This is a document for PGroonga 1.X. See PGroonga 2.x document when you're using recent PGroonga.
pgroonga_check moduleSince 1.2.0.
pgroonga_check module checkes PGroonga database consistency on startup. If PGroonga database is broken, it tries to recover the database.
You need to add pgroonga_check to shared_preload_libraries in postgresql.conf:
shared_preload_libraries = 'pgroonga_check'
You need to restart your PostgreSQL to apply the change.
You don't do anything. pgroonga_check module checks all PGroonga databases on PostgreSQL startup. If pgroonga_check module finds any broken PGroonga databases, it tries to recover them automatically.
If it can't recover, it removes all unrecoverable PGroonga databases automatically. There are no unrecoverable data in PGroonga databases. You can recover PGroonga databases by running REINDEX manually.