SweepPress is a powerful plugin, and it can do a lot to clean up your WordPress-powered website database, but this is a plugin that removes data from the database, so you should make sure to understand properly how to use it, what the best way is to use the plugin, and maintain your database.
Before you go on, make sure to go through the plugin user guide and follow articles about various plugin features. The list of recommendations listed here will be expanded over time, so make sure to check out this article from time to time to get the latest in best usage practices.
Here is the list of general recommendations for using the SweepPress:
Make sure you have regular database backups in case you remove some data that you later want to get back. SweepPress doesn’t back up your data and can’t restore it once it is removed! Database backup is up to you!
Do not run the Database Optimizer sweeper too often; once every few months is enough. This sweeper runs server-intensive operations that can also take more time to finish; they can even recreate the table and copy the data to ensure it is optimized.
Make sure to read all the information provided for each sweeper to understand it better. Each sweeper has a lot of information provided on the plugin Sweep panel, including limitations and a list of affected database tables.
Plugin uses elaborate SQL queries to determine and estimate what needs to be removed. All these estimations are just that: estimations, and they are not 100% precise. For an actual number of affected/removed records, the size of the data may differ from real results, and the difference can be in the range of -20% to +20%. Plugin queries are adjusted with every update to make the estimation process better.
Having 100% correct size and records calculated is impossible without removing the data and calculating the difference, so the estimation is the best that can be achieved.