A developer asks:
It is known whether performance suffers by exposing too many columns? We want to expose an additional 20 to 30 properties as individual columns in one of our database tables, mostly for reporting purpose. Do you have a recommendation for the maximum number of columns that should be exposed?
Exposing properties as database columns is in general a good idea, and the 20 to 30 additional columns that you propose are not likely to create a noticeable performance issue. (Exposing properties as database columns creates copies of the properties in the Blob column; it does not delete them from the Blob.)
Anecdotally, having too many columns means that each database row becomes big and your database suffers additional processing and space overhead: The more exposed columns, and the more native database indexes you have, the more expensive the each read, update, or delete operation becomes.
Consider involving a DBA who is familiar with of the fine art of database tuning. Going overboard by exposing hundreds of properties is probably excessive. But significant performance degradation is unlikely with 20 to 30 new columns.