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btree

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An efficient B-tree implementation in Go.

Features

  • Support for 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 optimization for operations with nearby keys.

Using

To start using this package, install Go and run:

$ go get github.com/tidwall/btree

B-tree types

This package includes the following types of B-trees:

  • btree.Map: A fast B-tree for storing ordered key value pairs.

  • btree.Set: Like Map, but only for storing keys.

  • btree.BTreeG: A feature-rich B-tree for storing data using a custom comparator. Thread-safe.

  • btree.BTree: Like BTreeG but uses the interface{} type for data. Backwards compatible. Thread-safe.

btree.Map

// 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

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

// 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

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

// 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

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

// 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

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 for benchmark numbers.

Contact

Josh Baker @tidwall

License

Source code is available under the MIT License.

btree's People

Contributors

tidwall avatar gconnell avatar keep94 avatar damz avatar 256dpi avatar valardragon avatar gnvk avatar joe2far avatar jonboulle avatar neal avatar

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