flexsearch

What is flexsearch?

FlexSearch is a high-performance, full-text search library for JavaScript. It is designed to be fast and efficient, providing a variety of indexing and search capabilities. FlexSearch can be used in both Node.js and browser environments, making it versatile for different types of applications.

What are flexsearch's main functionalities?

Indexing

FlexSearch allows you to create an index and add documents to it. Each document is associated with a unique ID.

const FlexSearch = require('flexsearch');
const index = new FlexSearch();
index.add(1, 'Hello World');
index.add(2, 'Hi there');

Searching

You can perform searches on the indexed documents. The search results will return the IDs of the matching documents.

index.search('Hello', function(results) {
  console.log(results); // [1]
});

Asynchronous Search

FlexSearch supports asynchronous search operations, which can be useful for handling large datasets or integrating with other asynchronous workflows.

index.search('Hello').then(function(results) {
  console.log(results); // [1]
});

Custom Configuration

FlexSearch allows for extensive customization of the indexing and search process. You can configure encoding, tokenization, threshold, and resolution to suit your specific needs.

const customIndex = new FlexSearch({
  encode: 'icase',
  tokenize: 'forward',
  threshold: 0,
  resolution: 3
});
customIndex.add(1, 'Custom configuration example');

Other packages similar to flexsearch

lunr

Lunr.js is a small, full-text search library for use in the browser and Node.js. It provides a simple and easy-to-use API for indexing and searching documents. Compared to FlexSearch, Lunr.js is more lightweight but may not offer the same level of performance and customization.

elasticlunr

Elasticlunr.js is a lightweight full-text search library that is inspired by Lunr.js and Elasticsearch. It offers more features than Lunr.js, such as support for multiple languages and more advanced search capabilities. However, it may still not match the performance and flexibility of FlexSearch.

search-index

Search-Index is a powerful, full-text search library for Node.js and the browser. It provides a wide range of features, including real-time indexing, faceted search, and more. While it offers more advanced features than FlexSearch, it may be more complex to set up and use.

README

World's fastest and most memory efficient full text search library with zero dependencies.

When it comes to raw search speed FlexSearch outperforms every single searching library out there and also provides flexible search capabilities like multi-word matching, phonetic transformations or partial matching. It also has the most memory-efficient index. Keep in mind that updating and/or removing existing items from the index has a significant cost. When your index needs to be updated continuously then BulkSearch may be a better choice. FlexSearch also provides you a non-blocking asynchronous processing model as well as web workers to perform any updates or queries on the index in parallel through dedicated balanced threads.

Installation Guide  •  API Reference  •  Example Options  •  Custom Builds

Comparison:

• Library Query Benchmarks
• Library Relevance Scoring
• Library Memory Consumption

Supported Platforms:

• Browser
• Node.js

All Features:

• Web-Worker Sharding (not available in Node.js)
• Contextual Indexes
• Partial Matching
• Multi-Phrase Search
• Phonetic Mathching
• Relevance-based Scoring
• Auto-Balanced Cache by Popularity
• Suggestions (Results)
• Asynchronous Processing & Concurrency Control
• Customizable: Matcher, Encoder, Tokenizer, Stemmer, Filter

These features are not available in the 50% smaller light version:

• WebWorker
• Asynchronous Processing
• Cache
• Built-in encoders except 'balance' and 'icase' (you can still pass in customs)
• Debug logging
• Methods: index.info()

The light version is just available as compiled version (flexsearch.light.js).

It is also pretty simple to make Custom Builds

Contextual Search

FlexSearch introduce a new scoring mechanism called Contextual Search which was invented by Thomas Wilkerling, the author of this library. A Contextual Search incredibly boost up queries to a complete new level. The basic idea of this concept is to limit relevance by its context instead of calculating relevance through the whole (unlimited) distance. Imagine you add a text block of some sentences to an index ID. Assuming the query includes a combination of first and last word from this text block, are they really relevant to each other? In this way contextual search also improves the results of relevance-based queries on large amount of text data.

Note: This feature is actually not enabled by default.

Web-Worker Support

Workers get its own dedicated memory. Especially for larger indexes, web worker improves speed and available memory a lot. FlexSearch index was tested with a 250 Mb text file including 10 Million words. The indexing was done silently in background by multiple parallel running workers in about 7 minutes. The final index reserves ~ 8.2 Mb memory/space. The search result took ~ 0.25 ms.

Note: It is slightly faster to use no web worker when the index or query isn't too big (index < 500,000 words, query < 25 words).

Compare BulkSearch vs. FlexSearch

Description	BulkSearch	FlexSearch
Access	Read-Write optimized index	Read-Memory optimized index
Memory	Large: ~ 1 Mb per 100,000 words	Tiny: ~ 100 Kb per 100,000 words
Index Type	Bulk of encoded string data divided into chunks	Lexical pre-scored dictionary Contextual-based map
Strength	fast adds / fast updates / fast removals	fast queries memory-efficient index
Weaks	less powerful contextual search less memory efficient (has to be defragmented from time to time)	updating / deleting extisting items from index is slow adding items to the index optimized for super partial matching (mode: "full") is slow
Pagination	Yes	No

Installation

HTML / Javascript

<html>
<head>
    <script src="js/flexsearch.min.js"></script>
</head>
...

Note: Use flexsearch.min.js for production and flexsearch.js for development.

Use latest from CDN:

<script src="https://cdn.rawgit.com/nextapps-de/flexsearch/master/flexsearch.min.js"></script>

Node.js

npm install flexsearch

In your code include as follows:

var FlexSearch = require("flexsearch");

Or pass in options when requiring:

var index = require("flexsearch").create({/* options */});

AMD

var FlexSearch = require("./flexsearch.js");

API Overview

Global methods:

• FlexSearch.create(<options>)
• FlexSearch.registerMatcher({KEY: VALUE})
• FlexSearch.registerEncoder(name, encoder)
• FlexSearch.registerLanguage(lang, {stemmer:{}, filter:[]})
• FlexSearch.encode(name, string)

Index methods:

• Index.add(id, string)
• Index.search(string, <limit>, <callback>)
• Index.search(<options>)
• Index.update(id, string)
• Index.remove(id)
• Index.reset()
• Index.destroy()
• Index.init(<options>)
• Index.info()
• Index.addMatcher({KEY: VALUE})
• Index.encode(string)

Usage

Create a new index

FlexSearch.create(<options>)

var index = new FlexSearch();

alternatively you can also use:

var index = FlexSearch.create();

Create a new index and choosing one of the built-in profiles

var index = new FlexSearch("speed");

Create a new index with custom options

var index = new FlexSearch({

    // default values:

    profile: "balance",
    encode: "icase",
    mode: "ngram",
    async: false,
    cache: false
});

Read more about custom options

Add items to an index

Index.add_(id, string)

index.add(10025, "John Doe");

Search items

Index.search(string|options, <limit>, <callback>)

index.search("John");

Limit the result:

index.search("John", 10);

Perform queries asynchronously:

index.search("John", function(result){
    
    // array of results
});

Pass custom options for each query:

index.search({
    
    query: "John",
    limit: 1000,
    threshold: 5, // >= initial threshold
    depth: 3,     // <= initial depth
    callback: function(results){/* ... */}
});

The same from above could also be written as:

index.search("John", {

    limit: 1000,
    threshold: 5,
    depth: 3
    
}, function(results){
    
    // ....
});

Get also suggestions for a query:

index.search({
    
    query: "John Doe",
    suggest: true
});

When suggestion is enabled all results will be filled up (until limit, default 1000) with similar matches ordered by relevance.

Update item to the index

Index.update(id, string)

index.update(10025, "Road Runner");

Remove item to the index

Index.remove(id)

index.remove(10025);

Reset index

index.reset();

Destroy the index

index.destroy();

Re-Initialize index

Index.init(<options>)

Note: Re-initialization will also destroy the old index!

Initialize (with same options):

index.init();

Initialize with new options:

index.init({

    /* options */
});

Add custom matcher

FlexSearch.registerMatcher({REGEX: REPLACE})

Add global matchers for all instances:

FlexSearch.registerMatcher({

    'ä': 'a', // replaces all 'ä' to 'a'
    'ó': 'o',
    '[ûúù]': 'u' // replaces multiple
});

Add private matchers for a specific instance:

index.addMatcher({

    'ä': 'a', // replaces all 'ä' to 'a'
    'ó': 'o',
    '[ûúù]': 'u' // replaces multiple
});

Add custom encoder

Define a private custom encoder during creation/initialization:

var index = new FlexSearch({

    encode: function(str){
    
        // do something with str ...
        
        return str;
    }
});

Register a global encoder to be used by all instances

FlexSearch.registerEncoder(name, encoder)

FlexSearch.registerEncoder('whitespace', function(str){

    return str.replace(/ /g, '');
});

Use global encoders:

var index = new FlexSearch({ encode: 'whitespace' });

Call encoders directly

Private encoder:

var encoded = index.encode("sample text");

Global encoder:

var encoded = FlexSearch.encode("whitespace", "sample text");

Mixup/Extend multiple encoders

FlexSearch.registerEncoder('mixed', function(str){
  
    str = this.encode("icase", str);  // built-in
    str = this.encode("whitespace", str); // custom
    
    return str;
});

FlexSearch.registerEncoder('extended', function(str){
  
    str = this.encode("custom", str);
    
    // do something additional with str ...

    return str;
});

Add custom tokenizer

Define a private custom tokenizer during creation/initialization:

var index = new FlexSearch({

    mode: function(str){
    
        // split string into components, e.g.:
        
        return str.split(/ -\//g);
    }
});

Add language-specific stemmer and/or filter

Stemmer: several linguistic mutations of the same word (e.g. "run" and "running")

Filter: a blacklist of words to be filtered out from indexing at all (e.g. "and", "to" or "be")

Define a private custom stemmer or filter during creation/initialization:

var index = new FlexSearch({

    stemmer: {
        
        // object {key: replacement}
        "ational": "ate",
        "tional": "tion",
        "enci": "ence",
        "ing": ""
    },
    filter: [ 
        
        // array blacklist
        "in",
        "into",
        "is",
        "isn't",
        "it",
        "it's"
    ]
});

Or assign stemmer/filters globally to a language:

FlexSearch.registerLanguage('us', {

    stemmer: {/* ... */},
    filter: [/* ... */]
});

Or use built-in stemmer or filter of your preferred languages:

<html>
<head>
    <script src="js/flexsearch.min.js"></script>
    <script src="js/lang/en.min.js"></script>
    <script src="js/lang/de.min.js"></script>
</head>
...

Now you can assign built-in stemmer during creation/initialization:

var index_en = new FlexSearch({stemmer: 'en', filter: 'en'});
var index_de = new FlexSearch({stemmer: 'de', filter: [/* custom */]});

In Node.js you just need require the language pack files to make them available:

require('lang/en.js');
require('lang/de.js');

It is also possible to compile language packs into the build as follows:

node compile SUPPORT_LANG_EN=true SUPPORT_LANG_DE=true

Get info about an index

index.info();

Returns information e.g.:

{
    "bytes": 64000,
    "id": 0,
    "matchers": 0,
    "size": 10000,
    "status": false
}

Chaining

Simply chain methods like:

var index = FlexSearch.create()
                      .addMatcher({'â': 'a'})
                      .add(0, 'foo')
                      .add(1, 'bar');

index.remove(0).update(1, 'foo').add(2, 'foobar');

Enable Contextual Index

Create index and just set the limit of relevance ("depth"):

var index = new FlexSearch({

    encode: "icase",
    mode: "strict",
    depth: 3
});

Enable Auto-Balanced Cache

Create index and just set a limit of cache entries:

var index = new FlexSearch({

    profile: "score",
    cache: 10000
});

Use WebWorker Sharding (Browser only)

Create index and just set the count of parallel threads:

var index = new FlexSearch({

    encode: "icase",
    mode: "full",
    async: true,
    worker: 4
});

Adding items to worker index as usual (async enabled):

index.add(10025, "John Doe");

Perform search and simply pass in callback like:

index.search("John Doe", function(results){

    // do something with array of results
});

Options

FlexSearch ist highly customizable. Make use of the the right options can really improve your results as well as memory economy or query time.

Option	Values	Description
profile	"memory" "speed" "match" "score" "balance" "fastest"	The configuration profile. Choose your preferation.
mode	"strict" "foward" "reverse" "ngram" "full" function()	The indexing mode (tokenizer). Choose one of the built-ins or pass a custom tokenizer function.
encode	false "icase" "simple" "advanced" "extra" "balance" function()	The encoding type. Choose one of the built-ins or pass a custom encoding function.
cache	false true {number}	Enable/Disable and/or set capacity of cached entries. When passing a number as a limit the cache automatically balance stored entries related to their popularity. Note: When just using "true" the cache has no limits and is actually 2-3 times faster (because the balancer do not have to run).
async	true false	Enable/Disable asynchronous processing. Each job will be queued for non-blocking processing. Recommended when using WebWorkers.
worker	false {number}	Enable/Disable and set count of running worker threads.
depth	false {number:0-9}	Enable/Disable contextual indexing and also sets contextual distance of relevance.
threshold	false {number:0-9}	Enable/Disable the threshold of minimum relevance all results should have. Note: It is also possible to set a lower threshold for indexing and pass a higher value when calling index.search(options).
stemmer	false {string} {function}	Disable or pass in language shorthand flag (ISO-3166) or a custom object.
filter	false {string} {function}	Disable or pass in language shorthand flag (ISO-3166) or a custom array.

Tokenizer

Tokenizer effects the required memory also as query time and flexibility of partial matches. Try to choose the most upper of these tokenizer which fits your needs:

Option	Description	Example	Memory Factor (n = length of word)
"strict"	index whole words	foobar	* 1
"ngram" (default)	index words partially through phonetic n-grams	foobar foobar	* n / 3
"foward"	incrementally index words in forward direction	foobar foobar	* n
"reverse"	incrementally index words in both directions	foobar foobar	* 2n - 1
"full"	index every possible combination	foobar foobar	* n * (n - 1)

Phonetic Encoding

Encoding effects the required memory also as query time and phonetic matches. Try to choose the most upper of these encoders which fits your needs, or pass in a custom encoder:

Option	Description	False-Positives	Compression
false	Turn off encoding	no	no
"icase" (default)	Case in-sensitive encoding	no	no
"simple"	Phonetic normalizations	no	~ 7%
"advanced"	Phonetic normalizations + Literal transformations	no	~ 35%
"extra"	Phonetic normalizations + Soundex transformations	yes	~ 60%
function()	Pass custom encoding: function(string):string

Comparison (Matching)

Reference String: "Björn-Phillipp Mayer"

Query	iCase	Simple	Advanced	Extra
björn	yes	yes	yes	yes
björ	yes	yes	yes	yes
bjorn	no	yes	yes	yes
bjoern	no	no	yes	yes
philipp	no	no	yes	yes
filip	no	no	yes	yes
björnphillip	no	yes	yes	yes
meier	no	no	yes	yes
björn meier	no	no	yes	yes
meier fhilip	no	no	yes	yes
byorn mair	no	no	no	yes
(false positives)	no	no	no	yes

Memory Usage

The required memory for the index depends on several options:

Encoding	Memory usage of every ~ 100,000 indexed word
false	260 kb
"icase" (default)	210 kb
"simple"	190 kb
"advanced"	150 kb
"extra"	90 kb
Mode	Multiplied with: (n = average length of indexed words)
"strict"	* 1
"ngram" (default)	* n / 3
"forward"	* n
"reverse"	* 2n - 1
"full"	* n * (n - 1)
Contextual Index	Multiply the sum above with:
	* (depth * 2 + 1)

Compare Memory Consumption

The book "Gulliver's Travels" (Swift Jonathan 1726) was used for this test.

Built-in Profiles

You can pass a built-in profile during creation/initialization. They have these following settings:

Standard profile: "default"

{
    encode: "icase",
    mode: "forward"
}

Memory-optimized profile: "memory"

{
    encode: "extra",
    mode: "strict",
    threshold: 7
}

Speed-optimized profile: "speed"

{
    encode: "icase",
    mode: "strict",
    threshold: 7,
    depth: 2
}

Matching-tolerant profile: "match"

{
    encode: "extra",
    mode: "full"
}

Relevance-optimized profile: "score"

{
    encode: "extra",
    mode: "strict",
    threshold: 5,
    depth: 5
}

Most-balanced profile: "balanced"

{
    encode: "balanced",
    mode: "ngram",
    threshold: 6,
    depth: 3
}

Absolute fastest profile: "fastest"

{
    encode: "icase",
    threshold: 9,
    depth: 1
}

Compare these options above:

• Benchmarks
• Relevance Scoring

Custom Builds

Full Build:

npm run build

Light Build:

npm run build-light

Build Language Packs:

npm run build-lang

Custom Build:

npm run build-custom SUPPORT_WORKER=true SUPPORT_ASYNC=true

Supported flags:

• SUPPORT_DEBUG
• SUPPORT_WORKER
• SUPPORT_CACHE
• SUPPORT_ASYNC
• SUPPORT_BUILTINS (built-in encoders)

Supported language flags (includes stemmer and filter):

• SUPPORT_LANG_EN
• SUPPORT_LANG_DE

Alternatively you can also use:

node compile SUPPORT_WORKER=true

The custom build was saved to flexsearch.custom.js

---

Copyright 2018 Thomas Wilkerling
Released under the Apache 2.0 License