HappenLee commented on code in PR #21147:
URL: https://github.com/apache/doris/pull/21147#discussion_r1241178796
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docs/zh-CN/docs/sql-manual/sql-reference/Data-Types/AGG_STATE.md:
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@@ -0,0 +1,61 @@
+---
+{
+ "title": "AGG_STATE",
+ "language": "zh-CN"
+}
+---
+
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+## AGG_STATE
+### description
+ AGG_STATE
+ AGG_STATE不能作为key列使用，建表时需要同时声明聚合函数的签名。
+ 用户不需要指定长度和默认值。实际存储的数据大小与函数实现有关。
+
+ AGG_STATE只能配合[state](../../sql-functions/combinators/state.md)
+
/[merge](../../sql-functions/combinators/merge.md)/[union](../..//sql-functions/combinators/union.md)函数组合器使用。
+
+
需要注意的是，聚合函数的签名也是类型的一部分，不同签名的agg_state无法混合使用。比如如果建表声明的签名为`max_by(int,int)`,那就无法插入`max_by(bigint,int)`或者`group_concat(varchar)`。
+ 此处nullable属性也是签名的一部分，如果能确定不会输入null值，可以将参数声明为not
null，这样可以获得更小的存储大小和减少序列化/反序列化开销。
+
+### example
+
+建表示例如下：
+
+ create table a_table(
+ k1 int null,
+ k2 agg_state max_by(int not null,int)
+ )
+ aggregate key (k1)
+ distributed BY hash(k1) buckets 3
+ properties("replication_num" = "1");
+
+插入数据示例：
+
+ insert into a_table values(1,max_by_state(3,1));
+
+查询数据示例：
+
+ select k1,max_by_merge(k2) from a_table group by k1 order by k1;
+
Review Comment:
add same real case
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