twalthr commented on a change in pull request #16871:
URL: https://github.com/apache/flink/pull/16871#discussion_r700774083
##########
File path: docs/content/docs/dev/table/data_stream_api.md
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@@ -337,6 +324,86 @@ In particular, the section discusses how to influence the
schema derivation with
types. It covers working with event-time and watermarks. It discusses how to
declare a primary key and
changelog mode for the input and output streams.
+The example above shows how the final result is computed incrementally by
continuously emitting row-wise
+updates for each incoming record. However, in cases where the input streams
are finite (i.e. *bounded*),
+a result can be computed more efficiently by leveraging batch processing
principles. Both DataStream
+API and Table API offer a specialized *batch runtime mode*.
+
+The following example illustrates that the unified pipeline is able to process
both batch and streaming data
+by just switching a flag.
+
+{{< tabs "61a8a0b8-c38b-48f3-b52e-563546139380" >}}
+{{< tab "Java" >}}
+```java
+import org.apache.flink.api.common.RuntimeExecutionMode;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
+
+// setup DataStream API
+StreamExecutionEnvironment env =
StreamExecutionEnvironment.getExecutionEnvironment();
+
+// set the batch runtime mode
+env.setRuntimeMode(RuntimeExecutionMode.BATCH);
+
+// uncomment this for streaming mode
+// env.setRuntimeMode(RuntimeExecutionMode.STREAMING);
+
+// setup Table API
+// the table environment adopts the runtime mode during initialization
+StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env);
+
+// define the same pipeline as above
+
+// prints in BATCH mode:
+// +I[Bob, 10]
+// +I[Alice, 112]
+
+// prints in STREAMING mode:
+// +I[Alice, 12]
+// +I[Bob, 10]
+// -U[Alice, 12]
+// +U[Alice, 112]
Review comment:
I would leave it as a code comment here because this is only a page for
integration with DataStream API. I don't want to cover all details about how
changelog processing works. This should be a dedicated page that requires a lot
of thought. Also what switching to batch mode means actually belongs on a
different "concepts" page, but I briefly explained it here to have at least
something.
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