We often created a map with
To get the IndexMap package:
go get -u "github.com/yah01/indexmap"Import the package:
import "github.com/yah01/indexmap"First, to create a IndexMap with primary index:
type Person struct {
ID int64
Name string
Age int
City string
Like []string
}
persons := indexmap.NewIndexMap(indexmap.NewPrimaryIndex(func(value *Person) int64 {
return value.ID
}))Now it's just like the common map type, but then you can add index to seek person with the other field:
persons.AddIndex("name", indexmap.NewSecondaryIndex(func(value *Person) []any {
return []any{value.Name}
}))You have to provide the way to extract keys for the inserted object, all keys must be comparable.
The insertion updates indexes automatically:
ashe := &Person{
ID: 1,
Name: "Ashe",
Age: 39,
City: "San Francisco",
Like: []string{"Bob", "Cassidy"},
}
bob := &Person{
ID: 2,
Name: "Bob",
Age: 18,
City: "San Francisco",
}
cassidy := &Person{
ID: 3,
Name: "Cassidy",
Age: 40,
City: "Shanghai",
Like: []string{"Ashe", "Bob"},
}
persons.Insert(ashe)
persons.Insert(bob)
persons.Insert(cassidy)Adding index after inserting data also works:
persons.AddIndex("city", indexmap.NewSecondaryIndex(func(value *Person) []any {
return []any{value.City}
}))
// Like is a "contain" index
persons.AddIndex("like", indexmap.NewSecondaryIndex(func(value *Person) []any {
like := make([]any, 0, len(value.Like))
for i := range value.Like {
like = append(like, value.Like[i])
}
return like
}))And seek data with primary index or the added index:
fmt.Println("Search with ID or Name:")
fmt.Printf("%+v\n", persons.Get(ashe.ID))
fmt.Printf("%+v\n", persons.GetBy("name", ashe.Name))
fmt.Println("\nSearch persons come from San Francisco:")
for _, person := range persons.GetAllBy("city", "San Francisco") {
fmt.Printf("%+v\n", person)
}
fmt.Println("\nSearch persons like Bob")
for _, person := range persons.GetAllBy("like", "Bob") {
fmt.Printf("%+v\n", person)
}which outputs:
Search with ID or Name:
&{ID:1 Name:Ashe Age:39 City:San Francisco Like:[Bob Cassidy]}
&{ID:1 Name:Ashe Age:39 City:San Francisco Like:[Bob Cassidy]}
Search persons come from San Francisco:
&{ID:1 Name:Ashe Age:39 City:San Francisco Like:[Bob Cassidy]}
&{ID:2 Name:Bob Age:18 City:San Francisco Like:[]}
Search persons like Bob
&{ID:3 Name:Cassidy Age:40 City:Shanghai Like:[Ashe Bob]}
&{ID:1 Name:Ashe Age:39 City:San Francisco Like:[Bob Cassidy]}Inserting the different values with the same key works like the normal map type, the last one overwrites the others, but for a inserted value, modifing it outside may confuse the index, modify an internal value with Update()/UpdateBy():
// DO NOT:
person := persons.GetBy("name", "Ashe")
person.City = "Shanghai"
persons.Insert(person)
// Modify the internal value with Update()/UpdateBy()
persons.UpdateBy("name", "Ashe", func(value *Person) (*Person, bool) {
if value.City == "Shanghai" {
return value, false
}
value.City = "Shanghai"
return value, true
})You can serialize an IndexMap to JSON, the result is the same as serializing a normal map type, doesn't contain the index information, so you can't recover the indexes from that:
// Serialize
imapData, err := json.Marshal(imap)
// Deserialize
// You have to create an IndexMap with primary index,
// it's acceptable to add secondary index after deserializing
imap := NewIndexMap(NewPrimaryIndex(func(value *Person) int64 {
return value.ID
}))
err := json.Unmarshal(imapData, &imap)Like sync.Map, you can iterate the IndexMap with Range() method:
imap.Range(func(key int64, value *Person) bool {
fmt.Printf("key=%v, value=%+v\n", key, value)
return true
})An useful method to get all keys and values:
keys, values := imap.Collect()Let
| Operation | Complexity |
|---|---|
| Get | |
| GetBy | |
| Insert | |
| Update | |
| Remove | |
| AddIndex |
The more indexes, the slower the write operations.