TDengine Go Client Library

driver-go is the official Go language client library for TDengine. It implements the database/sql package, the generic Go language interface to SQL databases. Go developers can use it to develop applications that access TDengine cluster data.

Connection types

driver-go provides 3 connection types.

• Native connection, which connects to TDengine instances natively through the TDengine client driver (taosc), supporting data writing, querying, subscriptions, schemaless writing, and bind interface.
• REST connection, which is implemented through taosAdapter. Some features like schemaless and subscriptions are not supported.
• Websocket connection which is implemented through taosAdapter. The set of features implemented by the WebSocket connection differs slightly from those implemented by the native connection.

For a detailed introduction of the connection types, please refer to: Establish Connection

Compatibility

Supports minimum Go version 1.14, it is recommended to use the latest Go version

Supported platforms

Native connections are supported on the same platforms as the TDengine client driver. REST connections are supported on all platforms that can run Go.

Version support

Please refer to version support list

Handling exceptions

If it is a TDengine error, you can get the error code and error information in the following ways.

// import "github.com/taosdata/driver-go/v3/errors"
    if err != nil {
        tError, is := err.(*errors.TaosError)
        if is {
            fmt.Println("errorCode:", int(tError.Code))
            fmt.Println("errorMessage:", tError.ErrStr)
        } else {
            fmt.Println(err.Error())
        }
    }

TDengine DataType vs. Go DataType

TDengine DataType	Go Type
TIMESTAMP	time.Time
TINYINT	int8
SMALLINT	int16
INT	int32
BIGINT	int64
TINYINT UNSIGNED	uint8
SMALLINT UNSIGNED	uint16
INT UNSIGNED	uint32
BIGINT UNSIGNED	uint64
FLOAT	float32
DOUBLE	float64
BOOL	bool
BINARY	string
NCHAR	string
JSON	[]byte

Note: Only TAG supports JSON types

Installation Steps

Pre-installation preparation

• Install Go development environment (Go 1.14 and above, GCC 4.8.5 and above)
• If you use the native connector, please install the TDengine client driver. Please refer to Install Client Driver for specific steps

Configure the environment variables and check the command.

• go env
• gcc -v

Install the client library

1. Initialize the project with the go mod command.

   go mod init taos-demo

2. Introduce taosSql

   import (
     "database/sql"
     _ "github.com/taosdata/driver-go/v3/taosSql"
   )

3. Update the dependency packages with go mod tidy.

   go mod tidy

4. Run the program with go run taos-demo or compile the binary with the go build command.

go run taos-demo
go build

Establishing a connection

Data source names have a standard format, e.g. PEAR DB, but no type prefix (square brackets indicate optionally):

[username[:password]@][protocol[(address)]]/[dbname][?param1=value1&...&paramN=valueN]

DSN in full form.

username:password@protocol(address)/dbname?param=value

native connection

taosSql implements Go's database/sql/driver interface via cgo. You can use the database/sql interface by simply introducing the driver.

Use taosSql as driverName and use a correct DSN as dataSourceName, DSN supports the following parameters.

• cfg specifies the taos.cfg directory

For example:

package main

import (
    "database/sql"
    "fmt"

    _ "github.com/taosdata/driver-go/v3/taosSql"
)

func main() {
    var taosUri = "root:taosdata@tcp(localhost:6030)/"
    taos, err := sql.Open("taosSql", taosUri)
    if err != nil {
        fmt.Println("failed to connect TDengine, err:", err)
        return
    }
}

REST connection

taosRestful implements Go's database/sql/driver interface via http client. You can use the database/sql interface by simply introducing the driver.

Use taosRestful as driverName and use a correct DSN as dataSourceName with the following parameters supported by the DSN.

• disableCompression whether to accept compressed data, default is true do not accept compressed data, set to false if transferring data using gzip compression.
• readBufferSize The default size of the buffer for reading data is 4K (4096), which can be adjusted upwards when the query result has a lot of data.

For example:

package main

import (
    "database/sql"
    "fmt"

    _ "github.com/taosdata/driver-go/v3/taosRestful"
)

func main() {
    var taosUri = "root:taosdata@http(localhost:6041)/"
    taos, err := sql.Open("taosRestful", taosUri)
    if err != nil {
        fmt.Println("failed to connect TDengine, err:", err)
        return
    }
}

WebSocket connection

taosRestful implements Go's database/sql/driver interface via http client. You can use the database/sql interface by simply introducing the driver (driver-go minimum version 3.0.2).

Use taosWS as driverName and use a correct DSN as dataSourceName with the following parameters supported by the DSN.

• writeTimeout The timeout to send data via WebSocket.
• readTimeout The timeout to receive response data via WebSocket.

For example:

package main

import (
    "database/sql"
    "fmt"

    _ "github.com/taosdata/driver-go/v3/taosWS"
)

func main() {
    var taosUri = "root:taosdata@ws(localhost:6041)/"
    taos, err := sql.Open("taosWS", taosUri)
    if err != nil {
        fmt.Println("failed to connect TDengine, err:", err)
        return
    }
}

Specify the URL and Properties to get the connection

The Go client library does not support this feature

Priority of configuration parameters

The Go client library does not support this feature

Usage examples

Create database and tables

_, err = taos.Exec("CREATE DATABASE if not exists power")
if err != nil {
 log.Fatalln("failed to create database, err:", err)
}
_, err = taos.Exec("CREATE STABLE IF NOT EXISTS power.meters (ts TIMESTAMP, current FLOAT, voltage INT, phase FLOAT) TAGS (groupId INT, location BINARY(24))")
if err != nil {
 log.Fatalln("failed to create stable, err:", err)
}

view source code

Insert data

affected, err := taos.Exec("INSERT INTO " +
 "power.d1001 USING power.meters TAGS(2,'California.SanFrancisco') " +
 "VALUES " +
 "(NOW + 1a, 10.30000, 219, 0.31000) " +
 "(NOW + 2a, 12.60000, 218, 0.33000) " +
 "(NOW + 3a, 12.30000, 221, 0.31000) " +
 "power.d1002 USING power.meters TAGS(3, 'California.SanFrancisco') " +
 "VALUES " +
 "(NOW + 1a, 10.30000, 218, 0.25000) ")
if err != nil {
 log.Fatalln("failed to insert data, err:", err)
}
log.Println("affected rows:", affected)

view source code

Querying data

rows, err := taos.Query("SELECT * FROM power.meters")
if err != nil {
 log.Fatalln("failed to select from table, err:", err)
}

defer rows.Close()
for rows.Next() {
 var (
  ts       time.Time
  current  float32
  voltage  int
  phase    float32
  groupId  int
  location string
 )
 err := rows.Scan(&ts, &current, &voltage, &phase, &groupId, &location)
 if err != nil {
  log.Fatalln("scan error:\n", err)
  return
 }
 log.Println(ts, current, voltage, phase, groupId, location)
}

view source code

execute SQL with reqId

The reqId is very similar to TraceID in distributed tracing systems. In a distributed system, a request may need to pass through multiple services or modules to be completed. The reqId is used to identify and associate all related operations of this request, allowing us to track and understand the complete execution path of the request. Here are some primary usage of reqId:

• Request Tracing: By associating the same reqId with all related operations of a request, we can trace the complete path of the request within the system.
• Performance Analysis: By analyzing a request's reqId, we can understand the processing time of the request across various services or modules, thereby identifying performance bottlenecks.
• Fault Diagnosis: When a request fails, we can identify the location of the issue by examining the reqId associated with that request.

If the user does not set a reqId, the client library will generate one randomly internally, but it is still recommended for the user to set it, as it can better associate with the user's request.

ctx := context.WithValue(context.Background(), common.ReqIDKey, common.GetReqID())
_, err = taos.ExecContext(ctx, "CREATE DATABASE IF NOT EXISTS power")
if err != nil {
 log.Fatalln("failed to create database, err:", err)
}

view source code

Writing data via parameter binding

native connection

package main

import (
 "fmt"
 "strconv"
 "time"

 "github.com/taosdata/driver-go/v3/af"
 "github.com/taosdata/driver-go/v3/common"
 "github.com/taosdata/driver-go/v3/common/param"
)

const (
 NumOfSubTable = 10
 NumOfRow      = 10
)

func main() {
 prepare()
 db, err := af.Open("", "root", "taosdata", "power", 0)
 if err != nil {
  panic(err)
 }
 defer db.Close()
 stmt := db.InsertStmt()
 defer stmt.Close()
 err = stmt.Prepare("INSERT INTO ? USING meters TAGS(?,?) VALUES (?,?,?,?)")
 if err != nil {
  panic(err)
 }
 for i := 1; i <= NumOfSubTable; i++ {
  tags := param.NewParam(2).AddInt(i).AddBinary([]byte("location"))
  err = stmt.SetTableNameWithTags("d_bind_"+strconv.Itoa(i), tags)
  if err != nil {
   panic(err)
  }
  now := time.Now()
  params := make([]*param.Param, 4)
  params[0] = param.NewParam(NumOfRow)
  params[1] = param.NewParam(NumOfRow)
  params[2] = param.NewParam(NumOfRow)
  params[3] = param.NewParam(NumOfRow)
  for i := 0; i < NumOfRow; i++ {
   params[0].SetTimestamp(i, now.Add(time.Duration(i)*time.Second), common.PrecisionMilliSecond)
   params[1].SetFloat(i, float32(i))
   params[2].SetInt(i, i)
   params[3].SetFloat(i, float32(i))
  }
  paramTypes := param.NewColumnType(4).AddTimestamp().AddFloat().AddInt().AddFloat()
  err = stmt.BindParam(params, paramTypes)
  if err != nil {
   panic(err)
  }
  err = stmt.AddBatch()
  if err != nil {
   panic(err)
  }
  err = stmt.Execute()
  if err != nil {
   panic(err)
  }
  affected := stmt.GetAffectedRows()
  fmt.Println("affected rows:", affected)
 }
}

func prepare() {
 db, err := af.Open("", "root", "taosdata", "", 0)
 if err != nil {
  panic(err)
 }
 defer db.Close()
 _, err = db.Exec("CREATE DATABASE IF NOT EXISTS power")
 if err != nil {
  panic(err)
 }
 _, err = db.Exec("CREATE STABLE IF NOT EXISTS power.meters (ts TIMESTAMP, current FLOAT, voltage INT, phase FLOAT) TAGS (groupId INT, location BINARY(24))")
 if err != nil {
  panic(err)
 }
}

view source code

WebSocket connection

package main

import (
 "database/sql"
 "fmt"
 "strconv"
 "time"

 "github.com/taosdata/driver-go/v3/common"
 "github.com/taosdata/driver-go/v3/common/param"
 _ "github.com/taosdata/driver-go/v3/taosRestful"
 "github.com/taosdata/driver-go/v3/ws/stmt"
)

const (
 NumOfSubTable = 10
 NumOfRow      = 10
)

func main() {
 prepare()
 config := stmt.NewConfig("ws://127.0.0.1:6041", 0)
 config.SetConnectUser("root")
 config.SetConnectPass("taosdata")
 config.SetConnectDB("power")
 config.SetMessageTimeout(common.DefaultMessageTimeout)
 config.SetWriteWait(common.DefaultWriteWait)
 config.SetErrorHandler(func(connector *stmt.Connector, err error) {
  panic(err)
 })
 config.SetCloseHandler(func() {
  fmt.Println("stmt connector closed")
 })

 connector, err := stmt.NewConnector(config)
 if err != nil {
  panic(err)
 }
 stmt, err := connector.Init()
 err = stmt.Prepare("INSERT INTO ? USING meters TAGS(?,?) VALUES (?,?,?,?)")
 if err != nil {
  panic(err)
 }
 for i := 1; i <= NumOfSubTable; i++ {
  tags := param.NewParam(2).AddInt(i).AddBinary([]byte("location"))
  err = stmt.SetTableName("d_bind_" + strconv.Itoa(i))
  if err != nil {
   panic(err)
  }
  err = stmt.SetTags(tags, param.NewColumnType(2).AddInt().AddBinary(8))
  now := time.Now()
  params := make([]*param.Param, 4)
  params[0] = param.NewParam(NumOfRow)
  params[1] = param.NewParam(NumOfRow)
  params[2] = param.NewParam(NumOfRow)
  params[3] = param.NewParam(NumOfRow)
  for i := 0; i < NumOfRow; i++ {
   params[0].SetTimestamp(i, now.Add(time.Duration(i)*time.Second), common.PrecisionMilliSecond)
   params[1].SetFloat(i, float32(i))
   params[2].SetInt(i, i)
   params[3].SetFloat(i, float32(i))
  }
  paramTypes := param.NewColumnType(4).AddTimestamp().AddFloat().AddInt().AddFloat()
  err = stmt.BindParam(params, paramTypes)
  if err != nil {
   panic(err)
  }
  err = stmt.AddBatch()
  if err != nil {
   panic(err)
  }
  err = stmt.Exec()
  if err != nil {
   panic(err)
  }
  affected := stmt.GetAffectedRows()
  fmt.Println("affected rows:", affected)
 }
}

func prepare() {
 db, err := sql.Open("taosRestful", "root:taosdata@http(localhost:6041)/")
 if err != nil {
  panic(err)
 }
 defer db.Close()
 _, err = db.Exec("CREATE DATABASE IF NOT EXISTS power")
 if err != nil {
  panic(err)
 }
 _, err = db.Exec("CREATE STABLE IF NOT EXISTS power.meters (ts TIMESTAMP, current FLOAT, voltage INT, phase FLOAT) TAGS (groupId INT, location BINARY(24))")
 if err != nil {
  panic(err)
 }
}

view source code

Schemaless Writing

native connection

package main

import (
 "fmt"

 "github.com/taosdata/driver-go/v3/af"
)

const LineDemo = "meters,groupid=2,location=California.SanFrancisco current=10.3000002f64,voltage=219i32,phase=0.31f64 1626006833639000000"

const TelnetDemo = "stb0_0 1707095283260 4 host=host0 interface=eth0"

const JsonDemo = "{\"metric\": \"meter_current\",\"timestamp\": 1626846400,\"value\": 10.3, \"tags\": {\"groupid\": 2, \"location\": \"California.SanFrancisco\", \"id\": \"d1001\"}}"

func main() {
 conn, err := af.Open("localhost", "root", "taosdata", "", 6030)
 if err != nil {
  fmt.Println("fail to connect, err:", err)
 }
 defer conn.Close()
 _, err = conn.Exec("CREATE DATABASE IF NOT EXISTS power")
 if err != nil {
  panic(err)
 }
 _, err = conn.Exec("use power")
 if err != nil {
  panic(err)
 }
 err = conn.InfluxDBInsertLines([]string{LineDemo}, "ns")
 if err != nil {
  panic(err)
 }
 err = conn.OpenTSDBInsertTelnetLines([]string{TelnetDemo})
 if err != nil {
  panic(err)
 }
 err = conn.OpenTSDBInsertJsonPayload(JsonDemo)
 if err != nil {
  panic(err)
 }
}

view source code

WebSocket connection

package main

import (
 "database/sql"
 "log"
 "time"

 "github.com/taosdata/driver-go/v3/common"
 _ "github.com/taosdata/driver-go/v3/taosWS"
 "github.com/taosdata/driver-go/v3/ws/schemaless"
)

const LineDemo = "meters,groupid=2,location=California.SanFrancisco current=10.3000002f64,voltage=219i32,phase=0.31f64 1626006833639000000"

const TelnetDemo = "stb0_0 1707095283260 4 host=host0 interface=eth0"

const JsonDemo = "{\"metric\": \"meter_current\",\"timestamp\": 1626846400,\"value\": 10.3, \"tags\": {\"groupid\": 2, \"location\": \"California.SanFrancisco\", \"id\": \"d1001\"}}"

func main() {
 db, err := sql.Open("taosWS", "root:taosdata@ws(localhost:6041)/")
 if err != nil {
  log.Fatal(err)
 }
 defer db.Close()
 _, err = db.Exec("create database if not exists power")
 if err != nil {
  log.Fatal(err)
 }
 s, err := schemaless.NewSchemaless(schemaless.NewConfig("ws://localhost:6041", 1,
  schemaless.SetDb("power"),
  schemaless.SetReadTimeout(10*time.Second),
  schemaless.SetWriteTimeout(10*time.Second),
  schemaless.SetUser("root"),
  schemaless.SetPassword("taosdata"),
  schemaless.SetErrorHandler(func(err error) {
   log.Fatal(err)
  }),
 ))
 if err != nil {
  panic(err)
 }
 err = s.Insert(LineDemo, schemaless.InfluxDBLineProtocol, "ns", 0, common.GetReqID())
 if err != nil {
  panic(err)
 }
 err = s.Insert(TelnetDemo, schemaless.OpenTSDBTelnetLineProtocol, "ms", 0, common.GetReqID())
 if err != nil {
  panic(err)
 }
 err = s.Insert(JsonDemo, schemaless.OpenTSDBJsonFormatProtocol, "ms", 0, common.GetReqID())
 if err != nil {
  panic(err)
 }
}

view source code

Schemaless with reqId

func (s *Schemaless) Insert(lines string, protocol int, precision string, ttl int, reqID int64) error

You can get the unique id by common.GetReqID().

Data Subscription

The TDengine Go client library supports subscription functionality with the following application API.

Create a Topic

_, err = db.Exec("CREATE TOPIC IF NOT EXISTS topic_meters AS SELECT ts, current, voltage, phase, groupid, location FROM power.meters")
if err != nil {
 panic(err)
}

view source code

Create a Consumer

consumer, err := tmq.NewConsumer(&tmqcommon.ConfigMap{
 "group.id":            "test",
 "auto.offset.reset":   "latest",
 "td.connect.ip":       "127.0.0.1",
 "td.connect.user":     "root",
 "td.connect.pass":     "taosdata",
 "td.connect.port":     "6030",
 "client.id":           "test_tmq_client",
 "enable.auto.commit":  "false",
 "msg.with.table.name": "true",
})
if err != nil {
 panic(err)
}

view source code

Subscribe to consume data

go func() {
 for {
  _, err = db.Exec("insert into power.d001 values (now, 1.1, 220, 0.1)")
  if err != nil {
   panic(err)
  }
  time.Sleep(time.Millisecond * 100)
 }
}()

err = consumer.Subscribe("topic_meters", nil)
if err != nil {
 panic(err)
}

for i := 0; i < 5; i++ {
 ev := consumer.Poll(500)
 if ev != nil {
  switch e := ev.(type) {
  case *tmqcommon.DataMessage:
   fmt.Printf("get message:%v\n", e)
  case tmqcommon.Error:
   fmt.Fprintf(os.Stderr, "%% Error: %v: %v\n", e.Code(), e)
   panic(e)
  }
  consumer.Commit()
 }
}

view source code

Assignment subscription Offset

partitions, err := consumer.Assignment()
if err != nil {
 panic(err)
}
for i := 0; i < len(partitions); i++ {
 fmt.Println(partitions[i])
 err = consumer.Seek(tmqcommon.TopicPartition{
  Topic:     partitions[i].Topic,
  Partition: partitions[i].Partition,
  Offset:    0,
 }, 0)
 if err != nil {
  panic(err)
 }
}
partitions, err = consumer.Assignment()
if err != nil {
 panic(err)
}

view source code

Close subscriptions

err = consumer.Close()
if err != nil {
 panic(err)
}

view source code

Full Sample Code

native connection

package main

import (
 "fmt"
 "os"
 "time"

 "github.com/taosdata/driver-go/v3/af"
 "github.com/taosdata/driver-go/v3/af/tmq"
 tmqcommon "github.com/taosdata/driver-go/v3/common/tmq"
)

func main() {
 db, err := af.Open("", "root", "taosdata", "", 0)
 if err != nil {
  panic(err)
 }
 defer db.Close()
 _, err = db.Exec("create database if not exists power WAL_RETENTION_PERIOD 86400")
 if err != nil {
  panic(err)
 }
 _, err = db.Exec("CREATE STABLE IF NOT EXISTS power.meters (ts TIMESTAMP, current FLOAT, voltage INT, phase FLOAT) TAGS (groupId INT, location BINARY(24))")
 if err != nil {
  panic(err)
 }
 _, err = db.Exec("create table if not exists power.d001 using power.meters tags(1,'location')")
 if err != nil {
  panic(err)
 }
 // ANCHOR: create_topic
 _, err = db.Exec("CREATE TOPIC IF NOT EXISTS topic_meters AS SELECT ts, current, voltage, phase, groupid, location FROM power.meters")
 if err != nil {
  panic(err)
 }
 // ANCHOR_END: create_topic
 // ANCHOR: create_consumer
 consumer, err := tmq.NewConsumer(&tmqcommon.ConfigMap{
  "group.id":            "test",
  "auto.offset.reset":   "latest",
  "td.connect.ip":       "127.0.0.1",
  "td.connect.user":     "root",
  "td.connect.pass":     "taosdata",
  "td.connect.port":     "6030",
  "client.id":           "test_tmq_client",
  "enable.auto.commit":  "false",
  "msg.with.table.name": "true",
 })
 if err != nil {
  panic(err)
 }
 // ANCHOR_END: create_consumer
 // ANCHOR: poll_data
 go func() {
  for {
   _, err = db.Exec("insert into power.d001 values (now, 1.1, 220, 0.1)")
   if err != nil {
    panic(err)
   }
   time.Sleep(time.Millisecond * 100)
  }
 }()

 err = consumer.Subscribe("topic_meters", nil)
 if err != nil {
  panic(err)
 }

 for i := 0; i < 5; i++ {
  ev := consumer.Poll(500)
  if ev != nil {
   switch e := ev.(type) {
   case *tmqcommon.DataMessage:
    fmt.Printf("get message:%v\n", e)
   case tmqcommon.Error:
    fmt.Fprintf(os.Stderr, "%% Error: %v: %v\n", e.Code(), e)
    panic(e)
   }
   consumer.Commit()
  }
 }
 // ANCHOR_END: poll_data
 // ANCHOR: consumer_seek
 partitions, err := consumer.Assignment()
 if err != nil {
  panic(err)
 }
 for i := 0; i < len(partitions); i++ {
  fmt.Println(partitions[i])
  err = consumer.Seek(tmqcommon.TopicPartition{
   Topic:     partitions[i].Topic,
   Partition: partitions[i].Partition,
   Offset:    0,
  }, 0)
  if err != nil {
   panic(err)
  }
 }
 partitions, err = consumer.Assignment()
 if err != nil {
  panic(err)
 }
 // ANCHOR_END: consumer_seek
 for i := 0; i < len(partitions); i++ {
  fmt.Println(partitions[i])
 }
 // ANCHOR: consumer_close
 err = consumer.Close()
 if err != nil {
  panic(err)
 }
 // ANCHOR_END: consumer_close
}

view source code

WebSocket connection

package main

import (
 "database/sql"
 "fmt"
 "os"
 "time"

 "github.com/taosdata/driver-go/v3/common"
 tmqcommon "github.com/taosdata/driver-go/v3/common/tmq"
 _ "github.com/taosdata/driver-go/v3/taosRestful"
 "github.com/taosdata/driver-go/v3/ws/tmq"
)

func main() {
 db, err := sql.Open("taosRestful", "root:taosdata@http(localhost:6041)/")
 if err != nil {
  panic(err)
 }
 defer db.Close()
 _, err = db.Exec("create database if not exists power WAL_RETENTION_PERIOD 86400")
 if err != nil {
  panic(err)
 }
 _, err = db.Exec("CREATE STABLE IF NOT EXISTS power.meters (ts TIMESTAMP, current FLOAT, voltage INT, phase FLOAT) TAGS (groupId INT, location BINARY(24))")
 if err != nil {
  panic(err)
 }
 _, err = db.Exec("create table if not exists power.d001 using power.meters tags(1,'location')")
 if err != nil {
  panic(err)
 }
 // ANCHOR: create_topic
 _, err = db.Exec("CREATE TOPIC IF NOT EXISTS topic_meters AS SELECT ts, current, voltage, phase, groupid, location FROM power.meters")
 if err != nil {
  panic(err)
 }
 // ANCHOR_END: create_topic
 // ANCHOR: create_consumer
 consumer, err := tmq.NewConsumer(&tmqcommon.ConfigMap{
  "ws.url":                "ws://127.0.0.1:6041",
  "ws.message.channelLen": uint(0),
  "ws.message.timeout":    common.DefaultMessageTimeout,
  "ws.message.writeWait":  common.DefaultWriteWait,
  "td.connect.user":       "root",
  "td.connect.pass":       "taosdata",
  "group.id":              "example",
  "client.id":             "example_consumer",
  "auto.offset.reset":     "latest",
 })
 if err != nil {
  panic(err)
 }
 // ANCHOR_END: create_consumer
 // ANCHOR: poll_data
 go func() {
  for {
   _, err = db.Exec("insert into power.d001 values (now, 1.1, 220, 0.1)")
   if err != nil {
    panic(err)
   }
   time.Sleep(time.Millisecond * 100)
  }
 }()

 err = consumer.Subscribe("topic_meters", nil)
 if err != nil {
  panic(err)
 }

 for i := 0; i < 5; i++ {
  ev := consumer.Poll(500)
  if ev != nil {
   switch e := ev.(type) {
   case *tmqcommon.DataMessage:
    fmt.Printf("get message:%v\n", e)
   case tmqcommon.Error:
    fmt.Fprintf(os.Stderr, "%% Error: %v: %v\n", e.Code(), e)
    panic(e)
   }
   consumer.Commit()
  }
 }
 // ANCHOR_END: poll_data
 // ANCHOR: consumer_seek
 partitions, err := consumer.Assignment()
 if err != nil {
  panic(err)
 }
 for i := 0; i < len(partitions); i++ {
  fmt.Println(partitions[i])
  err = consumer.Seek(tmqcommon.TopicPartition{
   Topic:     partitions[i].Topic,
   Partition: partitions[i].Partition,
   Offset:    0,
  }, 0)
  if err != nil {
   panic(err)
  }
 }
 partitions, err = consumer.Assignment()
 if err != nil {
  panic(err)
 }
 // ANCHOR_END: consumer_seek
 for i := 0; i < len(partitions); i++ {
  fmt.Println(partitions[i])
 }
 // ANCHOR: consumer_close
 err = consumer.Close()
 if err != nil {
  panic(err)
 }
 // ANCHOR_END: consumer_close
}

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More sample programs

• sample program

Frequently Asked Questions

1. bind interface in database/sql crashes

   REST does not support parameter binding related interface. It is recommended to use db.Exec and db.Query.

2. error [0x217] Database not specified or available after executing other statements with use db statement

   The execution of SQL command in the REST interface is not contextual, so using use db statement will not work, see the usage restrictions section above.

3. use taosSql without error but use taosRestful with error [0x217] Database not specified or available

   Because the REST interface is stateless, using the use db statement will not take effect. See the usage restrictions section above.

4. readBufferSize parameter has no significant effect after being increased

   Increasing readBufferSize will reduce the number of syscall calls when fetching results. If the query result is smaller, modifying this parameter will not improve performance significantly. If you increase the parameter value too much, the bottleneck will be parsing JSON data. If you need to optimize the query speed, you must adjust the value based on the actual situation to achieve the best query performance.

5. disableCompression parameter is set to false when the query efficiency is reduced

   When set disableCompression parameter to false, the query result will be compressed by gzip and then transmitted, so you have to decompress the data by gzip after getting it.

6. go get command can't get the package, or timeout to get the package

   Set Go proxy go env -w GOPROXY=https://goproxy.cn,direct.

API Reference

Full API see driver-go documentation