英文:
Marshall a Map into BSON by always retaining the same order
问题
我有一个地图，它是由一个字符串切片创建的。然后，我想将其编组为bson格式，以便将其作为索引插入到mongodb中。然而，由于在Golang中创建地图的方式，每次都会得到不同顺序的索引（有时是abc，有时是bac，cba...）。
如何确保创建的编组索引始终按相同的顺序？
fields := []string{"a", "b", "c"}
compoundIndex := make(map[string]int)
for _, field := range fields {
compoundIndex[field] = 1
}
data, err := bson.Marshal(compoundIndex)
fmt.Println(string(data)) // 此输出总是与期望的abc顺序不同
英文:
I have a map, which I create from a slice of strings. I then want to marshal this into bson format, to insert into mongodb as an index. However, because of how maps are created in Golang, I get a different ordering of the index each time (sometimes its abc, othertimes its bac, cba...).
How can I ensure that the marshalled index created is always in the same order?
fields := ["a", "b", "c"]
compoundIndex := make(map[string]int)
for _, field := range fields {
compoundIndex[field] = 1
}
data, err := bson.Marshal(compoundIndex)
fmt.Println(string(data)) // This output is always in a different order than the desired abc
答案1
得分: 2
使用有序的文档表示，bson.D：
var compoundIndex bson.D
for _, field := range fields {
compoundIndex = append(compoundIndex, bson.E{Key: field, Value: 1})
}
data, err := bson.Marshal(compoundIndex)
fmt.Println(string(data)) // 元素总是以相同的顺序打印。
英文:
Use an ordered representation of a document, bson.D:
var compoundIndex bson.D
for _, field := range fields {
compoundIndex = append(compoundIndex, bson.E{Key: field, Value: 1})
}
data, err := bson.Marshal(compoundIndex)
fmt.Println(string(data)) // The elements are always printed in the same order.
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