query mysql db with golang

main.go

package main

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

	_ "github.com/go-sql-driver/mysql"
)

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU())
	// defer profile.Start(profile.CPUProfile, profile.ProfilePath(".")).Stop()
	dbRead, err := connectDB("test:test@tcp(127.0.0.1:3306)/test_oltp?charset=utf8&readTimeout=600s&writeTimeout=600s")
	if err != nil {
		fmt.Printf("Error happend when connecting to DB. %s\n", err.Error())
		return
	}
	defer dbRead.Close()
	dbRead.SetMaxIdleConns(0)
	dbRead.SetMaxOpenConns(100)

	query := fmt.Sprintf("WHERE company_id in (11,22,33,44,55,66,77,88,99,00,111,222,333,4444,555,666,777,888,999)")

	relations := getRelations(dbRead, query)
}
func connectDB(addr string) (*sql.DB, error) {
	db, err := sql.Open("mysql", addr)
	if err != nil {
		return nil, err
	}
	if err = db.Ping(); err != nil {
		return nil, err
	}
	return db, nil
}

type Relation struct {
	childId  int64 
	parentId int64 
}

func getRelations(db *sql.DB, where string)[]Relation {
	begin := time.Now()

	var err error
	var rows *sql.Rows
	query := fmt.Sprintf("SELECT `child_id`, `parent_id` FROM `test_relations` %s", where)
	rows, err = db.Query(query)
	if err != nil {
		fmt.Println("query error:", err.Error())
		return nil
	}
	defer rows.Close()

	columns, err := rows.Columns()
	buffer := make([]sql.RawBytes, len(columns))
	scanArgs := make([]interface{}, len(buffer))
	for i := range scanArgs {
		scanArgs[i] = &buffer[i]
	}

	relations := []Relation{}
	relation := Relation{}
	for rows.Next() {
		if err = rows.Scan(scanArgs...); err != nil {
			fmt.Println("scan:", err.Error())
			return nil
		}
		relation.parentId, _ = strconv.ParseInt(string(buffer[1]), 10, 64)
		relation.childId, _ = strconv.ParseInt(string(buffer[0]), 10, 64)

		relations = append(relations, relation)
	}

	if err = rows.Err(); err != nil {
		fmt.Println("next error:", err.Error())
		return nil
	}
	fmt.Printf(">>> getRelations cost: %s\n", time.Since(begin).String())
	return relations
}