@keyv/bigmap

Bigmap for Keyv

Features

• Based on the Map interface and uses the same API.
• Lightweight with no dependencies.
• Scales to past the 17 million key limit of a regular Map.
• Uses a hash djb2Hash for fast key lookups.
• Ability to use your own hash function.
• Built in Typescript and Generics for type safety.
• Used in @cacheable/memory for scalable in-memory caching.
• Maintained regularly with a focus on performance and reliability.

Table of Contents

• Installation
• Overview
• Basic Usage
• Custom Store Size
• Custom Hash Function
• Iteration
  • For...of Loop
  • forEach
  • Keys, Values, and Entries
• Advanced Features
  • Type Safety with Generics
  • Large-Scale Data
• Using with Keyv
  • createKeyv
  • With Custom Options
  • Type Safety
• Integration with Keyv Ecosystem
• API
  • Constructor
  • Properties
  • Methods
    • set
    • get
    • has
    • delete
    • clear
    • forEach
    • keys
    • values
    • entries
    • Symbol.iterator
    • getStore
    • getStoreMap
    • initStore
  • Types
    • StoreHashFunction
    • defaultHashFunction
    • djb2Hash
• Contributing
• License

Installation

npm install --save keyv @keyv/bigmap
    

Overview

BigMap is a scalable Map implementation that overcomes JavaScript's built-in Map limit of approximately 17 million entries. It uses a distributed hash approach with multiple internal Map instances.

Basic Usage

import { BigMap } from '@keyv/bigmap';
    
    // Create a new BigMap
    const bigMap = new BigMap<string, number>();
    
    // Set values
    bigMap.set('key1', 100);
    bigMap.set('key2', 200);
    
    // Get values
    const value = bigMap.get('key1'); // 100
    
    // Check if key exists
    bigMap.has('key1'); // true
    
    // Delete a key
    bigMap.delete('key1'); // true
    
    // Get size
    console.log(bigMap.size); // 1
    
    // Clear all entries
    bigMap.clear();
    

Custom Store Size

By default, BigMap uses 4 internal Map instances. You can configure this:

const bigMap = new BigMap<string, number>({ storeSize: 10 });
    

Note: Changing the storeSize after initialization will clear all entries.

Custom Hash Function

Provide your own hash function for key distribution:

const customHashFunction = (key: string, storeSize: number) => {
      return key.length % storeSize;
    };
    
    const bigMap = new BigMap<string, string>({
      storeHashFunction: customHashFunction
    });
    

Iteration

BigMap supports all standard Map iteration methods:

For...of Loop

const bigMap = new BigMap<string, number>();
    bigMap.set('a', 1);
    bigMap.set('b', 2);
    
    for (const [key, value] of bigMap) {
      console.log(key, value);
    }
    

forEach

bigMap.forEach((value, key) => {
      console.log(key, value);
    });
    
    // With custom context
    const context = { sum: 0 };
    bigMap.forEach(function(value) {
      this.sum += value;
    }, context);
    

Keys, Values, and Entries

// Iterate over keys
    for (const key of bigMap.keys()) {
      console.log(key);
    }
    
    // Iterate over values
    for (const value of bigMap.values()) {
      console.log(value);
    }
    
    // Iterate over entries
    for (const [key, value] of bigMap.entries()) {
      console.log(key, value);
    }
    

Advanced Features

Type Safety with Generics

interface User {
      id: number;
      name: string;
    }
    
    const userMap = new BigMap<string, User>();
    userMap.set('user1', { id: 1, name: 'Alice' });
    

Large-Scale Data

BigMap is designed to handle millions of entries:

const bigMap = new BigMap<string, number>({ storeSize: 16 });
    
    // Add 20+ million entries without hitting Map limits
    for (let i = 0; i < 20000000; i++) {
      bigMap.set(`key${i}`, i);
    }
    
    console.log(bigMap.size); // 20000000
    

Using with Keyv

BigMap can be used as a storage adapter for Keyv, providing a scalable in-memory store with TTL support.

createKeyv

The createKeyv function creates a Keyv instance with BigMap as the storage adapter.

Parameters:

• options (optional): BigMap configuration options
  • storeSize (number): Number of internal Map instances. Default: 4
  • storeHashFunction (StoreHashFunction): Custom hash function for key distribution

Returns: Keyv instance with BigMap adapter

Example:

import { createKeyv } from '@keyv/bigmap';
    
    // Basic usage
    const keyv = createKeyv();
    
    // Set with TTL (in milliseconds)
    await keyv.set('user:123', { name: 'Alice', age: 30 }, 60000); // Expires in 60 seconds
    
    // Get value
    const user = await keyv.get('user:123');
    console.log(user); // { name: 'Alice', age: 30 }
    
    // Check if key exists
    const exists = await keyv.has('user:123');
    
    // Delete key
    await keyv.delete('user:123');
    
    // Clear all keys
    await keyv.clear();
    

With Custom Options

import { createKeyv } from '@keyv/bigmap';
    
    // Create with custom store size for better performance with millions of keys
    const keyv = createKeyv({ storeSize: 16 });
    
    // With custom hash function
    const keyv = createKeyv({
      storeSize: 8,
      storeHashFunction: (key, storeSize) => {
        // Custom distribution logic
        return key.length % storeSize;
      }
    });
    

Type Safety

import { createKeyv } from '@keyv/bigmap';
    
    interface Product {
      id: string;
      name: string;
      price: number;
    }
    
    const keyv = createKeyv<string, Product>();
    
    await keyv.set('product:1', {
      id: '1',
      name: 'Laptop',
      price: 999
    });
    
    const product = await keyv.get<Product>('product:1');
    

Integration with Keyv Ecosystem

BigMap works seamlessly with the Keyv ecosystem:

import { createKeyv } from '@keyv/bigmap';
    
    const cache = createKeyv({ storeSize: 16 });
    
    // Use with namespaces
    const users = cache.namespace('users');
    const products = cache.namespace('products');
    
    await users.set('123', { name: 'Alice' });
    await products.set('456', { name: 'Laptop' });
    
    // Iterate over keys
    for await (const [key, value] of cache.iterator()) {
      console.log(key, value);
    }
    

API

Constructor

new BigMap(options?)

Creates a new BigMap instance.

Parameters:

• options (optional): Configuration options
  • storeSize (number): Number of internal Map instances to use. Default: 4. Must be at least 1.
  • storeHashFunction (StoreHashFunction): Custom hash function for key distribution. Default: defaultHashFunction

Example:

const bigMap = new BigMap<string, number>();
    const customBigMap = new BigMap<string, number>({
      storeSize: 10,
      storeHashFunction: (key, storeSize) => key.length % storeSize
    });
    

Properties

Examples:

const bigMap = new BigMap<string, number>();
    
    // size property
    bigMap.set('key1', 100);
    console.log(bigMap.size); // 1
    
    // storeSize property
    console.log(bigMap.storeSize); // 4 (default)
    bigMap.storeSize = 8; // Changes size and clears all entries
    
    // storeHashFunction property
    bigMap.storeHashFunction = (key, storeSize) => key.length % storeSize;
    
    // store property
    console.log(bigMap.store.length); // 8
    

Methods

set

Sets the value for a key in the map.

Parameters:

• key (K): The key to set
• value (V): The value to associate with the key

Returns: Map - The internal Map instance where the key was stored

Example:

bigMap.set('user123', { name: 'Alice' });
    

get

Gets the value associated with a key.

Parameters:

• key (K): The key to retrieve

Returns: V | undefined - The value, or undefined if not found

Example:

const value = bigMap.get('user123');
    

has

Checks if a key exists in the map.

Parameters:

• key (K): The key to check

Returns: boolean - True if the key exists, false otherwise

Example:

if (bigMap.has('user123')) {
      console.log('User exists');
    }
    

delete

Deletes a key-value pair from the map.

Parameters:

• key (K): The key to delete

Returns: boolean - True if the entry was deleted, false if the key was not found

Example:

const deleted = bigMap.delete('user123');
    

clear

Removes all entries from the map.

Returns: void

Example:

bigMap.clear();
    console.log(bigMap.size); // 0
    

forEach

Executes a provided function once for each key-value pair.

Parameters:

• callbackfn (function): Function to execute for each entry
  • value (V): The value of the current entry
  • key (K): The key of the current entry
  • map (Map): The BigMap instance
• thisArg (optional): Value to use as this when executing the callback

Returns: void

Example:

bigMap.forEach((value, key) => {
      console.log(`${key}: ${value}`);
    });
    
    // With custom context
    const context = { total: 0 };
    bigMap.forEach(function(value) {
      this.total += value;
    }, context);
    

keys

Returns an iterator of all keys in the map.

Returns: IterableIterator

Example:

for (const key of bigMap.keys()) {
      console.log(key);
    }
    

values

Returns an iterator of all values in the map.

Returns: IterableIterator

Example:

for (const value of bigMap.values()) {
      console.log(value);
    }
    

entries

Returns an iterator of all key-value pairs in the map.

Returns: IterableIterator<[K, V]>

Example:

for (const [key, value] of bigMap.entries()) {
      console.log(key, value);
    }
    

Symbol.iterator

Returns an iterator for the map (same as entries()). Enables for...of loops.

Returns: IterableIterator<[K, V]>

Example:

for (const [key, value] of bigMap) {
      console.log(key, value);
    }
    

getStore

Gets the internal Map instance for a specific key.

Parameters:

• key (K): The key to find the store for

Returns: Map - The internal Map instance

Example:

const store = bigMap.getStore('user123');
    

getStoreMap

Gets the internal Map instance at a specific index.

Parameters:

• index (number): The index of the Map to retrieve (0 to storeSize - 1)

Returns: Map - The Map at the specified index

Throws: Error if index is out of bounds

Example:

const firstMap = bigMap.getStoreMap(0);
    

initStore

Initializes the internal store with empty Map instances. Called automatically during construction.

Returns: void

Types

StoreHashFunction

Type definition for custom hash functions.

type StoreHashFunction = (key: string, storeSize: number) => number;
    

Parameters:

• key (string): The key to hash (converted to string)
• storeSize (number): The number of stores (adjusted for zero-based index)

Returns: number - The index of the store to use (0 to storeSize - 1)

defaultHashFunction

The default hash function using DJB2 algorithm.

Example:

import { defaultHashFunction } from '@keyv/bigmap';
    
    const index = defaultHashFunction('myKey', 4);
    

djb2Hash

DJB2 hash algorithm implementation.

Parameters:

• string (string): The string to hash
• min (number): Minimum value. Default: 0
• max (number): Maximum value. Default: 10

Returns: number - Hash value within the specified range

Example:

import { djb2Hash } from '@keyv/bigmap';
    
    const hash = djb2Hash('myKey', 0, 10);
    

Contributing

Please see our contributing guide.

License

MIT © Jared Wray