Add a note on query builder behaviour change

README.md

@@ -86,6 +86,39 @@ go run _examples/booktown-books/main.go
 2016/08/10 08:42:48 "Practical PostgreSQL" (ID: 41472)
 ```
 
+## Changeog
+
+Dec 15th, 2016: Before `2.0.0-rc8`, upper-db produced queries that mutated
+themselves:
+
+```
+q := sess.SelectFrom("users")
+
+q.Where(...) // This method modified q's internal state.
+```
+
+Starting on `2.0.0-rc8` this is no longer valid, if you want to use values to
+represent queries you'll have to reassign them, like this:
+
+```
+q := sess.SelectFrom("users")
+
+q = q.Where(...)
+
+q.And(...) // Nothing happens, the Where() method does not affect q.
+```
+
+This applies to all query builder methods, `db.Result`, `db.And` and `db.Or`.
+
+If you want to check your code for statatements that might rely on the old
+behaviour and could cause you trouble use `dbcheck`:
+
+```
+go get -u github.com/upper/cmd/dbcheck
+
+dbcheck github.com/my/package/...
+```
+
 ## License
 
 This project is licensed under the terms of the **MIT License**.