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https://github.com/tidwall/btree
B-tree implementation for Go
https://github.com/tidwall/btree
Last synced: 4 days ago
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B-tree implementation for Go
- Host: GitHub
- URL: https://github.com/tidwall/btree
- Owner: tidwall
- License: mit
- Created: 2016-05-23T22:42:55.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2024-06-09T15:46:27.000Z (6 months ago)
- Last Synced: 2024-12-03T05:04:47.020Z (11 days ago)
- Language: Go
- Homepage:
- Size: 185 KB
- Stars: 1,065
- Watchers: 13
- Forks: 83
- Open Issues: 21
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- zero - btree - tree | Go | MIT | (Members)
README
# btree
[](https://godoc.org/github.com/tidwall/btree)
An efficient [B-tree](https://en.wikipedia.org/wiki/B-tree) implementation in Go.
## Features
- Support for [Generics](#generics) (Go 1.18+).
- `Map` and `Set` types for ordered key-value maps and sets,
- Fast bulk loading for pre-ordered data using the `Load()` method.
- `Copy()` method with copy-on-write support.
- [Path hinting](PATH_HINT.md) optimization for operations with nearby keys.
- Allows for array-like operations. ([Counted B-tree](https://www.chiark.greenend.org.uk/~sgtatham/algorithms/cbtree.html))
## Using
To start using this package, install Go and run:
```sh
$ go get github.com/tidwall/btree
```
## B-tree types
This package includes the following types of B-trees:
- [`btree.Map`](#btreemap):
A fast B-tree for storing ordered key value pairs.
- [`btree.Set`](#btreeset):
Like `Map`, but only for storing keys.
- [`btree.BTreeG`](#btreebtreeg):
A feature-rich B-tree for storing data using a custom comparator. Thread-safe.
- [`btree.BTree`](#btreebtree):
Like `BTreeG` but uses the `interface{}` type for data. Backwards compatible. Thread-safe.
### btree.Map
```go
// Basic
Set(key, value) // insert or replace an item
Get(key, value) // get an existing item
Delete(key) // delete an item
Len() // return the number of items in the map
// Iteration
Scan(iter) // scan items in ascending order
Reverse(iter) // scan items in descending order
Ascend(key, iter) // scan items in ascending order that are >= to key
Descend(key, iter) // scan items in descending order that are <= to key.
Iter() // returns a read-only iterator for for-loops.
// Array-like operations
GetAt(index) // returns the item at index
DeleteAt(index) // deletes the item at index
// Bulk-loading
Load(key, value) // load presorted items into tree
```
#### Example
```go
package main
import (
"fmt"
"github.com/tidwall/btree"
)
func main() {
// create a map
var users btree.Map[string, string]
// add some users
users.Set("user:4", "Andrea")
users.Set("user:6", "Andy")
users.Set("user:2", "Andy")
users.Set("user:1", "Jane")
users.Set("user:5", "Janet")
users.Set("user:3", "Steve")
// Iterate over the maps and print each user
users.Scan(func(key, value string) bool {
fmt.Printf("%s %s\n", key, value)
return true
})
fmt.Printf("\n")
// Delete a couple
users.Delete("user:5")
users.Delete("user:1")
// print the map again
users.Scan(func(key, value string) bool {
fmt.Printf("%s %s\n", key, value)
return true
})
fmt.Printf("\n")
// Output:
// user:1 Jane
// user:2 Andy
// user:3 Steve
// user:4 Andrea
// user:5 Janet
// user:6 Andy
//
// user:2 Andy
// user:3 Steve
// user:4 Andrea
// user:6 Andy
}
```
### btree.Set
```go
// Basic
Insert(key) // insert an item
Contains(key) // test if item exists
Delete(key) // delete an item
Len() // return the number of items in the set
// Iteration
Scan(iter) // scan items in ascending order
Reverse(iter) // scan items in descending order
Ascend(key, iter) // scan items in ascending order that are >= to key
Descend(key, iter) // scan items in descending order that are <= to key.
Iter() // returns a read-only iterator for for-loops.
// Array-like operations
GetAt(index) // returns the item at index
DeleteAt(index) // deletes the item at index
// Bulk-loading
Load(key) // load presorted item into tree
```
#### Example
```go
package main
import (
"fmt"
"github.com/tidwall/btree"
)
func main() {
// create a set
var names btree.Set[string]
// add some names
names.Insert("Jane")
names.Insert("Andrea")
names.Insert("Steve")
names.Insert("Andy")
names.Insert("Janet")
names.Insert("Andy")
// Iterate over the maps and print each user
names.Scan(func(key string) bool {
fmt.Printf("%s\n", key)
return true
})
fmt.Printf("\n")
// Delete a couple
names.Delete("Steve")
names.Delete("Andy")
// print the map again
names.Scan(func(key string) bool {
fmt.Printf("%s\n", key)
return true
})
fmt.Printf("\n")
// Output:
// Andrea
// Andy
// Jane
// Janet
// Steve
//
// Andrea
// Jane
// Janet
}
```
### btree.BTreeG
```go
// Basic
Set(item) // insert or replace an item
Get(item) // get an existing item
Delete(item) // delete an item
Len() // return the number of items in the btree
// Iteration
Scan(iter) // scan items in ascending order
Reverse(iter) // scan items in descending order
Ascend(key, iter) // scan items in ascending order that are >= to key
Descend(key, iter) // scan items in descending order that are <= to key.
Iter() // returns a read-only iterator for for-loops.
// Array-like operations
GetAt(index) // returns the item at index
DeleteAt(index) // deletes the item at index
// Bulk-loading
Load(item) // load presorted items into tree
// Path hinting
SetHint(item, *hint) // insert or replace an existing item
GetHint(item, *hint) // get an existing item
DeleteHint(item, *hint) // delete an item
AscendHint(key, iter, *hint)
DescendHint(key, iter, *hint)
SeekHint(key, iter, *hint)
// Copy-on-write
Copy() // copy the btree
```
#### Example
```go
package main
import (
"fmt"
"github.com/tidwall/btree"
)
type Item struct {
Key, Val string
}
// byKeys is a comparison function that compares item keys and returns true
// when a is less than b.
func byKeys(a, b Item) bool {
return a.Key < b.Key
}
// byVals is a comparison function that compares item values and returns true
// when a is less than b.
func byVals(a, b Item) bool {
if a.Val < b.Val {
return true
}
if a.Val > b.Val {
return false
}
// Both vals are equal so we should fall though
// and let the key comparison take over.
return byKeys(a, b)
}
func main() {
// Create a tree for keys and a tree for values.
// The "keys" tree will be sorted on the Keys field.
// The "values" tree will be sorted on the Values field.
keys := btree.NewBTreeG[Item](byKeys)
vals := btree.NewBTreeG[Item](byVals)
// Create some items.
users := []Item{
Item{Key: "user:1", Val: "Jane"},
Item{Key: "user:2", Val: "Andy"},
Item{Key: "user:3", Val: "Steve"},
Item{Key: "user:4", Val: "Andrea"},
Item{Key: "user:5", Val: "Janet"},
Item{Key: "user:6", Val: "Andy"},
}
// Insert each user into both trees
for _, user := range users {
keys.Set(user)
vals.Set(user)
}
// Iterate over each user in the key tree
keys.Scan(func(item Item) bool {
fmt.Printf("%s %s\n", item.Key, item.Val)
return true
})
fmt.Printf("\n")
// Iterate over each user in the val tree
vals.Scan(func(item Item) bool {
fmt.Printf("%s %s\n", item.Key, item.Val)
return true
})
// Output:
// user:1 Jane
// user:2 Andy
// user:3 Steve
// user:4 Andrea
// user:5 Janet
// user:6 Andy
//
// user:4 Andrea
// user:2 Andy
// user:6 Andy
// user:1 Jane
// user:5 Janet
// user:3 Steve
}
```
### btree.BTree
```go
// Basic
Set(item) // insert or replace an item
Get(item) // get an existing item
Delete(item) // delete an item
Len() // return the number of items in the btree
// Iteration
Scan(iter) // scan items in ascending order
Reverse(iter) // scan items in descending order
Ascend(key, iter) // scan items in ascending order that are >= to key
Descend(key, iter) // scan items in descending order that are <= to key.
Iter() // returns a read-only iterator for for-loops.
// Array-like operations
GetAt(index) // returns the item at index
DeleteAt(index) // deletes the item at index
// Bulk-loading
Load(item) // load presorted items into tree
// Path hinting
SetHint(item, *hint) // insert or replace an existing item
GetHint(item, *hint) // get an existing item
DeleteHint(item, *hint) // delete an item
AscendHint(key, iter, *hint)
DescendHint(key, iter, *hint)
SeekHint(key, iter, *hint)
// Copy-on-write
Copy() // copy the btree
```
#### Example
```go
package main
import (
"fmt"
"github.com/tidwall/btree"
)
type Item struct {
Key, Val string
}
// byKeys is a comparison function that compares item keys and returns true
// when a is less than b.
func byKeys(a, b interface{}) bool {
i1, i2 := a.(*Item), b.(*Item)
return i1.Key < i2.Key
}
// byVals is a comparison function that compares item values and returns true
// when a is less than b.
func byVals(a, b interface{}) bool {
i1, i2 := a.(*Item), b.(*Item)
if i1.Val < i2.Val {
return true
}
if i1.Val > i2.Val {
return false
}
// Both vals are equal so we should fall though
// and let the key comparison take over.
return byKeys(a, b)
}
func main() {
// Create a tree for keys and a tree for values.
// The "keys" tree will be sorted on the Keys field.
// The "values" tree will be sorted on the Values field.
keys := btree.New(byKeys)
vals := btree.New(byVals)
// Create some items.
users := []*Item{
&Item{Key: "user:1", Val: "Jane"},
&Item{Key: "user:2", Val: "Andy"},
&Item{Key: "user:3", Val: "Steve"},
&Item{Key: "user:4", Val: "Andrea"},
&Item{Key: "user:5", Val: "Janet"},
&Item{Key: "user:6", Val: "Andy"},
}
// Insert each user into both trees
for _, user := range users {
keys.Set(user)
vals.Set(user)
}
// Iterate over each user in the key tree
keys.Ascend(nil, func(item interface{}) bool {
kvi := item.(*Item)
fmt.Printf("%s %s\n", kvi.Key, kvi.Val)
return true
})
fmt.Printf("\n")
// Iterate over each user in the val tree
vals.Ascend(nil, func(item interface{}) bool {
kvi := item.(*Item)
fmt.Printf("%s %s\n", kvi.Key, kvi.Val)
return true
})
// Output:
// user:1 Jane
// user:2 Andy
// user:3 Steve
// user:4 Andrea
// user:5 Janet
// user:6 Andy
//
// user:4 Andrea
// user:2 Andy
// user:6 Andy
// user:1 Jane
// user:5 Janet
// user:3 Steve
}
```
## Performance
See [tidwall/btree-benchmark](https://github.com/tidwall/btree-benchmark) for benchmark numbers.
## Contact
Josh Baker [@tidwall](http://twitter.com/tidwall)
## License
Source code is available under the MIT [License](/LICENSE).