> you have to actually add the columns That's easy. Renaming, splitting, changing data types, or altering character encodings... on in-use production data? Tha

> you have to actually add the columns That's easy. Renaming, splitting, changing data types, or altering character encodings... on in-use production data? That's harder, and you may need to take downtime. On the other hand, document-oriented databases allow in-stream data model changes. More code, of course, but with care you can spread the cost of the upgrade over time. I'm not a huge advocate for document-oriented databases, but there are trade-offs.