enhance: improve document

docs/en/07-develop/09-udf.md

@@ -377,7 +377,7 @@ The `pybitand` function implements bitwise addition for multiple columns. If the
 
 #### Aggregate Function [pyl2norm](https://github.com/taosdata/TDengine/blob/3.0/tests/script/sh/pyl2norm.py)
 
-The `pyl2norm` function finds the second-order norm for all data in the input column. This squares the values, takes a cumulative sum, and finds the square root.
+The `pyl2norm` function finds the second-order norm for all data in the input columns. This squares the values, takes a cumulative sum, and finds the square root.
 <details>
 <summary>pyl2norm.py</summary>
 
@@ -387,5 +387,16 @@ The `pyl2norm` function finds the second-order norm for all data in the input co
 
 </details>
 
+#### Aggregate Function [pycumsum](https://github.com/taosdata/TDengine/blob/3.0/tests/script/sh/pycumsum.py)
+
+The `pycumsum` function finds the cumulative sum for all data in the input columns.
+<details>
+<summary>pycumsum.py</summary>
+
+```c
+{{#include tests/script/sh/pycumsum.py}}
+```
+
+</details>
 ## Manage and Use UDF
 You need to add UDF to TDengine before using it in SQL queries. For more information about how to manage UDF and how to invoke UDF, please see [Manage and Use UDF](../12-taos-sql/26-udf.md).

docs/zh/07-develop/09-udf.md

@@ -335,7 +335,7 @@ def init()
 def destroy()
 ```
 
-其中 init 完成初始化工作。 destroy 完成清理工作。如果没有初始化工作，无需定义 init 函数。如果没有清理工作，无需定义 destroy 函数。
+其中 init 完成初始化工作。 destroy 完成清理工作。
 
 ### Python 和 TDengine之间的数据类型映射
 
@@ -386,6 +386,17 @@ pyl2norm 实现了输入列的所有数据的二阶范数，即对每个数据
 
 </details>
 
+### 聚合函数示例 [pycumsum](https://github.com/taosdata/TDengine/blob/3.0/tests/script/sh/pycumsum.py)
+
+pycumsum 使用 numpy 计算输入列所有数据的累积和。
+<details>
+<summary>pycumsum.py</summary>
+
+```c
+{{#include tests/script/sh/pycumsum.py}}
+```
+
+</details>
 ## 管理和使用 UDF
 在使用 UDF 之前需要先将其加入到 TDengine 系统中。关于如何管理和使用 UDF，请参考[管理和使用 UDF](../12-taos-sql/26-udf.md)
 

tests/script/sh/pycumsum.py

@@ -0,0 +1,29 @@
+import pickle
+import numpy as np
+
+def init():
+    pass
+
+def destroy():
+    pass
+
+def start():
+    return pickle.dumps(0.0)
+
+def finish(buf):
+    return pickle.loads(buf)
+
+def reduce(datablock, buf):
+    (rows, cols) = datablock.shape()
+    state = pickle.loads(buf)
+    row = []
+    for i in range(rows):
+        for j in range(cols):
+            cell = datablock.data(i, j)
+            if cell is not None:
+                row.append(datablock.data(i, j))
+    if len(row) > 1:
+        new_state = np.cumsum(row)[-1]
+    else:
+        new_state = state
+    return pickle.dumps(new_state)

tests/script/tsim/query/udfpy.sim

@@ -15,6 +15,7 @@ system sh/prepare_pyudf.sh
 system mkdir -p /tmp/pyudf
 system cp sh/pybitand.py /tmp/pyudf/
 system cp sh/pyl2norm.py /tmp/pyudf/
+system cp sh/pycumsum.py /tmp/pyudf/
 system ls /tmp/pyudf
 
 sql create database udf vgroups 3;
@@ -37,6 +38,7 @@ else
 endi
 sql create function pybitand as '/tmp/pyudf/pybitand.py' outputtype int language 'python';
 sql create aggregate function pyl2norm as '/tmp/pyudf/pyl2norm.py' outputtype double bufSize 128 language 'python';
+sql create aggregate function pycumsum as '/tmp/pyudf/pycumsum.py' outputtype double bufSize 128 language 'python';
 
 sql show functions;
 if $rows != 4 then
@@ -280,6 +282,10 @@ if $data20 != 8.000000000 then
   return -1
 endi
 
+sql select pycumsum(f2) from udf.t2
+print ======= pycumsum
+print $rows $data00
+
 sql create or replace function bit_and as '/tmp/udf/libbitand.so' outputtype int
 sql select func_version from information_schema.ins_functions where name='bit_and'
 if $data00 != 1 then