[taligent]

Schema changes are exclusively an application-layer change in MongoDB. So MongoDB can support as many schemas as you want at the same time whilst you are migrating.

Also don't forget that MongoDB can have arrays and sets as a "column" type. Which if you tried to replicate in RDBMS would mean a multi-table migration.

[jeltz]

> Schema changes are exclusively an application-layer change in MongoDB.

Which is not by itself an advantage. You still need to write the code which does the schema change if you for example rename a field.

> Also don't forget that MongoDB can have arrays and sets as a "column" type. Which if you tried to replicate in RDBMS would mean a multi-table migration.

So can PostgreSQL. The sets are not as general as in MongoDB though since they can only store strings.