buckets

A simple key/value store based on Bolt.

In the parlance of key/value stores, a "bucket" is a collection of unique keys that are associated with values. A buckets database is a set of buckets. The underlying datastore is represented by a single file on disk.

Note that buckets is just an extension of Bolt, providing a Bucket type with some nifty convenience methods for operating on the items (key/value pairs) within instances of it. It streamlines simple transactions (a single put, get, or delete) and working with subsets of items within a bucket (via prefix and range scans).

For example, here's how you put an item in a bucket and get it back out. (Note we're omitting proper error handling here.)

// Open a buckets database.
bx, _ := buckets.Open("data.db")
defer bx.Close()

// Create a new `things` bucket.
things, _ := bx.New([]byte("things"))

// Put key/value into the `things` bucket.
key, value := []byte("A"), []byte("alpha")
things.Put(key, value)

// Read value back in a different read-only transaction.
got, _ := things.Get(key)

fmt.Printf("The value of %q in `things` is %q\n", key, got)

Output:

The value of "A" in `things` is "alpha"

Overview

As noted above, buckets is a wrapper for Bolt, streamlining basic transactions. If you're unfamiliar with Bolt, check out the README and intro articles.

A buckets/bolt database contains a set of buckets. What's a bucket? It's basically just an associative array, mapping keys to values. For simplicity, we say that a bucket contains key/values pairs and we refer to these k/v pairs as "items". You use buckets for storing and retrieving such items.

Since Bolt stores keys in byte-sorted order, we can take advantage of this sorted key namespace for fast prefix and range scanning of keys. In particular, it gives us a way to easily retrieve a subset of items. (See the PrefixItems and RangeItems methods, described below.)

Read/write transactions

• Put(k, v) - save/update item
• PutNX(k, v) - save item if key does not exist
• Delete(k) - delete item
• Insert(items) - save/update items (k/v pairs)
• InsertNX(items) - for each item (k/v pair), save item if key does not exist

Read-only transactions

• Get(k) - get value
• Items() - get list of items (k/v pairs)
• PrefixItems(pre) - get list of items with key prefix
• RangeItems(min, max) - get list of items within key range
• Map(func) - apply func to each item
• MapPrefix(func, pre) - apply func to each item with key prefix
• MapRange(func, min, max) - apply a func to each item within key range

Getting Started

Use go get github.com/joyrexus/buckets to install and see the docs for details.

To open a database, use buckets.Open():

package main

import (
    "log"

    "github.com/joyrexus/buckets"
)

func main() {
    bx, err := buckets.Open("my.db")
    if err != nil {
        log.Fatal(err)
    }
    defer bx.Close()

    ...
}

Note that buckets obtains a file lock on the data file so multiple processes cannot open the same database at the same time.

Examples

The docs contain numerous examples demonstrating basic usage.

See also the examples directory for standalone examples, demonstrating use of buckets for persistence in a web service context.