I reimplement my project with golang recently. The project was implemented with C++. When I finished the code and have a performance test. I'm shocked by the result. When I query the database with C++, I can get the 130 million rows result in 5 mins. But with golang, it's almost 45 mins. But when I separate the code from the project and build the code snippet, it's finished in 2mins. Why does they have so much huge difference performance result?
My code snippet :
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())
// output :>>> getRelations cost:1m45.791047s
return relations
// len(relations): 131123541
}
75.67s of 96.82s total (78.16%)
Dropped 109 nodes (cum <= 0.48s)
Showing top 20 nodes out of 82 (cum >= 12.04s)
flat flat% sum% cum cum%
11.85s 12.24% 12.24% 11.85s 12.24% runtime.memmove
10.28s 10.62% 22.86% 20.01s 20.67% runtime.mallocgc
5.82s 6.01% 28.87% 5.82s 6.01% strconv.ParseUint
5.79s 5.98% 34.85% 5.79s 5.98% runtime.futex
3.42s 3.53% 38.38% 10.28s 10.62% github.com/go-sql-driver/mysql.(*buffer).readNext
3.42s 3.53% 41.91% 6.38s 6.59% runtime.scang
3.37s 3.48% 45.39% 36.97s 38.18% github.com/go-sql-driver/mysql.(*textRows).readRow
3.37s 3.48% 48.87% 3.37s 3.48% runtime.memclr
3.20s 3.31% 52.18% 3.20s 3.31% runtime.heapBitsSetType
3.02s 3.12% 55.30% 7.36s 7.60% database/sql.convertAssign
2.96s 3.06% 58.36% 3.02s 3.12% runtime.(*mspan).sweep.func1
2.53s 2.61% 60.97% 2.53s 2.61% runtime._ExternalCode
2.39s 2.47% 63.44% 2.96s 3.06% runtime.readgstatus
2.24s 2.31% 65.75% 8.06s 8.32% strconv.ParseInt
2.21s 2.28% 68.03% 5.24s 5.41% runtime.heapBitsSweepSpan
2.15s 2.22% 70.25% 7.68s 7.93% runtime.rawstring
2.06s 2.13% 72.38% 3.18s 3.28% github.com/go-sql-driver/mysql.readLengthEncodedString
1.95s 2.01% 74.40% 12.23s 12.63% github.com/go-sql-driver/mysql.(*mysqlConn).readPacket
1.83s 1.89% 76.29% 79.42s 82.03% main.Relations
1.81s 1.87% 78.16% 12.04s 12.44% runtime.slicebytetostring
(pprof) top20
38.71mins of 42.82mins total (90.40%)
Dropped 334 nodes (cum <= 0.21mins)
Showing top 20 nodes out of 76 (cum >= 1.35mins)
flat flat% sum% cum cum%
12.02mins 28.07% 28.07% 12.48mins 29.15% runtime.addspecial
5.95mins 13.89% 41.96% 15.08mins 35.21% runtime.pcvalue
5.26mins 12.29% 54.25% 5.26mins 12.29% runtime.readvarint
2.60mins 6.08% 60.32% 7.87mins 18.37% runtime.step
1.98mins 4.62% 64.94% 19.45mins 45.43% runtime.gentraceback
1.65mins 3.86% 68.80% 1.65mins 3.86% runtime/internal/atomic.Xchg
1.57mins 3.66% 72.46% 2.93mins 6.84% runtime.(*mspan).sweep
1.52mins 3.54% 76.01% 1.78mins 4.15% runtime.findfunc
1.41mins 3.30% 79.31% 1.42mins 3.31% runtime.markrootSpans
1.13mins 2.64% 81.95% 1.13mins 2.64% runtime.(*fixalloc).alloc
0.64mins 1.50% 83.45% 0.64mins 1.50% runtime.duffcopy
0.46mins 1.08% 84.53% 0.46mins 1.08% runtime.findmoduledatap
0.44mins 1.02% 85.55% 0.44mins 1.02% runtime.fastrand1
0.42mins 0.97% 86.52% 15.49mins 36.18% runtime.funcspdelta
0.38mins 0.89% 87.41% 36.02mins 84.13% runtime.mallocgc
0.30mins 0.7% 88.12% 0.78mins 1.83% runtime.scanobject
0.26mins 0.6% 88.72% 0.32mins 0.74% runtime.stkbucket
0.26mins 0.6% 89.32% 0.26mins 0.6% runtime.memmove
0.23mins 0.55% 89.86% 0.23mins 0.55% runtime.heapBitsForObject
0.23mins 0.53% 90.40% 1.35mins 3.15% runtime.lock
I got my answer and want to share it. This is caused by my mistake. Sometimes ago, I tried to add memory profile and set
runtime. MemProfileRate=1 in my
init method. But I forgot to reset it to a reasonable value. I ignored this method when I checked my code every time. After removing this setting from my project, it returns to normal, and spend almost 5~6mins to query these 130M datas. The speed is pretty close to the C++ version. My advise is that please carefully when you set
runtime.MemProfileRate=1 unless you make sure you want to do that, and remember to reset it back.