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# Go 原生接口

## 1. 使用方法
### 1.1 依赖

* golang >= 1.13
* make   >= 3.0
* curl   >= 7.1.1
* thrift 0.15.0
* Linux、Macos 或其他类 unix 系统
* Windows+bash (下载 IoTDB Go client 需要 git ，通过 WSL、cygwin、Git Bash 任意一种方式均可)

### 1.2 安装方法

* 通过 go mod

```sh
# 切换到 GOPATH 的 HOME 路径，启用 Go Modules 功能
export GO111MODULE=on

# 配置 GOPROXY 环境变量
export GOPROXY=https://goproxy.io

# 创建命名的文件夹或目录，并切换当前目录
mkdir session_example && cd session_example

# 保存文件，自动跳转到新的地址
curl -o session_example.go -L https://github.com/apache/iotdb-client-go/raw/main/example/session_example.go

# 初始化 go module 环境
go mod init session_example

# 下载依赖包
go mod tidy

# 编译并运行程序
go run session_example.go
```

* 通过 GOPATH

```sh
# get thrift 0.13.0
go get github.com/apache/thrift@0.13.0

# 递归创建目录
mkdir -p $GOPATH/src/iotdb-client-go-example/session_example

# 切换到当前目录
cd $GOPATH/src/iotdb-client-go-example/session_example

# 保存文件，自动跳转到新的地址
curl -o session_example.go -L https://github.com/apache/iotdb-client-go/raw/main/example/session_example.go

# 初始化 go module 环境
go mod init

# 下载依赖包
go mod tidy

# 编译并运行程序
go run session_example.go
```
* 注意：请勿使用高版本客户端连接低版本服务。

## 2. ITableSession 接口
### 2.1 功能描述

ITableSession 接口定义了与 IoTDB 交互的基本操作，可以执行数据插入、查询操作以及关闭会话等，非线程安全。

### 2.2 方法列表

以下是 ITableSession 接口中定义的方法及其详细说明：

| **方法名**                                             | **描述**                                                       | **参数**                                                            | **返回值**                                   | **返回异常**                            |
| -------------------------------------------------------------- | ---------------------------------------------------------------------- | --------------------------------------------------------------------------- | ---------------------------------------------------- | ----------------------------------------------- |
| `Insert(tablet *Tablet)`                                 | 将一个包含时间序列数据的Tablet 插入到数据库中| `tablet`: 要插入的`Tablet`| `TSStatus`：执行结果的状态，由 common 包定义。 | `errer`：操作过程中的错误（如连接失败）。 |
| `xecuteNonQueryStatement(sql string)`| 执行非查询 SQL 语句，如 DDL (数据定义语言)或 DML (数据操作语言）命令 | `sql`: 要执行的 SQL 语句。| 同上                                               | 同上|
| `ExecuteQueryStatement (sql string, timeoutInMs *int64)` | 执行查询 SQL 语句，并返回查询结果集                                  | `sql`: 要执行的查询 SQL 语句。`timeoutInMs`: 查询超时时间（毫秒） | `SessionDataSet`：查询结果数据集。             | `errer`：操作过程中的错误（如连接失败）。 |
| `Close()`                                                | 关闭会话，释放所持有的资源                                           | 无                                                                        | 无                                                 | `errer`：关闭连接过程中的错误             |

### 2.3 接口展示
1. ITableSession

```go
// ITableSession defines an interface for interacting with IoTDB tables.
// It supports operations such as data insertion, executing queries, and closing the session.
// Implementations of this interface are expected to manage connections and ensure
// proper resource cleanup.
//
// Each method may return an error to indicate issues such as connection errors
// or execution failures.
//
// Since this interface includes a Close method, it is recommended to use
// defer to ensure the session is properly closed.
type ITableSession interface {

        // Insert inserts a Tablet into the database.
        //
        // Parameters:
        //   - tablet: A pointer to a Tablet containing time-series data to be inserted.
        //
        // Returns:
        //   - r: A pointer to TSStatus indicating the execution result.
        //   - err: An error if an issue occurs during the operation, such as a connection error or execution failure.
        Insert(tablet *Tablet) (r *common.TSStatus, err error)

        // ExecuteNonQueryStatement executes a non-query SQL statement, such as a DDL or DML command.
        //
        // Parameters:
        //   - sql: The SQL statement to execute.
        //
        // Returns:
        //   - r: A pointer to TSStatus indicating the execution result.
        //   - err: An error if an issue occurs during the operation, such as a connection error or execution failure.
        ExecuteNonQueryStatement(sql string) (r *common.TSStatus, err error)

        // ExecuteQueryStatement executes a query SQL statement and returns the result set.
        //
        // Parameters:
        //   - sql: The SQL query statement to execute.
        //   - timeoutInMs: A pointer to the timeout duration in milliseconds for the query execution. 
        //
        // Returns:
        //   - result: A pointer to SessionDataSet containing the query results.
        //   - err: An error if an issue occurs during the operation, such as a connection error or execution failure.
        ExecuteQueryStatement(sql string, timeoutInMs *int64) (*SessionDataSet, error)

        // Close closes the session, releasing any held resources.
        //
        // Returns:
        //   - err: An error if there is an issue with closing the IoTDB connection.
        Close() (err error)
}
```

2. 构造 TableSession

* Config 中不需要手动设置 sqlDialect，使用时只需要使用对应的 NewSession 函数

```Go
type Config struct {
   Host            string
   Port            string
   UserName        string
   Password        string
   FetchSize       int32
   TimeZone        string
   ConnectRetryMax int
   sqlDialect      string
   Version         Version
   Database        string
}

type ClusterConfig struct {
   NodeUrls        []string //ip:port
   UserName        string
   Password        string
   FetchSize       int32
   TimeZone        string
   ConnectRetryMax int
   sqlDialect      string
   Database        string
}

// NewTableSession creates a new TableSession instance using the provided configuration.
//
// Parameters:
//   - config: The configuration for the session.
//   - enableRPCCompression: A boolean indicating whether RPC compression is enabled.
//   - connectionTimeoutInMs: The timeout in milliseconds for establishing a connection.
//
// Returns:
//   - An ITableSession instance if the session is successfully created.
//   - An error if there is an issue during session initialization.
func NewTableSession(config *Config, enableRPCCompression bool, connectionTimeoutInMs int) (ITableSession, error)

// NewClusterTableSession creates a new TableSession instance for a cluster setup.
//
// Parameters:
//   - clusterConfig: The configuration for the cluster session.
//   - enableRPCCompression: A boolean indicating whether RPC compression is enabled.
//
// Returns:
//   - An ITableSession instance if the session is successfully created.
//   - An error if there is an issue during session initialization.
func NewClusterTableSession(clusterConfig *ClusterConfig, enableRPCCompression bool) (ITableSession, error)
```

> 注意：
>
> 通过 *NewTableSession 或 NewClusterTableSession* 得到的 TableSession，连接已经建立，不需要额外的 open 操作。

### 2.4 示例代码

```Go
package main

import (
	"flag"
	"log"
	"math/rand"
	"strconv"
	"time"

	"github.com/apache/iotdb-client-go/v2/client"
)

func main() {
	flag.Parse()
	config := &client.Config{
		Host:     "127.0.0.1",
		Port:     "6667",
		UserName: "root",
		Password: "root",
		Database: "test_session",
	}
	session, err := client.NewTableSession(config, false, 0)
	if err != nil {
		log.Fatal(err)
	}
	defer session.Close()

	checkError(session.ExecuteNonQueryStatement("create database test_db"))
	checkError(session.ExecuteNonQueryStatement("use test_db"))
	checkError(session.ExecuteNonQueryStatement("create table t1 (tag1 string tag, tag2 string tag, s1 text field, s2 text field)"))
	insertRelationalTablet(session)
	showTables(session)
	query(session)
}

func getTextValueFromDataSet(dataSet *client.SessionDataSet, columnName string) string {
	if isNull, err := dataSet.IsNull(columnName); err != nil {
		log.Fatal(err)
	} else if isNull {
		return "null"
	}
	v, err := dataSet.GetString(columnName)
	if err != nil {
		log.Fatal(err)
	}
	return v
}

func insertRelationalTablet(session client.ITableSession) {
	tablet, err := client.NewRelationalTablet("t1", []*client.MeasurementSchema{
		{
			Measurement: "tag1",
			DataType:    client.STRING,
		},
		{
			Measurement: "tag2",
			DataType:    client.STRING,
		},
		{
			Measurement: "s1",
			DataType:    client.TEXT,
		},
		{
			Measurement: "s2",
			DataType:    client.TEXT,
		},
	}, []client.ColumnCategory{client.TAG, client.TAG, client.FIELD, client.FIELD}, 1024)
	if err != nil {
		log.Fatal("Failed to create relational tablet {}", err)
	}
	ts := time.Now().UTC().UnixNano() / 1000000
	for row := 0; row < 16; row++ {
		ts++
		tablet.SetTimestamp(ts, row)
		tablet.SetValueAt("tag1_value_"+strconv.Itoa(row), 0, row)
		tablet.SetValueAt("tag2_value_"+strconv.Itoa(row), 1, row)
		tablet.SetValueAt("s1_value_"+strconv.Itoa(row), 2, row)
		tablet.SetValueAt("s2_value_"+strconv.Itoa(row), 3, row)
		tablet.RowSize++
	}
	checkError(session.Insert(tablet))

	tablet.Reset()

	for row := 0; row < 16; row++ {
		ts++
		tablet.SetTimestamp(ts, row)
		tablet.SetValueAt("tag1_value_1", 0, row)
		tablet.SetValueAt("tag2_value_1", 1, row)
		tablet.SetValueAt("s1_value_"+strconv.Itoa(row), 2, row)
		tablet.SetValueAt("s2_value_"+strconv.Itoa(row), 3, row)

		nullValueColumn := rand.Intn(4)
		tablet.SetValueAt(nil, nullValueColumn, row)
		tablet.RowSize++
	}
	checkError(session.Insert(tablet))
}

func showTables(session client.ITableSession) {
	timeout := int64(2000)
	dataSet, err := session.ExecuteQueryStatement("show tables", &timeout)
	defer dataSet.Close()
	if err != nil {
		log.Fatal(err)
	}
	for {
		hasNext, err := dataSet.Next()
		if err != nil {
			log.Fatal(err)
		}
		if !hasNext {
			break
		}
		value, err := dataSet.GetString("TableName")
		if err != nil {
			log.Fatal(err)
		}
		log.Printf("tableName is %v", value)
	}
}

func query(session client.ITableSession) {
	timeout := int64(2000)
	dataSet, err := session.ExecuteQueryStatement("select * from t1", &timeout)
	defer dataSet.Close()
	if err != nil {
		log.Fatal(err)
	}
	for {
		hasNext, err := dataSet.Next()
		if err != nil {
			log.Fatal(err)
		}
		if !hasNext {
			break
		}
		log.Printf("%v %v %v %v", getTextValueFromDataSet(dataSet, "tag1"), getTextValueFromDataSet(dataSet, "tag2"), getTextValueFromDataSet(dataSet, "s1"), getTextValueFromDataSet(dataSet, "s2"))
	}
}

func checkError(err error) {
	if err != nil {
		log.Fatal(err)
	}
}
```

## 3. TableSessionPool 接口
### 3.1 功能描述

TableSessionPool 是一个用于管理 ITableSession 实例的池。这个池可以帮助我们高效地重用连接，并且在不需要时正确地清理资源, 该接口定义了如何从池中获取会话以及如何关闭池的基本操作。

### 3.2  方法列表

| **方法名**   | **描述**                                                     | **返回值**          | **返回异常**              |
| -------------------- | -------------------------------------------------------------------- | --------------------------- | --------------------------------- |
| `GetSession()` | 从池中获取一个 ITableSession 实例，用于与 IoTDB 交互。             | `ITableSession `实例| `error`：获取失败的错误原因 |
| `Close()`      | 关闭会话池，释放任何持有的资源。关闭后，不能再从池中获取新的会话。 | 无                        | 无                              |

### 3.3 接口展示
1. TableSessionPool

```Go
// TableSessionPool manages a pool of ITableSession instances, enabling efficient
// reuse and management of resources. It provides methods to acquire a session
// from the pool and to close the pool, releasing all held resources.
//
// This implementation ensures proper lifecycle management of sessions,
// including efficient reuse and cleanup of resources.

// GetSession acquires an ITableSession instance from the pool.
//
// Returns:
//   - A usable ITableSession instance for interacting with IoTDB.
//   - An error if a session cannot be acquired.
func (spool *TableSessionPool) GetSession() (ITableSession, error) {
        return spool.sessionPool.getTableSession()
}

// Close closes the TableSessionPool, releasing all held resources.
// Once closed, no further sessions can be acquired from the pool.
func (spool *TableSessionPool) Close()
```

2. 构造 TableSessionPool

```Go
type PoolConfig struct {
   Host            string
   Port            string
   NodeUrls        []string
   UserName        string
   Password        string
   FetchSize       int32
   TimeZone        string
   ConnectRetryMax int
   Database        string
   sqlDialect      string
}

// NewTableSessionPool creates a new TableSessionPool with the specified configuration.
//
// Parameters:
//   - conf: PoolConfig defining the configuration for the pool.
//   - maxSize: The maximum number of sessions the pool can hold.
//   - connectionTimeoutInMs: Timeout for establishing a connection in milliseconds.
//   - waitToGetSessionTimeoutInMs: Timeout for waiting to acquire a session in milliseconds.
//   - enableCompression: A boolean indicating whether to enable compression.
//
// Returns:
//   - A TableSessionPool instance.
func NewTableSessionPool(conf *PoolConfig, maxSize, connectionTimeoutInMs, waitToGetSessionTimeoutInMs int,
        enableCompression bool) TableSessionPool
```

> 注意：
>
> * 通过 TableSessionPool 得到的 TableSession，如果已经在创建 TableSessionPool 指定了 Database，使用时可以不再指定 Database。
> * 如果使用过程中通过 use database 指定了其他 database，在 close 放回 TableSessionPool 时会自动恢复为 TableSessionPool 所用的 database。

### 3.4 示例代码

```go
package main

import (
	"log"
	"strconv"
	"sync"
	"sync/atomic"
	"time"

	"github.com/apache/iotdb-client-go/v2/client"
)

func main() {
	sessionPoolWithSpecificDatabaseExample()
	sessionPoolWithoutSpecificDatabaseExample()
	putBackToSessionPoolExample()
}

func putBackToSessionPoolExample() {
	// should create database test_db before executing
	config := &client.PoolConfig{
		Host:     "127.0.0.1",
		Port:     "6667",
		UserName: "root",
		Password: "root",
		Database: "test_db",
	}
	sessionPool := client.NewTableSessionPool(config, 3, 60000, 4000, false)
	defer sessionPool.Close()

	num := 4
	successGetSessionNum := int32(0)
	var wg sync.WaitGroup
	wg.Add(num)
	for i := 0; i < num; i++ {
		dbName := "db" + strconv.Itoa(i)
		go func() {
			defer wg.Done()
			session, err := sessionPool.GetSession()
			if err != nil {
				log.Println("Failed to create database "+dbName+"because ", err)
				return
			}
			atomic.AddInt32(&successGetSessionNum, 1)
			defer func() {
				time.Sleep(6 * time.Second)
				// put back to session pool
				session.Close()
			}()
			checkError(session.ExecuteNonQueryStatement("create database " + dbName))
			checkError(session.ExecuteNonQueryStatement("use " + dbName))
			checkError(session.ExecuteNonQueryStatement("create table table_of_" + dbName + " (tag1 string tag, tag2 string tag, s1 text field, s2 text field)"))
		}()
	}
	wg.Wait()
	log.Println("success num is", successGetSessionNum)

	log.Println("All session's database have been reset.")
	// the using database will automatically reset to session pool's database after the session closed
	wg.Add(5)
	for i := 0; i < 5; i++ {
		go func() {
			defer wg.Done()
			session, err := sessionPool.GetSession()
			if err != nil {
				log.Println("Failed to get session because ", err)
			}
			defer session.Close()
			timeout := int64(3000)
			dataSet, err := session.ExecuteQueryStatement("show tables", &timeout)
			for {
				hasNext, err := dataSet.Next()
				if err != nil {
					log.Fatal(err)
				}
				if !hasNext {
					break
				}
				value, err := dataSet.GetString("TableName")
				if err != nil {
					log.Fatal(err)
				}
				log.Println("table is", value)
			}
			dataSet.Close()
		}()
	}
	wg.Wait()
}

func sessionPoolWithSpecificDatabaseExample() {
	// should create database test_db before executing
	config := &client.PoolConfig{
		Host:     "127.0.0.1",
		Port:     "6667",
		UserName: "root",
		Password: "root",
		Database: "test_db",
	}
	sessionPool := client.NewTableSessionPool(config, 3, 60000, 8000, false)
	defer sessionPool.Close()
	num := 10
	var wg sync.WaitGroup
	wg.Add(num)
	for i := 0; i < num; i++ {
		tableName := "t" + strconv.Itoa(i)
		go func() {
			defer wg.Done()
			session, err := sessionPool.GetSession()
			if err != nil {
				log.Println("Failed to create table "+tableName+"because ", err)
				return
			}
			defer session.Close()
			checkError(session.ExecuteNonQueryStatement("create table " + tableName + " (tag1 string tag, tag2 string tag, s1 text field, s2 text field)"))
		}()
	}
	wg.Wait()
}

func sessionPoolWithoutSpecificDatabaseExample() {
	config := &client.PoolConfig{
		Host:     "127.0.0.1",
		Port:     "6667",
		UserName: "root",
		Password: "root",
	}
	sessionPool := client.NewTableSessionPool(config, 3, 60000, 8000, false)
	defer sessionPool.Close()
	num := 10
	var wg sync.WaitGroup
	wg.Add(num)
	for i := 0; i < num; i++ {
		dbName := "db" + strconv.Itoa(i)
		go func() {
			defer wg.Done()
			session, err := sessionPool.GetSession()
			if err != nil {
				log.Println("Failed to create database ", dbName, err)
				return
			}
			defer session.Close()
			checkError(session.ExecuteNonQueryStatement("create database " + dbName))
			checkError(session.ExecuteNonQueryStatement("use " + dbName))
			checkError(session.ExecuteNonQueryStatement("create table t1 (tag1 string tag, tag2 string tag, s1 text field, s2 text field)"))
		}()
	}
	wg.Wait()
}

func checkError(err error) {
	if err != nil {
		log.Fatal(err)
	}
}
```