tv42 / compound

Go library for making order-preserving keys from structured data, with support for prefix iteration

compound keys as []byte

compound is a Go library that helps you make order-preserving keys from multiple items of data, with support for prefix iteration. It does this even with variable length items of arbitrary data (of the supported data types).

It works like this: first, define your struct

type MyKey struct {
	User string
	Album string
	PhotoID uint64
}

Generate a key for a record:

var key []byte
key = compound.Key(MyKey{User: "jdoe", Album: "Travel", PhotoID: 42})

You can decode a key:

var data MyKey
err := compound.Decode(key, &data)

You can ask for a prefix that matches all keys with specific values:

// iterate an album
prefix := compound.PrefixN(MyKey{User: "jdoe", Album: "Travel"}, 2)

These match all keys with the keys at those exact values. For example, the above will not match an album named "Travel in Europe".

To ask for matching partial values of the last key, use:

prefix := compound.PrefixNPartial(MyKey{User: "jdoe", Album: "Travel in "}, 2)

This does not terminate the last key, letting the above match "Travel in Europe".

Prefixes can also be decoded (not yet implemented):

// for keys from PrefixN
var data MyKey
err := compound.DecodePrefix(key, &data)

// for keys from PrefixNPartial
var data MyKey
err := compound.DecodePrefixPartial(key, &data)