lsyldliu commented on code in PR #21789:
URL: https://github.com/apache/flink/pull/21789#discussion_r1098208433
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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 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.
Review Comment:
Fixed.
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