Affect row count from insert, update and delete

**Is your feature request related to a problem? Please describe.** Some time I'd like to know how many rows changed after UPDATE statement executed, to control parallel access. e.g. SELECT id,update_time FROM TableA UPDATE TableA SET SOMETHING WHERE id=? AND update_time=? If no rows affected, the progress may retry. **Describe the solution you'd like** I was used `go-pg` for golang, each execute function (Update, Insert, Delete) may return orm.Result, I can call RowsAffected() from it. If I missed something, please let me know, thanks.