看到标题,第一反应,map肯定秒杀slice啊,我当时也是这么想的,毕竟前者的查询复杂度是O(1),后者是O(n)。
但是,事事难预料哦,用代码来说明问题:
先写两个测试函数
var testTimeSlice=[]string{"aa","bb","cc","dd","ee","aa","zz"}
var testTimeMap = map[string]bool{"aa": true, "bb": true, "cc": true, "dd": true, "ee": true, "ff": true, "zz": true}
//以上为第一组查询测试数据
var testTimeSlice2=[] string{"aa","bb","cc","dd","ee","aa","aa","bb","cc","dd","ee","aa","aa","bb","cc","dd","ee","aa","aa","bb","cc","dd","ee","aa","i","j", "l", "m", "n", "o", "p", "q", "k", "x", "y", "z",
"1", "2", "3", "4", "5", "6", "7", "8", "9", "10","zz"}
var testTimeMap2 = map[string]bool{"aa": true, "bb": true, "cc": true, "dd": true, "ee": true, "ff": true, "qq": true,"ww": true, "rr": true, "tt": true, "zz": true, "uu": true, "ii": true,"oo": true, "pp": true, "lk": true, "kl": true, "jk": true, "kj": true,"hl": true, "lh": true, "fg": true, "gfdd": true, "df": true, "fd": true,
"i": true, "j": true, "l": true, "m": true, "n": true, "o": true, "p": true, "q": true, "k": true, "x": true, "y": true, "z": true,
"1": true, "2": true, "3": true, "4": true, "5": true, "6": true, "7": true, "8": true, "9": true, "10": true}
//以上为第二组查询测试数据
func testSlice(a []string) {
now:=time.Now()
for j:=0; j < 100000; j++{
for _,v:=range a{
if v=="zz"{
break
}
}
}
finish:=time.Since(now)
fmt.Println(finish1)
}
func testMap(a map[string]bool) {
now:=time.Now()
for j:=0; j < 100000; j++{
if _, ok := a["zz"]; ok {
continue
}
}
finish2:=time.Since(now)
fmt.Println("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")
fmt.Println(finish2)
fmt.Println("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")
}
第一个函数接受一个slice,然后进行十万次查询,第二个函数接受一个map,进行十万次查询。
当用第一组测试数据时,结果如下:
1.0011ms //Slice查询耗时
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
6.0038ms //Map查询耗时
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
用第二组测试数据时,结果如下:
8.0038ms //Slice查询耗时
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
2.0019ms //Map查询耗时
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
现在可以得出结论了,当数据量小的时候,slice的查询速度是比map快的,为什么呢,因为golang的map底层是用hash实现的,既然有hash,那就要做映射,那就有hash函数,这个hash函数的开销千万不要忘记,不要一看到map就只记着O(1)
数据集小,直接遍历查找的开销肯定比hash的开销小。
当数据量上去了,map的优势自然而然就出来了。