Github user tzulitai commented on a diff in the pull request:
https://github.com/apache/flink/pull/4041#discussion_r119607645
--- Diff: docs/dev/libs/cep.md ---
@@ -659,37 +913,45 @@ val patternStream: PatternStream[Event] =
CEP.pattern(input, pattern)
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+The input stream can be *keyed* or *non-keyed* depending on your use-case.
+
+<span class="label label-danger">Attention</span> Applying your pattern on
a non-keyed stream will result is a job with
+parallelism equal to 1.
+
### Selecting from Patterns
+
Once you have obtained a `PatternStream` you can select from detected
event sequences via the `select` or `flatSelect` methods.
<div class="codetabs" markdown="1">
<div data-lang="java" markdown="1">
The `select` method requires a `PatternSelectFunction` implementation.
A `PatternSelectFunction` has a `select` method which is called for each
matching event sequence.
-It receives a map of string/event pairs of the matched events.
-The string is defined by the name of the state to which the event has been
matched.
-The `select` method can return exactly one result.
+It receives a match in the form of `Map<String, List<IN>>` where the key
is the name of each state in your pattern
+sequence and the value is a list of all accepted events for that state
(`IN` is the type of your input elements).
--- End diff --
Perhaps add information about the ordering of the list of matched events?
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