radixtree

Package radixtree implements an Adaptive Radix Tree, aka compressed trie or compact prefix tree. This data structure is useful to quickly lookup data by key, find values whose keys have a common prefix, or find values whose keys are a prefix (i.e. found along the way) of a search key.

It is adaptive in the sense that nodes are not constant size, having only as many children, up to the maximum, as needed to branch to all subtrees. This package implements a radix-256 tree where each key symbol (radix) is a byte, allowing up to 256 possible branches to traverse to the next node.

The implementation is optimized for read performance and does not allocate heap memory for read operation (Get, Iter, IterPath, etc.). Once a radix tree is built, it can be repeatedly searched quickly. Concurrent searches are safe since these do not modify the data structure. Access is not synchronized (not concurrent safe with writes), allowing the caller to synchronize, if needed, in whatever manner works best for the application.

This radix tree offers the following features:

• Efficient: Operations are O(key-len). Zero memory allocation for reading items or iteration.
• Ordered iteration: Iterating the tree is done in lexical order, making the output deterministic.
• Store nil values: Read operations differentiate between missing and nil values.
• Compact: When values are stored using keys that have a common prefix, the common part of the key is only stored once. Consider this when keys are similar to a timestamp, OID, filepath, geohash, network address, etc. Only the minimum number of nodes are kept to branch at the points where keys differ.
• Iterators: Go 1.23 iterators allow ranging over key-value pairs stored in the tree. Iterators can traverse all key-value pairs, pairs with a key having specified prefix, or pairs along a key-path from root to a specified key.
• A Stepper type of iterator traverses the tree one specified byte at a time, and is useful for incremental lookup. A Stepper can be copied in order to branch a search and iterate the copies concurrently.
• Generics: The tree stores the specified type of value without needing to do interface type assertion.

Install

$ go get github.com/gammazero/radixtree

Example

package main

import (
    "fmt"
    "github.com/gammazero/radixtree"
)

func main() {
    rt := radixtree.New()
    rt.Put("tomato", "TOMATO")
    rt.Put("tom", "TOM")
    rt.Put("tommy", "TOMMY")
    rt.Put("tornado", "TORNADO")

    val, found := rt.Get("tom")
    if found {
        fmt.Println("Found", val)
    }
    // Output: Found TOM

    // Find all items whose keys start with "tom".
    for key, value := range rt.IterAt("tom") {
        fmt.Println(key, "=", value)
    }
    // Output:
    // tom = TOM
    // tomato = TOMATO
    // tommy = TOMMY

    // Find all items whose keys are a prefix of "tomato"
    for _, value := range rt.IterPath("tomato") {
        fmt.Println(value)
    }
    // Output:
    // TOM
    // TOMATO

    if rt.Delete("tom") {
        fmt.Println("Deleted tom")
    }
    // Output: Deleted tom

    val, found = rt.Get("tom")
    if found {
        fmt.Println("Found", val)
    } else {
        fmt.Println("not found")
    }
    // Output: not found
}

License

MIT License