homework-jianmu/docs/examples/go/queryreqid/main.go

61 lines
1.8 KiB
Go

package main
import (
"context"
"database/sql"
"fmt"
"log"
"time"
_ "github.com/taosdata/driver-go/v3/taosSql"
)
func main() {
taosDSN := "root:taosdata@tcp(localhost:6030)/"
db, err := sql.Open("taosSql", taosDSN)
if err != nil {
log.Fatalln("Failed to connect to " + taosDSN + ", ErrMessage: " + err.Error())
}
defer db.Close()
initEnv(db)
// ANCHOR: query_id
// use context to set request id
reqId := int64(3)
ctx := context.WithValue(context.Background(), "taos_req_id", reqId)
// execute query with context
querySql := "SELECT ts, current, location FROM power.meters limit 1"
rows, err := db.QueryContext(ctx, querySql)
if err != nil {
log.Fatalf("Failed to execute sql with reqId: %d, url: %s, sql: %s, ErrMessage: %s\n", reqId, taosDSN, querySql, err.Error())
}
for rows.Next() {
// Add your data processing logic here
var (
ts time.Time
current float32
location string
)
err = rows.Scan(&ts, &current, &location)
if err != nil {
log.Fatalf("Failed to scan data, reqId: %d, url:%s, sql: %s, ErrMessage: %s\n", reqId, taosDSN, querySql, err)
}
fmt.Printf("ts: %s, current: %f, location: %s\n", ts, current, location)
}
// ANCHOR_END: query_id
}
func initEnv(conn *sql.DB) {
_, err := conn.Exec("CREATE DATABASE IF NOT EXISTS power")
if err != nil {
log.Fatal("Create database power error: ", err)
}
_, err = conn.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.Fatal("Create stable meters error: ", err)
}
_, err = conn.Exec("INSERT INTO power.d1001 USING power.meters TAGS (2, 'California.SanFrancisco') VALUES (NOW , 10.2, 219, 0.32)")
if err != nil {
log.Fatal("Insert data to power.meters error: ", err)
}
}