# @keyv/bigmap [
](https://github.com/jaredwra/keyv)
> Bigmap for Keyv
[](https://github.com/jaredwray/keyv/actions/workflows/tests.yaml)
[](https://codecov.io/gh/jaredwray/keyv)
[](https://www.npmjs.com/package/@keyv/bigmap)
[](https://npmjs.com/package/@keyv/bigmap)
# 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
- [Features](#features)
- [Installation](#installation)
- [Overview](#overview)
- [Basic Usage](#basic-usage)
- [Custom Store Size](#custom-store-size)
- [Custom Hash Function](#custom-hash-function)
- [Iteration](#iteration)
- [For...of Loop](#forof-loop)
- [forEach](#foreach)
- [Keys, Values, and Entries](#keys-values-and-entries)
- [Advanced Features](#advanced-features)
- [Type Safety with Generics](#type-safety-with-generics)
- [Large-Scale Data](#large-scale-data)
- [Using with Keyv](#using-with-keyv)
- [createKeyv](#createkeyv)
- [With Custom Options](#with-custom-options)
- [Type Safety](#type-safety)
- [Integration with Keyv Ecosystem](#integration-with-keyv-ecosystem)
- [API](#api)
- [Constructor](#constructor)
- [Properties](#properties)
- [Methods](#methods)
- [set](#set)
- [get](#get)
- [has](#has)
- [delete](#delete)
- [clear](#clear)
- [forEach](#foreach)
- [keys](#keys)
- [values](#values)
- [entries](#entries)
- [Symbol.iterator](#symboliterator)
- [getStore](#getstorekey)
- [getStoreMap](#getstoremapindex)
- [initStore](#initstore)
- [Types](#types)
- [StoreHashFunction](#storehashfunction)
- [defaultHashFunction(key, storeSize)](#defaulthashfunctionkey-storesize)
- [Contributing](#contributing)
- [License](#license)
# Installation
```bash
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
```typescript
import { BigMap } from '@keyv/bigmap';
// Create a new BigMap
const bigMap = new BigMap();
// 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:
```typescript
const bigMap = new BigMap({ storeSize: 10 });
```
**Note:** Changing the `storeSize` after initialization will clear all entries.
# Custom Hash Function
Provide your own hash function for key distribution:
```typescript
const customHashFunction = (key: string, storeSize: number) => {
return key.length % storeSize;
};
const bigMap = new BigMap({
storeHashFunction: customHashFunction
});
```
## Using Hashery for Hash Functions
[Hashery](https://github.com/jaredwray/hashery) is a powerful hashing library that provides multiple hash algorithms. You can use it for better key distribution and it is available as an export:
```typescript
import { BigMap, Hashery } from '@keyv/bigmap';
const hashery = new Hashery();
// Using Hashery's toNumberSync for deterministic key distribution
const bigMap = new BigMap({
storeHashFunction: (key: string, storeSize: number) => {
return hashery.toNumberSync(key, { min: 0, max: storeSize - 1 });
}
});
// You can also use different algorithms
const hasheryFnv1 = new Hashery({ defaultAlgorithmSync: 'fnv1' });
const bigMapWithFnv1 = new BigMap({
storeHashFunction: (key: string, storeSize: number) => {
return hasheryFnv1.toNumberSync(key, { min: 0, max: storeSize - 1 });
}
});
```
Hashery supports multiple synchronous hash algorithms:
- **djb2** - Fast hash function (default)
- **fnv1** - Excellent distribution for hash tables
- **murmer** - MurmurHash algorithm
- **crc32** - Cyclic Redundancy Check
# Iteration
BigMap supports all standard Map iteration methods:
## For...of Loop
```typescript
const bigMap = new BigMap();
bigMap.set('a', 1);
bigMap.set('b', 2);
for (const [key, value] of bigMap) {
console.log(key, value);
}
```
## forEach
```typescript
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
```typescript
// 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
```typescript
interface User {
id: number;
name: string;
}
const userMap = new BigMap();
userMap.set('user1', { id: 1, name: 'Alice' });
```
## Large-Scale Data
BigMap is designed to handle millions of entries:
```typescript
const bigMap = new BigMap({ 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](https://github.com/jaredwray/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:**
```typescript
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
```typescript
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
```typescript
import { createKeyv } from '@keyv/bigmap';
interface Product {
id: string;
name: string;
price: number;
}
const keyv = createKeyv();
await keyv.set('product:1', {
id: '1',
name: 'Laptop',
price: 999
});
const product = await keyv.get('product:1');
```
# Integration with Keyv Ecosystem
BigMap works seamlessly with the Keyv ecosystem:
```typescript
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:**
```typescript
const bigMap = new BigMap();
const customBigMap = new BigMap({
storeSize: 10,
storeHashFunction: (key, storeSize) => key.length % storeSize
});
```
## Properties
| Property | Type | Access | Description |
|----------|------|--------|-------------|
| `size` | `number` | Read-only | Gets the total number of entries in the BigMap. |
| `storeSize` | `number` | Read/Write | Gets or sets the number of internal Map instances. **Note:** Setting this will clear all entries. Default: `4` |
| `storeHashFunction` | `StoreHashFunction \| undefined` | Read/Write | Gets or sets the hash function used for key distribution. |
| `store` | `Array>` | Read-only | Gets the internal array of Map instances. |
**Examples:**
```typescript
const bigMap = new BigMap();
// 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:**
```typescript
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:**
```typescript
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:**
```typescript
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:**
```typescript
const deleted = bigMap.delete('user123');
```
### clear
Removes all entries from the map.
**Returns:** `void`
**Example:**
```typescript
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:**
```typescript
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:**
```typescript
for (const key of bigMap.keys()) {
console.log(key);
}
```
### values
Returns an iterator of all values in the map.
**Returns:** `IterableIterator`
**Example:**
```typescript
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:**
```typescript
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:**
```typescript
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:**
```typescript
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:**
```typescript
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.
```typescript
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 from [Hashery](https://npmjs.com/package/hashery):
**Example:**
```typescript
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:**
```typescript
import { djb2Hash } from '@keyv/bigmap';
const hash = djb2Hash('myKey', 0, 10);
```
# Contributing
Please see our [contributing](https://github.com/jaredwray/keyv/blob/main/CONTRIBUTING.md) guide.
# License
[MIT © Jared Wray](LICENSE)