[GitHub] [flink] luoyuxia commented on a diff in pull request #21789: [FLINK-30824][hive] Add document for option table.exec.hive.native-agg-function.enabled

["luoyuxia (via GitHub)" <gi...@apache.org>]

luoyuxia commented on code in PR #21789:
URL: https://github.com/apache/flink/pull/21789#discussion_r1097303357


##########
docs/content.zh/docs/connectors/table/hive/hive_functions.md:
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@@ -73,6 +73,34 @@ Some Hive built-in functions in older versions have [thread safety issues](https
 We recommend users patch their own Hive to fix them.
 {{< /hint >}}
 
+## Use Native Hive Aggregate Functions
+
+If [HiveModule]({{< ref "docs/dev/table/modules" >}}#hivemodule) is loaded with a higher priority than CoreModule, Flink will try to use the Hive built-in function first. And then for Hive built-in aggregation function,
+Flink currently uses sort-based aggregation strategy. Compared to hash-based aggregation strategy, the performance is one to two times worse, so from Flink 1.17, we have implemented some of Hive's aggregation functions natively in Flink.
+These functions will use the hash-agg strategy to improve performance. Currently, only five functions are supported, namely sum/count/avg/min/max, and more aggregation functions will be supported in the future.
+Users can use the native aggregation function by turning on the option `table.exec.hive.native-agg-function.enabled`, which brings significant performance improvement to the job.
+
+<table class="table table-bordered">
+  <thead>
+    <tr>
+        <th class="text-left" style="width: 20%">Key</th>
+        <th class="text-left" style="width: 15%">Default</th>
+        <th class="text-left" style="width: 10%">Type</th>
+        <th class="text-left" style="width: 55%">Description</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+        <td><h5>table.exec.hive.native-agg-function.enabled</h5></td>
+        <td style="word-wrap: break-word;">false</td>
+        <td>Boolean</td>
+        <td>Enabling to use native aggregate function which use hash-agg strategy that can improve the aggregation performance after loading HiveModule. This is a job-level option, user can enable it per-job.</td>
+    </tr>
+  </tbody>
+</table>
+
+<span class="label label-danger">Attention</span> The ability of the native aggregate function implementation does not fully align with Hive built-in aggregation function now, for example some data types are not supported. If performance is not a bottleneck, you don't need to turn on this option.

Review Comment:
   ```suggestion
   <span class="label label-danger">Attention</span> The ability of the native aggregate functions don't fully align with Hive built-in aggregation functions now, for example, some data types are not supported. If performance is not a bottleneck, you don't need to turn on this option.
   ```



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