Please make a system dump, or backup every Explorer repo whenever upgrading to a new major release…​

When the explorer application is started, it will check if it has to do any data migrations. If a migration requires user input, that migration is taken care of by some ui.

1.x → 2.x

After installing Explorer 2.0, you will probably have to wait a while for it to migrate "all" your old data. Once that it done, there is also a "manual" step:

Synonyms 2.0

In order for "old" synonyms to work in Explorer 2.0, Explorer needs to be told which language(s) the old synonyms where, so that it can migrate them and apply stemming at index time.

Go to the Synonyms page and edit your Thesauri. First you pick which language(s) that Thesaurus will consist of. You may add more languages later.

You may want to make an export of the thesauri folder before migrating your Thesauri…​

Whatever language(s) you have choosen are now available in the from and to language dropdowns. Once you have filled those in, you can click the [Migrate] button, and the magic will happen :) Once that’s done click the [Save] button.

Do the same with all the other Thesauri.

Your old Thesauri may have been a "jungle" of multiple languages. Each synonym has a language dropdown, so it’s easy to change language on it.