gorm不并发安全

module mygo

go 1.16

require (
    gorm.io/driver/mysql v1.3.6
    gorm.io/gorm v1.23.8
)

package main

import (
    "log"
    "os"
    "strconv"
    "sync"

    "golang.org/x/sync/errgroup"
    "gorm.io/driver/mysql"
    "gorm.io/gorm"
    "gorm.io/gorm/clause"
    "gorm.io/gorm/logger"
)

func main() {
    conn, _ := gorm.Open(mysql.Open("root:@tcp(127.0.0.1:3306)/test?charset=utf8&parseTime=True&loc=Local"), &gorm.Config{
        Logger: logger.New(log.New(os.Stdout, "\r\n", log.LstdFlags), logger.Config{
            LogLevel: logger.Info,
        }),
    })

    Case1(conn)
    //Case2(conn)
    //Case3(conn)
    //Case4(conn)
}

// Case1 : 查询条件污染
func Case1(conn *gorm.DB) {
    query := conn.Where("id = ?", 1)
    eg := errgroup.Group{}
    for i := 0; i < 3; i++ {
        i := i
        eg.Go(func() error {
            m := &Student{}
            return query.Where("id = ?", i).Find(m).Error
        })
    }

    if err := eg.Wait(); err != nil {
        panic(err)
    }
}

Error 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT * FROM `students` students` WHERE id = id = SELECT * FROM `students` WHER' at line 1
[2.944ms] [rows:0] SELECT * FROM SELECT * FROM `students` students` WHERE id = id = SELECT * FROM `students` WHERE id = 1 AND id = 1 AND id = 2 AND id = 01 AND id = 2 AND id = 0

// Case2 : 查询条件丢失
func Case2(conn *gorm.DB) {
    query := conn.Table("students")
    wg := sync.WaitGroup{}
    for i := 0; i < 10; i++ {
        wg.Add(1)
        go func(id int) { // 0-1000都有数据
            defer wg.Done()
            query.Or("id = ?", id)
        }(i)
    }
    wg.Wait()

    var c int64
    if err := query.Count(&c).Error; err != nil {
        panic(err)
    }
    print(c)
}

[2.017ms] [rows:1] SELECT count(*) FROM `students` WHERE id = 9 OR id = 3 OR id = 8 OR id = 0 OR id = 2 OR id = 5 OR id = 6
6

// Case3 : 并发设置查询条件，导致panic
func Case3(conn *gorm.DB) {
    query := conn.Where("id = ?", 1)
    wg := sync.WaitGroup{}
    for i := 0; i < 64; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            query.Where("id = ?", 1).Where("id = ?", 1).Where("id = ?", 1)
        }()
    }
    wg.Wait()
}

fatal error: concurrent map read and map write

// Case4 : 新建session的同时设置查询条件，导致panic
func Case4(conn *gorm.DB) {
    query := conn.Select("abc").Table("abc").Where("id = ?", 1).
        Joins("cba").Offset(1).Limit(1).Group("111").Order("bbb").
        Clauses(clause.OnConflict{}).Clauses(clause.Locking{})
    wg := sync.WaitGroup{}
    for i := 0; i < 1024; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            query.Session(&gorm.Session{Context: context.Background()})
        }()
        query.Where("id = ?", i) // 没有并发设置查询条件。设置查询条件是串行的
    }
    wg.Wait()
}

fatal error: concurrent map read and map write

func (db *DB) getInstance() *DB {
    if db.clone > 0 {
        tx := &DB{Config: db.Config, Error: db.Error}

        if db.clone == 1 {
            // clone with new statement
            tx.Statement = &Statement{
                DB:       tx,
                ConnPool: db.Statement.ConnPool,
                Context:  db.Statement.Context,
                Clauses:  map[string]clause.Clause{},
                Vars:     make([]interface{}, 0, 8),
            }
        } else {
            // with clone statement
            tx.Statement = db.Statement.clone()
            tx.Statement.DB = tx
        }
        return tx
    }

    return db
}

func (db *DB) getInstance() *DB {
    switch db.clone:
    case 0:
        return db
    case 1:
        return newStatement() // 一个全新的，空白的Statement
    case 2:
        return db.cloneStatement() // 将之前的Statement复制一份
}