Github user rmetzger commented on a diff in the pull request:
https://github.com/apache/flink/pull/4211#discussion_r124589466
--- Diff: docs/dev/migration.md ---
@@ -25,6 +25,62 @@ under the License.
* This will be replaced by the TOC
{:toc}
+## Migrating from Flink 1.2 to Flink 1.3
+
+There are a few APIs that have been changed since Flink 1.2. Most of the
changes are documented in their
+specific documentations. The following is a consolidated list of API
changes and links to details for migration when
+upgrading to Flink 1.3.
+
+### `TypeSerializer` interface changes
+
+This would be relevant mostly for users implementing custom
`TypeSerializer`s for their state.
+
+Since Flink 1.3, two additional methods have been added that are related
to serializer compatibility
+across savepoint restores. Please see
+[Handling serializer upgrades and
compatibility](../stream/state.html#handling-serializer-upgrades-and-compatibility)
+for further details on how to implement these methods.
+
+### `ProcessFunction` is always a `RichFunction`
+
+In Flink 1.2, `ProcessFunction` and its rich variant `RichProcessFunction`
was introduced.
+Since Flink 1.3, `RichProcessFunction` was removed and `ProcessFunction`
is now always a `RichFunction` with access to
+the lifecycle methods and runtime context.
+
+### Flink CEP library API changes
+
+The CEP library in Flink 1.3 ships with a number of new features which
have led to some changes in the API.
+Please visit the [CEP Migration
docs](../libs/cep.html#migrating-from-an-older-flink-version) for details.
+
+### Table API Changes
+
+*TBA*
+
+### Queryable State client construction changes
+
+*TBA*
--- End diff --
I don't think these TBA sections are a good idea in the documentation.
Maybe we should comment them out before committing them, so that they don't
show up in the page
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