3) to version 10.4.0 (core 10.5.6).

Such upgrade takes from 5 to 10 minutes to be processed on his db. He shared a demo database where we can replicate the issue. 

I have noticed on this demo database that not only it takes a great amount of time, but the size of the db also explodes by 7x its initial size. This space can later be reclaimed by doing compaction-on-launch.

How come is that this migration takes that amount of time, and how come that the database is left uncompacted after the migration?

[jedelbo]

This comes from the fact that we removed the search indexes for the primary key columns and because of that had to rebuild the tables. This is unfortunately a rather slow process. We are now working on re-introducing the indexes.
Assigning to @finnschiermer

[sync-by-unito]

➤ Finn Andersen commented:

Should be fixed in Core release v11.0.0-beta.6