diff --git a/src/.vuepress/sidebar/V2.0.x/en-Table.ts b/src/.vuepress/sidebar/V2.0.x/en-Table.ts
index 6a97f9bb7..0eba127da 100644
--- a/src/.vuepress/sidebar/V2.0.x/en-Table.ts
+++ b/src/.vuepress/sidebar/V2.0.x/en-Table.ts
@@ -93,6 +93,7 @@ export const enSidebar = {
       prefix: 'User-Manual/',
       children: [
         { text: 'Data Sync', link: 'Data-Sync_apache' },
+        { text: 'UDF', link: 'User-defined-function' },
         {
           text: 'Security Permissions',
           collapsible: true,
diff --git a/src/.vuepress/sidebar/V2.0.x/zh-Table.ts b/src/.vuepress/sidebar/V2.0.x/zh-Table.ts
index 742a53121..5206d54dd 100644
--- a/src/.vuepress/sidebar/V2.0.x/zh-Table.ts
+++ b/src/.vuepress/sidebar/V2.0.x/zh-Table.ts
@@ -86,6 +86,7 @@ export const zhSidebar = {
       prefix: 'User-Manual/',
       children: [
         { text: '数据同步', link: 'Data-Sync_apache' },
+        { text: '用户自定义函数', link: 'User-defined-function' },
         {
           text: '安全权限',
           collapsible: true,
diff --git a/src/.vuepress/sidebar_timecho/V2.0.x/en-Table.ts b/src/.vuepress/sidebar_timecho/V2.0.x/en-Table.ts
index 4a98aaaaa..8d13f6655 100644
--- a/src/.vuepress/sidebar_timecho/V2.0.x/en-Table.ts
+++ b/src/.vuepress/sidebar_timecho/V2.0.x/en-Table.ts
@@ -97,6 +97,7 @@ export const enSidebar = {
       prefix: 'User-Manual/',
       children: [
         { text: 'Data Sync', link: 'Data-Sync_timecho' },
+        { text: 'UDF', link: 'User-defined-function' },
         {
           text: 'Security Permissions',
           collapsible: true,
diff --git a/src/.vuepress/sidebar_timecho/V2.0.x/zh-Table.ts b/src/.vuepress/sidebar_timecho/V2.0.x/zh-Table.ts
index 42308f4ec..8203e6e92 100644
--- a/src/.vuepress/sidebar_timecho/V2.0.x/zh-Table.ts
+++ b/src/.vuepress/sidebar_timecho/V2.0.x/zh-Table.ts
@@ -88,6 +88,7 @@ export const zhSidebar = {
       prefix: 'User-Manual/',
       children: [
         { text: '数据同步', link: 'Data-Sync_timecho' },
+        { text: '用户自定义函数', link: 'User-defined-function' },
         {
           text: '安全权限',
           collapsible: true,
diff --git a/src/UserGuide/Master/Table/User-Manual/User-defined-function.md b/src/UserGuide/Master/Table/User-Manual/User-defined-function.md
new file mode 100644
index 000000000..8190b0648
--- /dev/null
+++ b/src/UserGuide/Master/Table/User-Manual/User-defined-function.md
@@ -0,0 +1,350 @@
+<!--
+
+    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.
+
+-->
+
+# UDF
+
+## 1. UDF Introduction
+
+UDF refers to user-defined functions. IoTDB offers a variety of built-in time-series processing functions while supporting custom function extensions to fulfill advanced computational needs.
+
+IoTDB's table model supports two types of UDFs, as detailed below:
+
+| UDF Type                                | Function Type | Description                    |
+|-----------------------------------------|---------------|--------------------------------|
+| `UDSF（User-defined Scalar Function）`    | Scalar Function         | Processes ​1 row of k-column data, outputs ​1 row of 1-column data (one-to-one mapping). |
+| `UDAF（User-defined Aggregate Function）` | Aggregate Function       | Processes ​m rows of k-column data, outputs ​1 row of 1-column data (many-to-one reduction). |
+
+* `UDSF` can be used in any clause or expression where scalar functions are allowed, such as: SELECT clauses, WHERE conditions, etc.
+
+    * `select udsf1(s1) from table1 where udsf2(s1)>0`
+  
+* `UDAF` can be used in any clause or expression where aggregate functions are allowed, such as: SELECT clauses, HAVING conditions, etc.
+
+    * `select udaf1(s1), device_id from table1 group by device_id having udaf2(s1)>0 `
+
+
+## 2. UDF Management
+
+### 2.1 UDF Registration
+
+1. Prepare the UDF JAR Package
+
+   * The JAR should contain the UDF implementation class (e.g., `org.apache.iotdb.udf.ScalarFunctionExample`).
+   
+   * Deployment Options:
+   
+     * Local: Place the JAR in the `ext/udf` directory on **all cluster nodes**. 
+     
+     * Remote: Upload the JAR to a URI-accessible server (IoTDB will download and synchronize it across the cluster upon registration).
+     
+2. Register the UDF via SQL
+
+   ```sql
+   CREATE FUNCTION <UDF-NAME> AS <UDF-CLASS-FULL-PATHNAME> [USING URI <URI-STRING>]
+   ```
+   
+    Examples:
+
+    ```sql
+    -- Local deployment
+    CREATE FUNCTION contain_null AS 'org.apache.iotdb.udf.ScalarFunctionExample';
+    
+    -- Remote deployment (with URI)
+    CREATE FUNCTION contain_null AS 'org.apache.iotdb.udf.ScalarFunctionExample' USING URI 'http://jar/example.jar';
+    ```
+
+Key Notes:
+
+1. No Restart Required: UDFs can be loaded/unloaded dynamically without server restart.
+
+2. Naming Rules:
+
+* UDF names are ​case-insensitive.
+
+* Must not conflict with built-in function names.
+
+3. Model Isolation: UDFs in ​Table Model and ​Tree Model operate in separate namespaces.
+
+4. Class Collision Warning: Avoid implementing UDF classes with identical full names but different logic across JARs. If present, IoTDB may randomly load one, causing inconsistent behavior.
+
+
+### 2.2 UDF Uninstallation
+
+* SQL Syntax:
+
+```SQL
+DROP FUNCTION <UDF-NAME>
+```
+
+* Example: Uninstall the UDF from the previous example:
+
+```SQL
+DROP FUNCTION contain_null
+```
+
+### 2.3 UDF Inspection
+
+* View all registered UDFs and their statuses:
+
+```SQL
+SHOW FUNCTIONS
+```
+* Note: If the State shows UNAVAILABLE, errors may have occurred during registration/uninstallation. Check system logs and retry the operation until successful.
+
+
+### 2.4 UDF Configuration
+
+* Customize the UDF JAR storage directory in `iotdb-system.properties`:
+
+```Properties
+# UDF lib dir
+udf_lib_dir=ext/udf
+```
+
+## 3. UDF Development
+
+### 3.1 UDF Development Dependencies
+
+You can search for the dependencies in the examples below from [the Maven Repository](http://search.maven.org/). Please ensure to select dependency versions that match your target IoTDB server version.
+
+```XML
+<dependency>
+  <groupId>org.apache.iotdb</groupId>
+  <artifactId>udf-api</artifactId>
+  <version>2.0.0</version>
+  <scope>provided</scope>
+</dependency>
+```
+
+### 3.2 UDSF
+
+To develop a `UDSF (User-Defined Scalar Function)`, you need to implement the `org.apache.iotdb.udf.api.relational.ScalarFunction` interface.
+
+```java
+public interface ScalarFunction extends SQLFunction {
+  /**
+   * In this method, the user need to do the following things:
+   *
+   * <ul>
+   *   <li>Validate {@linkplain FunctionArguments}. Throw {@link UDFArgumentNotValidException} if
+   *       any parameter is not valid.
+   *   <li>Use {@linkplain FunctionArguments} to get input data types and infer output data type.
+   *   <li>Construct and return a {@linkplain ScalarFunctionAnalysis} object.
+   * </ul>
+   *
+   * @param arguments arguments used to validate
+   * @throws UDFArgumentNotValidException if any parameter is not valid
+   * @return the analysis result of the scalar function
+   */
+  ScalarFunctionAnalysis analyze(FunctionArguments arguments) throws UDFArgumentNotValidException;
+
+  /**
+   * This method is called after the ScalarFunction is instantiated and before the beginning of the
+   * transformation process. This method is mainly used to initialize the resources used in
+   * ScalarFunction.
+   *
+   * @param arguments used to parse the input arguments entered by the user
+   * @throws UDFException the user can throw errors if necessary
+   */
+  default void beforeStart(FunctionArguments arguments) throws UDFException {
+    // do nothing
+  }
+
+  /**
+   * This method will be called to process the transformation. In a single UDF query, this method
+   * may be called multiple times.
+   *
+   * @param input original input data row
+   * @throws UDFException the user can throw errors if necessary
+   */
+  Object evaluate(Record input) throws UDFException;
+
+  /** This method is mainly used to release the resources used in the ScalarFunction. */
+  default void beforeDestroy() {
+    // do nothing
+  }
+}
+```
+
+Interface Specification:
+
+| Interface Definition                                                     | Description                                                                                                                                                                                                                           | Required |
+| --------------------------------------------------------------- |---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------|
+| `ScalarFunctionAnalysis analyze(FunctionArguments arguments);`| 1. Validates the input column count, data types, and system parameters in `FunctionArguments`. Throws exceptions if invalid. <br> 2. Constructs `ScalarFunctionAnalysis` based on `FunctionArguments`, including output type information. | Yes      |
+| `void beforeStart(FunctionArguments arguments);`                | Custom initialization behavior before UDSF processes input data.                                                                                                                                                                         | No       |
+| `Object evaluate(Record input) throws UDFException;`            | Core UDSF logic that processes one row of input data and returns one row of output data.                                                                                                                                              | Yes      |
+| `void beforeDestroy();`                                         | Cleanup method for resource release. Called exactly once per instance by the framework after processing the last record.                                                                                                          | Np       |
+
+Current Fields in `ScalarFunctionAnalysis`:
+
+| Field Type| Field Name    | Default Value |
+| ---------- | ---------------- |---------------|
+| Type     | outputDataType | None          |
+
+[UDSF Implementation Example](https://github.com/apache/iotdb/blob/master/example/udf/src/main/java/org/apache/iotdb/udf/ScalarFunctionExample.java): Takes any number of columns of any data type as input and returns a boolean indicating whether the row contains NULL values.
+
+### 3.3 UDAF
+
+A complete `UDAF (User-Defined Aggregate Function)` definition requires implementation of two classes: `State` and `AggregateFunction`.
+
+#### 3.3.1 State Class
+
+To implement a `State` class, you need to implement the `org.apache.iotdb.udf.api.State` interface.
+
+```java
+public interface State {
+  /** Reset your state object to its initial state. */
+  void reset();
+
+  /**
+   * Serialize your state into byte array. The order of serialization must be consistent with
+   * deserialization.
+   */
+  byte[] serialize();
+
+  /**
+   * Deserialize byte array into your state. The order of deserialization must be consistent with
+   * serialization.
+   */
+  void deserialize(byte[] bytes);
+
+  /** Destroy state. You may release previously binding resource in this method. */
+  default void destroyState() {}
+  ;
+}
+```
+
+Interface Specification:
+
+| Interface Definition          | Description                                                                                                                          | Required |
+| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------- |----------|
+| `void reset() `                  | Resets the `State` object to its initial state. You should initialize all fields of the `State` class in this method, similar to a constructor.                  | Yes      |
+| `byte[] serialize()`             | Serializes the `State` into binary data. Used for internal `State` object transfer in IoTDB. Note: The serialization order must match the deserialization method below.   | Yes      |
+| `void deserialize(byte[] bytes)` | Deserializes binary data back into a `State` object. Used for internal `State` object transfer in IoTDB. Note: The deserialization order must match the serialization method above. | Yes      |
+| `void destroyState()`           | Performs resource cleanup operations. Called exactly once per instance by the framework at the end of its lifecycle.                                      | No       |
+
+#### 3.3.2 AggregateFunction Class
+ 
+To implement a `UDAF`, you need to implement the `org.apache.iotdb.udf.api.relational.AggregateFunction` interface.
+
+```java
+public interface AggregateFunction extends SQLFunction {
+
+  /**
+   * In this method, the user need to do the following things:
+   *
+   * <ul>
+   *   <li>Validate {@linkplain FunctionArguments}. Throw {@link UDFArgumentNotValidException} if
+   *       any parameter is not valid.
+   *   <li>Use {@linkplain FunctionArguments} to get input data types and infer output data type.
+   *   <li>Construct and return a {@linkplain AggregateFunctionAnalysis} object.
+   * </ul>
+   *
+   * @param arguments arguments used to validate
+   * @throws UDFArgumentNotValidException if any parameter is not valid
+   * @return the analysis result of the scalar function
+   */
+  AggregateFunctionAnalysis analyze(FunctionArguments arguments)
+      throws UDFArgumentNotValidException;
+
+  /**
+   * This method is called after the AggregateFunction is instantiated and before the beginning of
+   * the transformation process. This method is mainly used to initialize the resources used in
+   * AggregateFunction.
+   *
+   * @param arguments used to parse the input arguments entered by the user
+   * @throws UDFException the user can throw errors if necessary
+   */
+  default void beforeStart(FunctionArguments arguments) throws UDFException {
+    // do nothing
+  }
+
+  /** Create and initialize state. You may bind some resource in this method. */
+  State createState();
+
+  /**
+   * Update state with data columns.
+   *
+   * @param state state to be updated
+   * @param input original input data row
+   */
+  void addInput(State state, Record input);
+
+  /**
+   * Merge two state in execution engine.
+   *
+   * @param state current state
+   * @param rhs right-hand-side state to be merged
+   */
+  void combineState(State state, State rhs);
+
+  /**
+   * Calculate output value from final state
+   *
+   * @param state final state
+   * @param resultValue used to collect output data points
+   */
+  void outputFinal(State state, ResultValue resultValue);
+
+  /**
+   * Remove input data from state. This method is used to remove the data points that have been
+   * added to the state. Once it is implemented, {@linkplain
+   * AggregateFunctionAnalysis.Builder#removable(boolean)} should be set to true.
+   *
+   * @param state state to be updated
+   * @param input row to be removed
+   */
+  default void remove(State state, Record input) {
+    throw new UnsupportedOperationException();
+  }
+
+  /** This method is mainly used to release the resources used in the SQLFunction. */
+  default void beforeDestroy() {
+    // do nothing
+  }
+}
+```
+
+Interface Specification:
+
+| Interface Definition                                              | Description                                                                                                                                                                                     | Required |
+|-------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------|
+| `AggregateFunctionAnalysis analyze(FunctionArguments arguments);` | 1. Validates input column count, data types, and system parameters in `FunctionArguments` (throws exceptions if invalid).<br>2. Constructs `AggregateFunctionAnalysis` including output type and removable flag. | Yes      |
+| `void beforeStart(FunctionArguments arguments); `                 | Custom initialization before processing input data.                                                                                                                                                                   | No        |
+| `State createState();`                                            | Creates a `State` object (typically via default constructor with optional initial value overrides).                                                                                                                                                       | Yes      |
+| `void addInput(State state, Record input);`                       | Updates aggregation `state` by incorporating one input row.                                                                                                                                                      | Yes      |
+| `void combineState(State state, State rhs); `                     | Merges `rhs` state into `state` (critical for distributed execution where partial states are combined).                                                                                 | Yes      |
+| `void outputFinal(State state, ResultValue resultValue);`         | Computes final aggregation result (must produce exactly one output value per group).                                                                                                                                                  | Yes      |
+| `void remove(State state, Record input);`                         | Updates `state` by removing one input row (requires `removable=true` in `AggregateFunctionAnalysis`).                                                                                        | No        |
+| `void beforeDestroy();`                                           | Resource cleanup method (called exactly once per instance after final record processing).                                                                            | No       |
+
+Current Fields in `AggregateFunctionAnalysis`:
+
+| Field Type| Field Name    | Default Value  |
+| ---------- | ---------------- |-------|
+| Type     | outputDataType | None  |
+| boolean  | removable      | false |
+ 
+[UDAF Example](https://github.com/apache/iotdb/blob/master/example/udf/src/main/java/org/apache/iotdb/udf/AggregateFunctionExample.java): Counts non-NULL rows.
+
+### 3.4 Complete Maven Project Example
+
+For Maven-based implementations, refer to the sample project: [udf-example](https://github.com/apache/iotdb/tree/master/example/udf).
diff --git a/src/UserGuide/latest-Table/User-Manual/User-defined-function.md b/src/UserGuide/latest-Table/User-Manual/User-defined-function.md
new file mode 100644
index 000000000..8190b0648
--- /dev/null
+++ b/src/UserGuide/latest-Table/User-Manual/User-defined-function.md
@@ -0,0 +1,350 @@
+<!--
+
+    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.
+
+-->
+
+# UDF
+
+## 1. UDF Introduction
+
+UDF refers to user-defined functions. IoTDB offers a variety of built-in time-series processing functions while supporting custom function extensions to fulfill advanced computational needs.
+
+IoTDB's table model supports two types of UDFs, as detailed below:
+
+| UDF Type                                | Function Type | Description                    |
+|-----------------------------------------|---------------|--------------------------------|
+| `UDSF（User-defined Scalar Function）`    | Scalar Function         | Processes ​1 row of k-column data, outputs ​1 row of 1-column data (one-to-one mapping). |
+| `UDAF（User-defined Aggregate Function）` | Aggregate Function       | Processes ​m rows of k-column data, outputs ​1 row of 1-column data (many-to-one reduction). |
+
+* `UDSF` can be used in any clause or expression where scalar functions are allowed, such as: SELECT clauses, WHERE conditions, etc.
+
+    * `select udsf1(s1) from table1 where udsf2(s1)>0`
+  
+* `UDAF` can be used in any clause or expression where aggregate functions are allowed, such as: SELECT clauses, HAVING conditions, etc.
+
+    * `select udaf1(s1), device_id from table1 group by device_id having udaf2(s1)>0 `
+
+
+## 2. UDF Management
+
+### 2.1 UDF Registration
+
+1. Prepare the UDF JAR Package
+
+   * The JAR should contain the UDF implementation class (e.g., `org.apache.iotdb.udf.ScalarFunctionExample`).
+   
+   * Deployment Options:
+   
+     * Local: Place the JAR in the `ext/udf` directory on **all cluster nodes**. 
+     
+     * Remote: Upload the JAR to a URI-accessible server (IoTDB will download and synchronize it across the cluster upon registration).
+     
+2. Register the UDF via SQL
+
+   ```sql
+   CREATE FUNCTION <UDF-NAME> AS <UDF-CLASS-FULL-PATHNAME> [USING URI <URI-STRING>]
+   ```
+   
+    Examples:
+
+    ```sql
+    -- Local deployment
+    CREATE FUNCTION contain_null AS 'org.apache.iotdb.udf.ScalarFunctionExample';
+    
+    -- Remote deployment (with URI)
+    CREATE FUNCTION contain_null AS 'org.apache.iotdb.udf.ScalarFunctionExample' USING URI 'http://jar/example.jar';
+    ```
+
+Key Notes:
+
+1. No Restart Required: UDFs can be loaded/unloaded dynamically without server restart.
+
+2. Naming Rules:
+
+* UDF names are ​case-insensitive.
+
+* Must not conflict with built-in function names.
+
+3. Model Isolation: UDFs in ​Table Model and ​Tree Model operate in separate namespaces.
+
+4. Class Collision Warning: Avoid implementing UDF classes with identical full names but different logic across JARs. If present, IoTDB may randomly load one, causing inconsistent behavior.
+
+
+### 2.2 UDF Uninstallation
+
+* SQL Syntax:
+
+```SQL
+DROP FUNCTION <UDF-NAME>
+```
+
+* Example: Uninstall the UDF from the previous example:
+
+```SQL
+DROP FUNCTION contain_null
+```
+
+### 2.3 UDF Inspection
+
+* View all registered UDFs and their statuses:
+
+```SQL
+SHOW FUNCTIONS
+```
+* Note: If the State shows UNAVAILABLE, errors may have occurred during registration/uninstallation. Check system logs and retry the operation until successful.
+
+
+### 2.4 UDF Configuration
+
+* Customize the UDF JAR storage directory in `iotdb-system.properties`:
+
+```Properties
+# UDF lib dir
+udf_lib_dir=ext/udf
+```
+
+## 3. UDF Development
+
+### 3.1 UDF Development Dependencies
+
+You can search for the dependencies in the examples below from [the Maven Repository](http://search.maven.org/). Please ensure to select dependency versions that match your target IoTDB server version.
+
+```XML
+<dependency>
+  <groupId>org.apache.iotdb</groupId>
+  <artifactId>udf-api</artifactId>
+  <version>2.0.0</version>
+  <scope>provided</scope>
+</dependency>
+```
+
+### 3.2 UDSF
+
+To develop a `UDSF (User-Defined Scalar Function)`, you need to implement the `org.apache.iotdb.udf.api.relational.ScalarFunction` interface.
+
+```java
+public interface ScalarFunction extends SQLFunction {
+  /**
+   * In this method, the user need to do the following things:
+   *
+   * <ul>
+   *   <li>Validate {@linkplain FunctionArguments}. Throw {@link UDFArgumentNotValidException} if
+   *       any parameter is not valid.
+   *   <li>Use {@linkplain FunctionArguments} to get input data types and infer output data type.
+   *   <li>Construct and return a {@linkplain ScalarFunctionAnalysis} object.
+   * </ul>
+   *
+   * @param arguments arguments used to validate
+   * @throws UDFArgumentNotValidException if any parameter is not valid
+   * @return the analysis result of the scalar function
+   */
+  ScalarFunctionAnalysis analyze(FunctionArguments arguments) throws UDFArgumentNotValidException;
+
+  /**
+   * This method is called after the ScalarFunction is instantiated and before the beginning of the
+   * transformation process. This method is mainly used to initialize the resources used in
+   * ScalarFunction.
+   *
+   * @param arguments used to parse the input arguments entered by the user
+   * @throws UDFException the user can throw errors if necessary
+   */
+  default void beforeStart(FunctionArguments arguments) throws UDFException {
+    // do nothing
+  }
+
+  /**
+   * This method will be called to process the transformation. In a single UDF query, this method
+   * may be called multiple times.
+   *
+   * @param input original input data row
+   * @throws UDFException the user can throw errors if necessary
+   */
+  Object evaluate(Record input) throws UDFException;
+
+  /** This method is mainly used to release the resources used in the ScalarFunction. */
+  default void beforeDestroy() {
+    // do nothing
+  }
+}
+```
+
+Interface Specification:
+
+| Interface Definition                                                     | Description                                                                                                                                                                                                                           | Required |
+| --------------------------------------------------------------- |---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------|
+| `ScalarFunctionAnalysis analyze(FunctionArguments arguments);`| 1. Validates the input column count, data types, and system parameters in `FunctionArguments`. Throws exceptions if invalid. <br> 2. Constructs `ScalarFunctionAnalysis` based on `FunctionArguments`, including output type information. | Yes      |
+| `void beforeStart(FunctionArguments arguments);`                | Custom initialization behavior before UDSF processes input data.                                                                                                                                                                         | No       |
+| `Object evaluate(Record input) throws UDFException;`            | Core UDSF logic that processes one row of input data and returns one row of output data.                                                                                                                                              | Yes      |
+| `void beforeDestroy();`                                         | Cleanup method for resource release. Called exactly once per instance by the framework after processing the last record.                                                                                                          | Np       |
+
+Current Fields in `ScalarFunctionAnalysis`:
+
+| Field Type| Field Name    | Default Value |
+| ---------- | ---------------- |---------------|
+| Type     | outputDataType | None          |
+
+[UDSF Implementation Example](https://github.com/apache/iotdb/blob/master/example/udf/src/main/java/org/apache/iotdb/udf/ScalarFunctionExample.java): Takes any number of columns of any data type as input and returns a boolean indicating whether the row contains NULL values.
+
+### 3.3 UDAF
+
+A complete `UDAF (User-Defined Aggregate Function)` definition requires implementation of two classes: `State` and `AggregateFunction`.
+
+#### 3.3.1 State Class
+
+To implement a `State` class, you need to implement the `org.apache.iotdb.udf.api.State` interface.
+
+```java
+public interface State {
+  /** Reset your state object to its initial state. */
+  void reset();
+
+  /**
+   * Serialize your state into byte array. The order of serialization must be consistent with
+   * deserialization.
+   */
+  byte[] serialize();
+
+  /**
+   * Deserialize byte array into your state. The order of deserialization must be consistent with
+   * serialization.
+   */
+  void deserialize(byte[] bytes);
+
+  /** Destroy state. You may release previously binding resource in this method. */
+  default void destroyState() {}
+  ;
+}
+```
+
+Interface Specification:
+
+| Interface Definition          | Description                                                                                                                          | Required |
+| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------- |----------|
+| `void reset() `                  | Resets the `State` object to its initial state. You should initialize all fields of the `State` class in this method, similar to a constructor.                  | Yes      |
+| `byte[] serialize()`             | Serializes the `State` into binary data. Used for internal `State` object transfer in IoTDB. Note: The serialization order must match the deserialization method below.   | Yes      |
+| `void deserialize(byte[] bytes)` | Deserializes binary data back into a `State` object. Used for internal `State` object transfer in IoTDB. Note: The deserialization order must match the serialization method above. | Yes      |
+| `void destroyState()`           | Performs resource cleanup operations. Called exactly once per instance by the framework at the end of its lifecycle.                                      | No       |
+
+#### 3.3.2 AggregateFunction Class
+ 
+To implement a `UDAF`, you need to implement the `org.apache.iotdb.udf.api.relational.AggregateFunction` interface.
+
+```java
+public interface AggregateFunction extends SQLFunction {
+
+  /**
+   * In this method, the user need to do the following things:
+   *
+   * <ul>
+   *   <li>Validate {@linkplain FunctionArguments}. Throw {@link UDFArgumentNotValidException} if
+   *       any parameter is not valid.
+   *   <li>Use {@linkplain FunctionArguments} to get input data types and infer output data type.
+   *   <li>Construct and return a {@linkplain AggregateFunctionAnalysis} object.
+   * </ul>
+   *
+   * @param arguments arguments used to validate
+   * @throws UDFArgumentNotValidException if any parameter is not valid
+   * @return the analysis result of the scalar function
+   */
+  AggregateFunctionAnalysis analyze(FunctionArguments arguments)
+      throws UDFArgumentNotValidException;
+
+  /**
+   * This method is called after the AggregateFunction is instantiated and before the beginning of
+   * the transformation process. This method is mainly used to initialize the resources used in
+   * AggregateFunction.
+   *
+   * @param arguments used to parse the input arguments entered by the user
+   * @throws UDFException the user can throw errors if necessary
+   */
+  default void beforeStart(FunctionArguments arguments) throws UDFException {
+    // do nothing
+  }
+
+  /** Create and initialize state. You may bind some resource in this method. */
+  State createState();
+
+  /**
+   * Update state with data columns.
+   *
+   * @param state state to be updated
+   * @param input original input data row
+   */
+  void addInput(State state, Record input);
+
+  /**
+   * Merge two state in execution engine.
+   *
+   * @param state current state
+   * @param rhs right-hand-side state to be merged
+   */
+  void combineState(State state, State rhs);
+
+  /**
+   * Calculate output value from final state
+   *
+   * @param state final state
+   * @param resultValue used to collect output data points
+   */
+  void outputFinal(State state, ResultValue resultValue);
+
+  /**
+   * Remove input data from state. This method is used to remove the data points that have been
+   * added to the state. Once it is implemented, {@linkplain
+   * AggregateFunctionAnalysis.Builder#removable(boolean)} should be set to true.
+   *
+   * @param state state to be updated
+   * @param input row to be removed
+   */
+  default void remove(State state, Record input) {
+    throw new UnsupportedOperationException();
+  }
+
+  /** This method is mainly used to release the resources used in the SQLFunction. */
+  default void beforeDestroy() {
+    // do nothing
+  }
+}
+```
+
+Interface Specification:
+
+| Interface Definition                                              | Description                                                                                                                                                                                     | Required |
+|-------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------|
+| `AggregateFunctionAnalysis analyze(FunctionArguments arguments);` | 1. Validates input column count, data types, and system parameters in `FunctionArguments` (throws exceptions if invalid).<br>2. Constructs `AggregateFunctionAnalysis` including output type and removable flag. | Yes      |
+| `void beforeStart(FunctionArguments arguments); `                 | Custom initialization before processing input data.                                                                                                                                                                   | No        |
+| `State createState();`                                            | Creates a `State` object (typically via default constructor with optional initial value overrides).                                                                                                                                                       | Yes      |
+| `void addInput(State state, Record input);`                       | Updates aggregation `state` by incorporating one input row.                                                                                                                                                      | Yes      |
+| `void combineState(State state, State rhs); `                     | Merges `rhs` state into `state` (critical for distributed execution where partial states are combined).                                                                                 | Yes      |
+| `void outputFinal(State state, ResultValue resultValue);`         | Computes final aggregation result (must produce exactly one output value per group).                                                                                                                                                  | Yes      |
+| `void remove(State state, Record input);`                         | Updates `state` by removing one input row (requires `removable=true` in `AggregateFunctionAnalysis`).                                                                                        | No        |
+| `void beforeDestroy();`                                           | Resource cleanup method (called exactly once per instance after final record processing).                                                                            | No       |
+
+Current Fields in `AggregateFunctionAnalysis`:
+
+| Field Type| Field Name    | Default Value  |
+| ---------- | ---------------- |-------|
+| Type     | outputDataType | None  |
+| boolean  | removable      | false |
+ 
+[UDAF Example](https://github.com/apache/iotdb/blob/master/example/udf/src/main/java/org/apache/iotdb/udf/AggregateFunctionExample.java): Counts non-NULL rows.
+
+### 3.4 Complete Maven Project Example
+
+For Maven-based implementations, refer to the sample project: [udf-example](https://github.com/apache/iotdb/tree/master/example/udf).
diff --git a/src/zh/UserGuide/Master/Table/User-Manual/User-defined-function.md b/src/zh/UserGuide/Master/Table/User-Manual/User-defined-function.md
new file mode 100644
index 000000000..22275669a
--- /dev/null
+++ b/src/zh/UserGuide/Master/Table/User-Manual/User-defined-function.md
@@ -0,0 +1,334 @@
+<!--
+
+    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.
+
+-->
+
+# 用户自定义函数
+
+## 1. UDF介绍
+
+UDF（User Defined Function）即用户自定义函数，IoTDB 提供多种内置的时序处理函数，也支持扩展自定义函数来满足更多的计算需求。
+
+IoTDB 表模型中支持两种类型的 UDF ，如下表所示。
+
+| UDF 类型                                | 函数类型 | 描述                                              |
+| ----------------------------------------- | ---------- | --------------------------------------------------- |
+| `UDSF（User-defined Scalar Function）`    | 标量函数 | 输入 k 列 1 行数据，输出1 列 1 行数据（一对一）。 |
+| `UDAF（User-defined Aggregate Function）` | 聚合函数 | 输入k 列 m 行数据，输出1 列 1 行数据（多对一）。  |
+
+* `UDSF` 可用于标量函数出现的任何子句和表达式中，如select子句、where子句等。
+    * `select udsf1(s1) from table1 where udsf2(s1)>0`
+* `UDAF` 可用于聚合函数出现的任何子句和表达式中，如select子句、having子句等；
+    * `select udaf1(s1), device_id from table1 group by device_id having udaf2(s1)>0 `
+
+## 2. UDF 管理
+
+### 2.1 UDF 注册
+
+
+1. 准备 UDF 实现的 JAR 包，其中包含 UDF 实现类，如`org.apache.iotdb.udf.ScalarFunctionExample`。
+
+    Jar 包的放置有两种方式：
+
+* 本地：需要将 JAR 包放置到集群**所有节点**的 `ext/udf`目录下。
+* 远端：需要将 JAR 包上传到 URI 服务器上并确保 IoTDB 实例能够访问该 URI 服务器（注册成功后IoTDB 会下载 JAR 包并同步到整个集群）。
+
+2. 使用以下 SQL 语句注册 UDF
+
+```SQL
+CREATE FUNCTION <UDF-NAME> AS <UDF-CLASS-FULL-PATHNAME> (USING URI URI-STRING)
+```
+
+* 示例
+
+```SQL
+-- 本地
+CREATE FUNCTION contain_null AS 'org.apache.iotdb.udf.ScalarFunctionExample';
+
+-- 远端
+CREATE FUNCTION contain_null AS 'org.apache.iotdb.udf.ScalarFunctionExample' USING URI 'http://jar/example.jar'
+```
+
+**注意：**
+
+1. UDF 在装载过程中无需启停服务器。
+2. UDF 名称大小写不敏感，不能与 IoTDB 内置函数重名。
+3. 表模型和树模型的 UDF 空间相互独立。
+4. 避免在不同的 JAR 包中创建全类名相同但功能逻辑不同的 UDF 类。如果存在，系统在执行 UDF 时会随机加载其中一个，造成执行行为不一致。
+
+### 2.2 UDF 卸载
+
+SQL 语法如下：
+
+```SQL
+DROP FUNCTION <UDF-NAME>
+```
+
+示例：卸载上述例子的 UDF：
+
+```SQL
+DROP FUNCTION contain_null
+```
+
+### 2.3 UDF 查看
+
+* 如果 State 为 UNAVAILABLE，可能是在注册或卸载过程中系统发生了错误，请查看系统日志进行排查，重新注册或卸载 UDF 直至成功即可。
+
+```SQL
+SHOW FUNCTIONS
+```
+
+### 2.4 UDF 配置
+
+* 可以在 `iotdb-system.properties` 中配置 UDF Jar 文件的存储目录：
+
+```Properties
+# UDF lib dir
+udf_lib_dir=ext/udf
+```
+
+## 3. UDF 开发
+
+### 3.1 UDF 依赖
+
+可以从 [Maven 库](http://search.maven.org/) 中搜索下面示例中的依赖，请注意选择和目标 IoTDB 服务器版本相同的依赖版本。
+
+```XML
+<dependency>
+  <groupId>org.apache.iotdb</groupId>
+  <artifactId>udf-api</artifactId>
+  <version>2.0.0</version>
+  <scope>provided</scope>
+</dependency>
+```
+
+### 3.2 标量函数（UDSF）
+
+编写一个 UDSF 需要实现`org.apache.iotdb.udf.api.relational.ScalarFunction`接口。
+
+```java
+public interface ScalarFunction extends SQLFunction {
+  /**
+   * In this method, the user need to do the following things:
+   *
+   * <ul>
+   *   <li>Validate {@linkplain FunctionArguments}. Throw {@link UDFArgumentNotValidException} if
+   *       any parameter is not valid.
+   *   <li>Use {@linkplain FunctionArguments} to get input data types and infer output data type.
+   *   <li>Construct and return a {@linkplain ScalarFunctionAnalysis} object.
+   * </ul>
+   *
+   * @param arguments arguments used to validate
+   * @throws UDFArgumentNotValidException if any parameter is not valid
+   * @return the analysis result of the scalar function
+   */
+  ScalarFunctionAnalysis analyze(FunctionArguments arguments) throws UDFArgumentNotValidException;
+
+  /**
+   * This method is called after the ScalarFunction is instantiated and before the beginning of the
+   * transformation process. This method is mainly used to initialize the resources used in
+   * ScalarFunction.
+   *
+   * @param arguments used to parse the input arguments entered by the user
+   * @throws UDFException the user can throw errors if necessary
+   */
+  default void beforeStart(FunctionArguments arguments) throws UDFException {
+    // do nothing
+  }
+
+  /**
+   * This method will be called to process the transformation. In a single UDF query, this method
+   * may be called multiple times.
+   *
+   * @param input original input data row
+   * @throws UDFException the user can throw errors if necessary
+   */
+  Object evaluate(Record input) throws UDFException;
+
+  /** This method is mainly used to release the resources used in the ScalarFunction. */
+  default void beforeDestroy() {
+    // do nothing
+  }
+}
+```
+
+接口说明：
+
+| 接口定义                                                      | 描述                                                                                                                        | 是否必须 |
+| --------------------------------------------------------------- |---------------------------------------------------------------------------------------------------------------------------| ---------- |
+| `ScalarFunctionAnalysis analyze(FunctionArguments arguments);`| 1. 校验`FunctionArguments`中的输入列数、数据类型、系统参数等是否合法，不合法则抛出异常。<br> 2. 根据`FunctionArguments`构造`ScalarFunctionAnalysis`，包括输出类型等信息。 | 是       |
+| `void beforeStart(FunctionArguments arguments);`                | 在 UDSF 处理输入数据前，调用用户自定义的初始化行为                                                                                              | 否       |
+| `Object evaluate(Record input) throws UDFException;`            | UDSF 处理逻辑，根据一行输入数据，返回一行输出数据。                                                                                              | 是       |
+| `void beforeDestroy();`                                         | UDSF 的结束方法，您可以在此方法中进行一些资源释放等的操作。此方法由框架调用。对于一个实例而言，生命周期中会且只会被调用一次，即在处理完最后一条记录之后被调用。                                        | 否       |
+
+目前 ScalarFunctionAnalysis 中的字段：
+
+| 字段类型 | 字段名称       | 默认值 |
+| ---------- | ---------------- | -------- |
+| Type     | outputDataType | 无     |
+
+示例：[UDSF 的实现示例](https://github.com/apache/iotdb/blob/master/example/udf/src/main/java/org/apache/iotdb/udf/ScalarFunctionExample.java)，输入任意数据类型的任意多列，返回一个布尔值，代表该行输入是否包含 NULL 值。
+
+### 3.3 聚合函数（UDAF）
+
+一个完整的 UDAF 定义涉及到 `State` 和 `AggregateFunction` 两个类。
+
+#### 3.3.1 State 类
+
+编写一个 State 类需要实现`org.apache.iotdb.udf.api.State`接口。
+
+```c++
+public interface State {
+  /** Reset your state object to its initial state. */
+  void reset();
+
+  /**
+   * Serialize your state into byte array. The order of serialization must be consistent with
+   * deserialization.
+   */
+  byte[] serialize();
+
+  /**
+   * Deserialize byte array into your state. The order of deserialization must be consistent with
+   * serialization.
+   */
+  void deserialize(byte[] bytes);
+
+  /** Destroy state. You may release previously binding resource in this method. */
+  default void destroyState() {}
+  ;
+}
+```
+
+接口说明：
+
+| 接口定义                       | 描述                                                                                                                          | 是否必须 |
+| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------- | ---------- |
+| `void reset() `                  | 将`State`对象重置为初始的状态，您需要像编写构造函数一样，在该方法内填入`State`类中各个字段的初始值。                  | 是       |
+| `byte[] serialize()`             | 将`State`序列化为二进制数据。该方法用于 IoTDB 内部的`State`对象传递，注意序列化的顺序必须和下面的反序列化方法一致。   | 是       |
+| `void deserialize(byte[] bytes)` | 将二进制数据反序列化为`State`。该方法用于 IoTDB 内部的`State`对象传递，注意反序列化的顺序必须和上面的序列化方法一致。 | 是       |
+| `void destroyState()`           | 进行资源释放等的操作。此方法由框架调用。对于一个实例而言，生命周期中会且只会被调用一次。                                      | 否      |
+
+#### 3.3.2 AggregateFunction 类
+
+编写一个 UDAF 需要实现 `org.apache.iotdb.udf.api.relational.AggregateFunction`接口。
+
+```java
+public interface AggregateFunction extends SQLFunction {
+
+  /**
+   * In this method, the user need to do the following things:
+   *
+   * <ul>
+   *   <li>Validate {@linkplain FunctionArguments}. Throw {@link UDFArgumentNotValidException} if
+   *       any parameter is not valid.
+   *   <li>Use {@linkplain FunctionArguments} to get input data types and infer output data type.
+   *   <li>Construct and return a {@linkplain AggregateFunctionAnalysis} object.
+   * </ul>
+   *
+   * @param arguments arguments used to validate
+   * @throws UDFArgumentNotValidException if any parameter is not valid
+   * @return the analysis result of the scalar function
+   */
+  AggregateFunctionAnalysis analyze(FunctionArguments arguments)
+      throws UDFArgumentNotValidException;
+
+  /**
+   * This method is called after the AggregateFunction is instantiated and before the beginning of
+   * the transformation process. This method is mainly used to initialize the resources used in
+   * AggregateFunction.
+   *
+   * @param arguments used to parse the input arguments entered by the user
+   * @throws UDFException the user can throw errors if necessary
+   */
+  default void beforeStart(FunctionArguments arguments) throws UDFException {
+    // do nothing
+  }
+
+  /** Create and initialize state. You may bind some resource in this method. */
+  State createState();
+
+  /**
+   * Update state with data columns.
+   *
+   * @param state state to be updated
+   * @param input original input data row
+   */
+  void addInput(State state, Record input);
+
+  /**
+   * Merge two state in execution engine.
+   *
+   * @param state current state
+   * @param rhs right-hand-side state to be merged
+   */
+  void combineState(State state, State rhs);
+
+  /**
+   * Calculate output value from final state
+   *
+   * @param state final state
+   * @param resultValue used to collect output data points
+   */
+  void outputFinal(State state, ResultValue resultValue);
+
+  /**
+   * Remove input data from state. This method is used to remove the data points that have been
+   * added to the state. Once it is implemented, {@linkplain
+   * AggregateFunctionAnalysis.Builder#removable(boolean)} should be set to true.
+   *
+   * @param state state to be updated
+   * @param input row to be removed
+   */
+  default void remove(State state, Record input) {
+    throw new UnsupportedOperationException();
+  }
+
+  /** This method is mainly used to release the resources used in the SQLFunction. */
+  default void beforeDestroy() {
+    // do nothing
+  }
+}
+```
+
+接口说明：
+
+| 接口定义                                                        | 描述                                                                                                                                      | 是否必须           |
+| ----------------------------------------------------------------- |-----------------------------------------------------------------------------------------------------------------------------------------|----------------|
+| `AggregateFunctionAnalysis analyze(FunctionArguments arguments);` | 1. 校验`FunctionArguments`中的输入列数、数据类型、系统参数等是否合法，不合法则抛出异常。<br> 2. 根据`FunctionArguments`构造`AggregateFunctionAnalysis`，包括输出类型、removable 等信息。 | 是              |
+| `void beforeStart(FunctionArguments arguments); `                 | 在 UDAF 处理输入数据前，调用用户自定义的初始化行为                                                                                                            | 否              |
+| `State createState();`                                            | 创建`State`对象，一般只需要调用默认构造函数，然后按需修改默认的初始值即可。                                                                                               | 是              |
+| `void addInput(State state, Record input);`                       | 更新`State`对象，将输入的一行*​ ​*`Record`数据添加到聚合状态中。                                                                                              | 是              |
+| `void combineState(State state, State rhs); `                     | 将`rhs`状态合并至`state`状态中。在分布式场景下，同一组的数据可能分布在不同节点上，IoTDB 会为每个节点上的部分数据生成一个`State`对象，然后调用该方法合并成完整的`State`。                                    | 是              |
+| `void outputFinal(State state, ResultValue resultValue);`         | 根据`State`中的数据，计算出最终的聚合结果。注意根据聚合的语义，每一组只能输出一个值。                                                                                          | 是              |
+| `void remove(State state, Record input);`| 更新`State`对象，将输入的一行*​ ​*`Record`数据从聚合状态中剔除。**实现该方法需要设置 AggregateFunctionAnalysis 中的 removable 字段为 true。**                                | 否              |
+| `void beforeDestroy();`| UDSF 的结束方法，您可以在此方法中进行一些资源释放等的操作。此方法由框架调用。对于一个实例而言，生命周期中会且只会被调用一次，即在处理完最后一条记录之后被调用。                                                      | 否              |
+
+目前 AggregateFunctionAnalysis 中的字段：
+
+| 字段类型 | 字段名称       | 默认值 |
+| ---------- | ---------------- | -------- |
+| Type     | outputDataType | 无     |
+| boolean  | removable      | false  |
+
+示例：[UDAF 的实现示例](https://github.com/apache/iotdb/blob/master/example/udf/src/main/java/org/apache/iotdb/udf/AggregateFunctionExample.java)，计算不为 NULL 的行数。
+
+### 3.4 完整Maven项目示例
+
+如果使用 [Maven](http://search.maven.org/)，可以参考示例项目[udf-example](https://github.com/apache/iotdb/tree/master/example/udf)。
diff --git a/src/zh/UserGuide/latest-Table/User-Manual/User-defined-function.md b/src/zh/UserGuide/latest-Table/User-Manual/User-defined-function.md
new file mode 100644
index 000000000..22275669a
--- /dev/null
+++ b/src/zh/UserGuide/latest-Table/User-Manual/User-defined-function.md
@@ -0,0 +1,334 @@
+<!--
+
+    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.
+
+-->
+
+# 用户自定义函数
+
+## 1. UDF介绍
+
+UDF（User Defined Function）即用户自定义函数，IoTDB 提供多种内置的时序处理函数，也支持扩展自定义函数来满足更多的计算需求。
+
+IoTDB 表模型中支持两种类型的 UDF ，如下表所示。
+
+| UDF 类型                                | 函数类型 | 描述                                              |
+| ----------------------------------------- | ---------- | --------------------------------------------------- |
+| `UDSF（User-defined Scalar Function）`    | 标量函数 | 输入 k 列 1 行数据，输出1 列 1 行数据（一对一）。 |
+| `UDAF（User-defined Aggregate Function）` | 聚合函数 | 输入k 列 m 行数据，输出1 列 1 行数据（多对一）。  |
+
+* `UDSF` 可用于标量函数出现的任何子句和表达式中，如select子句、where子句等。
+    * `select udsf1(s1) from table1 where udsf2(s1)>0`
+* `UDAF` 可用于聚合函数出现的任何子句和表达式中，如select子句、having子句等；
+    * `select udaf1(s1), device_id from table1 group by device_id having udaf2(s1)>0 `
+
+## 2. UDF 管理
+
+### 2.1 UDF 注册
+
+
+1. 准备 UDF 实现的 JAR 包，其中包含 UDF 实现类，如`org.apache.iotdb.udf.ScalarFunctionExample`。
+
+    Jar 包的放置有两种方式：
+
+* 本地：需要将 JAR 包放置到集群**所有节点**的 `ext/udf`目录下。
+* 远端：需要将 JAR 包上传到 URI 服务器上并确保 IoTDB 实例能够访问该 URI 服务器（注册成功后IoTDB 会下载 JAR 包并同步到整个集群）。
+
+2. 使用以下 SQL 语句注册 UDF
+
+```SQL
+CREATE FUNCTION <UDF-NAME> AS <UDF-CLASS-FULL-PATHNAME> (USING URI URI-STRING)
+```
+
+* 示例
+
+```SQL
+-- 本地
+CREATE FUNCTION contain_null AS 'org.apache.iotdb.udf.ScalarFunctionExample';
+
+-- 远端
+CREATE FUNCTION contain_null AS 'org.apache.iotdb.udf.ScalarFunctionExample' USING URI 'http://jar/example.jar'
+```
+
+**注意：**
+
+1. UDF 在装载过程中无需启停服务器。
+2. UDF 名称大小写不敏感，不能与 IoTDB 内置函数重名。
+3. 表模型和树模型的 UDF 空间相互独立。
+4. 避免在不同的 JAR 包中创建全类名相同但功能逻辑不同的 UDF 类。如果存在，系统在执行 UDF 时会随机加载其中一个，造成执行行为不一致。
+
+### 2.2 UDF 卸载
+
+SQL 语法如下：
+
+```SQL
+DROP FUNCTION <UDF-NAME>
+```
+
+示例：卸载上述例子的 UDF：
+
+```SQL
+DROP FUNCTION contain_null
+```
+
+### 2.3 UDF 查看
+
+* 如果 State 为 UNAVAILABLE，可能是在注册或卸载过程中系统发生了错误，请查看系统日志进行排查，重新注册或卸载 UDF 直至成功即可。
+
+```SQL
+SHOW FUNCTIONS
+```
+
+### 2.4 UDF 配置
+
+* 可以在 `iotdb-system.properties` 中配置 UDF Jar 文件的存储目录：
+
+```Properties
+# UDF lib dir
+udf_lib_dir=ext/udf
+```
+
+## 3. UDF 开发
+
+### 3.1 UDF 依赖
+
+可以从 [Maven 库](http://search.maven.org/) 中搜索下面示例中的依赖，请注意选择和目标 IoTDB 服务器版本相同的依赖版本。
+
+```XML
+<dependency>
+  <groupId>org.apache.iotdb</groupId>
+  <artifactId>udf-api</artifactId>
+  <version>2.0.0</version>
+  <scope>provided</scope>
+</dependency>
+```
+
+### 3.2 标量函数（UDSF）
+
+编写一个 UDSF 需要实现`org.apache.iotdb.udf.api.relational.ScalarFunction`接口。
+
+```java
+public interface ScalarFunction extends SQLFunction {
+  /**
+   * In this method, the user need to do the following things:
+   *
+   * <ul>
+   *   <li>Validate {@linkplain FunctionArguments}. Throw {@link UDFArgumentNotValidException} if
+   *       any parameter is not valid.
+   *   <li>Use {@linkplain FunctionArguments} to get input data types and infer output data type.
+   *   <li>Construct and return a {@linkplain ScalarFunctionAnalysis} object.
+   * </ul>
+   *
+   * @param arguments arguments used to validate
+   * @throws UDFArgumentNotValidException if any parameter is not valid
+   * @return the analysis result of the scalar function
+   */
+  ScalarFunctionAnalysis analyze(FunctionArguments arguments) throws UDFArgumentNotValidException;
+
+  /**
+   * This method is called after the ScalarFunction is instantiated and before the beginning of the
+   * transformation process. This method is mainly used to initialize the resources used in
+   * ScalarFunction.
+   *
+   * @param arguments used to parse the input arguments entered by the user
+   * @throws UDFException the user can throw errors if necessary
+   */
+  default void beforeStart(FunctionArguments arguments) throws UDFException {
+    // do nothing
+  }
+
+  /**
+   * This method will be called to process the transformation. In a single UDF query, this method
+   * may be called multiple times.
+   *
+   * @param input original input data row
+   * @throws UDFException the user can throw errors if necessary
+   */
+  Object evaluate(Record input) throws UDFException;
+
+  /** This method is mainly used to release the resources used in the ScalarFunction. */
+  default void beforeDestroy() {
+    // do nothing
+  }
+}
+```
+
+接口说明：
+
+| 接口定义                                                      | 描述                                                                                                                        | 是否必须 |
+| --------------------------------------------------------------- |---------------------------------------------------------------------------------------------------------------------------| ---------- |
+| `ScalarFunctionAnalysis analyze(FunctionArguments arguments);`| 1. 校验`FunctionArguments`中的输入列数、数据类型、系统参数等是否合法，不合法则抛出异常。<br> 2. 根据`FunctionArguments`构造`ScalarFunctionAnalysis`，包括输出类型等信息。 | 是       |
+| `void beforeStart(FunctionArguments arguments);`                | 在 UDSF 处理输入数据前，调用用户自定义的初始化行为                                                                                              | 否       |
+| `Object evaluate(Record input) throws UDFException;`            | UDSF 处理逻辑，根据一行输入数据，返回一行输出数据。                                                                                              | 是       |
+| `void beforeDestroy();`                                         | UDSF 的结束方法，您可以在此方法中进行一些资源释放等的操作。此方法由框架调用。对于一个实例而言，生命周期中会且只会被调用一次，即在处理完最后一条记录之后被调用。                                        | 否       |
+
+目前 ScalarFunctionAnalysis 中的字段：
+
+| 字段类型 | 字段名称       | 默认值 |
+| ---------- | ---------------- | -------- |
+| Type     | outputDataType | 无     |
+
+示例：[UDSF 的实现示例](https://github.com/apache/iotdb/blob/master/example/udf/src/main/java/org/apache/iotdb/udf/ScalarFunctionExample.java)，输入任意数据类型的任意多列，返回一个布尔值，代表该行输入是否包含 NULL 值。
+
+### 3.3 聚合函数（UDAF）
+
+一个完整的 UDAF 定义涉及到 `State` 和 `AggregateFunction` 两个类。
+
+#### 3.3.1 State 类
+
+编写一个 State 类需要实现`org.apache.iotdb.udf.api.State`接口。
+
+```c++
+public interface State {
+  /** Reset your state object to its initial state. */
+  void reset();
+
+  /**
+   * Serialize your state into byte array. The order of serialization must be consistent with
+   * deserialization.
+   */
+  byte[] serialize();
+
+  /**
+   * Deserialize byte array into your state. The order of deserialization must be consistent with
+   * serialization.
+   */
+  void deserialize(byte[] bytes);
+
+  /** Destroy state. You may release previously binding resource in this method. */
+  default void destroyState() {}
+  ;
+}
+```
+
+接口说明：
+
+| 接口定义                       | 描述                                                                                                                          | 是否必须 |
+| -------------------------------- | ------------------------------------------------------------------------------------------------------------------------------- | ---------- |
+| `void reset() `                  | 将`State`对象重置为初始的状态，您需要像编写构造函数一样，在该方法内填入`State`类中各个字段的初始值。                  | 是       |
+| `byte[] serialize()`             | 将`State`序列化为二进制数据。该方法用于 IoTDB 内部的`State`对象传递，注意序列化的顺序必须和下面的反序列化方法一致。   | 是       |
+| `void deserialize(byte[] bytes)` | 将二进制数据反序列化为`State`。该方法用于 IoTDB 内部的`State`对象传递，注意反序列化的顺序必须和上面的序列化方法一致。 | 是       |
+| `void destroyState()`           | 进行资源释放等的操作。此方法由框架调用。对于一个实例而言，生命周期中会且只会被调用一次。                                      | 否      |
+
+#### 3.3.2 AggregateFunction 类
+
+编写一个 UDAF 需要实现 `org.apache.iotdb.udf.api.relational.AggregateFunction`接口。
+
+```java
+public interface AggregateFunction extends SQLFunction {
+
+  /**
+   * In this method, the user need to do the following things:
+   *
+   * <ul>
+   *   <li>Validate {@linkplain FunctionArguments}. Throw {@link UDFArgumentNotValidException} if
+   *       any parameter is not valid.
+   *   <li>Use {@linkplain FunctionArguments} to get input data types and infer output data type.
+   *   <li>Construct and return a {@linkplain AggregateFunctionAnalysis} object.
+   * </ul>
+   *
+   * @param arguments arguments used to validate
+   * @throws UDFArgumentNotValidException if any parameter is not valid
+   * @return the analysis result of the scalar function
+   */
+  AggregateFunctionAnalysis analyze(FunctionArguments arguments)
+      throws UDFArgumentNotValidException;
+
+  /**
+   * This method is called after the AggregateFunction is instantiated and before the beginning of
+   * the transformation process. This method is mainly used to initialize the resources used in
+   * AggregateFunction.
+   *
+   * @param arguments used to parse the input arguments entered by the user
+   * @throws UDFException the user can throw errors if necessary
+   */
+  default void beforeStart(FunctionArguments arguments) throws UDFException {
+    // do nothing
+  }
+
+  /** Create and initialize state. You may bind some resource in this method. */
+  State createState();
+
+  /**
+   * Update state with data columns.
+   *
+   * @param state state to be updated
+   * @param input original input data row
+   */
+  void addInput(State state, Record input);
+
+  /**
+   * Merge two state in execution engine.
+   *
+   * @param state current state
+   * @param rhs right-hand-side state to be merged
+   */
+  void combineState(State state, State rhs);
+
+  /**
+   * Calculate output value from final state
+   *
+   * @param state final state
+   * @param resultValue used to collect output data points
+   */
+  void outputFinal(State state, ResultValue resultValue);
+
+  /**
+   * Remove input data from state. This method is used to remove the data points that have been
+   * added to the state. Once it is implemented, {@linkplain
+   * AggregateFunctionAnalysis.Builder#removable(boolean)} should be set to true.
+   *
+   * @param state state to be updated
+   * @param input row to be removed
+   */
+  default void remove(State state, Record input) {
+    throw new UnsupportedOperationException();
+  }
+
+  /** This method is mainly used to release the resources used in the SQLFunction. */
+  default void beforeDestroy() {
+    // do nothing
+  }
+}
+```
+
+接口说明：
+
+| 接口定义                                                        | 描述                                                                                                                                      | 是否必须           |
+| ----------------------------------------------------------------- |-----------------------------------------------------------------------------------------------------------------------------------------|----------------|
+| `AggregateFunctionAnalysis analyze(FunctionArguments arguments);` | 1. 校验`FunctionArguments`中的输入列数、数据类型、系统参数等是否合法，不合法则抛出异常。<br> 2. 根据`FunctionArguments`构造`AggregateFunctionAnalysis`，包括输出类型、removable 等信息。 | 是              |
+| `void beforeStart(FunctionArguments arguments); `                 | 在 UDAF 处理输入数据前，调用用户自定义的初始化行为                                                                                                            | 否              |
+| `State createState();`                                            | 创建`State`对象，一般只需要调用默认构造函数，然后按需修改默认的初始值即可。                                                                                               | 是              |
+| `void addInput(State state, Record input);`                       | 更新`State`对象，将输入的一行*​ ​*`Record`数据添加到聚合状态中。                                                                                              | 是              |
+| `void combineState(State state, State rhs); `                     | 将`rhs`状态合并至`state`状态中。在分布式场景下，同一组的数据可能分布在不同节点上，IoTDB 会为每个节点上的部分数据生成一个`State`对象，然后调用该方法合并成完整的`State`。                                    | 是              |
+| `void outputFinal(State state, ResultValue resultValue);`         | 根据`State`中的数据，计算出最终的聚合结果。注意根据聚合的语义，每一组只能输出一个值。                                                                                          | 是              |
+| `void remove(State state, Record input);`| 更新`State`对象，将输入的一行*​ ​*`Record`数据从聚合状态中剔除。**实现该方法需要设置 AggregateFunctionAnalysis 中的 removable 字段为 true。**                                | 否              |
+| `void beforeDestroy();`| UDSF 的结束方法，您可以在此方法中进行一些资源释放等的操作。此方法由框架调用。对于一个实例而言，生命周期中会且只会被调用一次，即在处理完最后一条记录之后被调用。                                                      | 否              |
+
+目前 AggregateFunctionAnalysis 中的字段：
+
+| 字段类型 | 字段名称       | 默认值 |
+| ---------- | ---------------- | -------- |
+| Type     | outputDataType | 无     |
+| boolean  | removable      | false  |
+
+示例：[UDAF 的实现示例](https://github.com/apache/iotdb/blob/master/example/udf/src/main/java/org/apache/iotdb/udf/AggregateFunctionExample.java)，计算不为 NULL 的行数。
+
+### 3.4 完整Maven项目示例
+
+如果使用 [Maven](http://search.maven.org/)，可以参考示例项目[udf-example](https://github.com/apache/iotdb/tree/master/example/udf)。