如果我知道许多tmp切片的最大大小，那么在创建它们时是否应该设置容量？

Question

If I need to use tmp slices in a function and the function will be called many times, their max capacity will not exceed 10. But the length of them are varied. Just for example, maybe 80% of them only have size of 1. 10% of them have size 3 and 10% of them have size 10.

I can think of an example function like the following:

func getDataFromDb(s []string) []string {
    tmpSlice := make([]string, 0, 10)
    for _, v := range s {
        if check(v) {
            tmpSlice = append(tmpSlice, v)
        }
    }
    ......
    return searchDb(tmpSlice)
}

So should I do var tmpSlice []string, tmpSlice := make([]string, 0, 0), tmpSlice := make([]string, 0, 5), or tmpSlice := make([]string, 0, 10)? or any other suggestions?

Answer 1

I would do

var tmpSlice []string

This would give you an empty string slice and you can append as needed. Unless the slice range gets big and you know the dimension beforehand, otherwise I wouldn't pre-allocate memory for it