src/zh/UserGuide/latest/Tools-System/Schema-Export-Tool_timecho.md

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# 元数据导出

## 1. 功能概述

元数据导出工具 `export-schema.sh/bat` 位于tools 目录下，能够将 IoTDB 中指定数据库下的元数据导出为脚本文件。

## 2. 功能详解

### 2.1 参数介绍

| 参数缩写            | 参数全称                 | 参数含义                                                               | 是否为必填项                      | 默认值                                   |
| --------------------- | -------------------------- | ------------------------------------------------------------------------ | ----------------------------------- |---------------------------------------|
| `-h`            | `-- host`            | 主机名                                                                 | 否                                | 127.0.0.1                             |
| `-p`            | `--port`             | 端口号                                                                 | 否                                | 6667                                  |
| `-u`            | `--username`         | 用户名                                                                 | 否                                | root                                  |
| `-pw`           | `--password`         | 密码                                                                   | 否                                | TimechoDB@2021 (V2.0.6.x 版本之前为 root)  |
| `-sql_dialect` | `--sql_dialect`      | 选择 server 是树模型还是表模型，当前支持 tree 和 table 类型            | 否                                | tree                                  |
| `-db`           | `--database`         | 将要导出的目标数据库，只在`-sql_dialect`为 table 类型下生效。      | `-sql_dialect`为 table 时必填 | -                                     |
| `-table`        | `--table`            | 将要导出的目标表，只在`-sql_dialect`为 table 类型下生效。          | 否                               | -                                     |
| `-t`            | `--target`           | 指定输出文件的目标文件夹，如果路径不存在新建文件夹                     | 是                                |                                       |
| `-path`         | `--path_pattern`     | 指定导出元数据的path  pattern                                          | `-sql_dialect`为 tree 时必填  |                                       |
| `-pfn`          | `--prefix_file_name` | 指定导出文件的名称。                                                   | 否                                | dump\_dbname.sql                      |
| `-lpf`          | `--lines_per_file`  | 指定导出的dump文件最大行数，只在`-sql_dialect`为 tree 类型下生效。 | 否                                | `10000`                               |
| `-timeout`      | `--query_timeout`    | 会话查询的超时时间(ms)                                                 | 否                                | -1范围：-1～Long. max=9223372036854775807 |
| `-help`         | `--help`             | 显示帮助信息                                                           | 否                                |                                       |

### 2.2 运行命令

```Bash
Shell
# Unix/OS X
> tools/export-schema.sh [-sql_dialect<sql_dialect>] -db<database> -table<table>  
                [-h <host>] [-p <port>] [-u <username>] [-pw <password>] 
                -t <target_directory> [-path <exportPathPattern>] [-pfn <prefix_file_name>] 
                [-lpf <lines_per_file>] [-timeout <query_timeout>]
# Windows
# V2.0.4.x 版本之前
> tools\export-schema.bat [-sql_dialect<sql_dialect>] -db<database> -table<table>  
                [-h <host>] [-p <port>] [-u <username>] [-pw <password>] 
                -t <target_directory> [-path <exportPathPattern>] [-pfn <prefix_file_name>] 
                [-lpf <lines_per_file>] [-timeout <query_timeout>]
               
# V2.0.4.x 版本及之后               
> tools\windows\schema\export-schema.bat [-sql_dialect<sql_dialect>] -db<database> -table<table>  
                [-h <host>] [-p <port>] [-u <username>] [-pw <password>] 
                -t <target_directory> [-path <exportPathPattern>] [-pfn <prefix_file_name>] 
                [-lpf <lines_per_file>] [-timeout <query_timeout>]
```

### 2.3 运行示例

```Bash
# 导出 root.treedb路径下的元数据
./export-schema.sh -sql_dialect tree -t /home/ -path "root.treedb.**"

# 导出结果内容格式如下
Timeseries,Alias,DataType,Encoding,Compression
root.treedb.device.temperature,,DOUBLE,GORILLA,LZ4
root.treedb.device.humidity,,DOUBLE,GORILLA,LZ4
```