Unfortunately that error indicates the database is damaged which is usually caused by data corruption from a computer crash/powercut while the database was active although it can also be caused by faulty hardware. To attempt to fix it you can reindex your database by going to 'Database -> Database Management'. Select the affected database then click 'Housekeeping -> Reindex'. After the housekeeping is complete we recommend that you rebuild the database cache via 'Rebuild Cache -> Full Cache Rebuild' to assure your database performs as expected.
These processes can take a considerable amount of time if you have a large database and/or a slow HDD so consider running it when you're not going to be using PokerTracker 4 for a while. Make sure that your computer does not power itself off or go to sleep while it's running or you will need to run things again from the start. If the original error doesn't get fixed then you should create a new database and reimport your hands although while not recommended you can set PostgreSQL to ignore those errors by
editing the postgresql.conf file.