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https://github.com/eugeneware/levels

levels is a light-weight LevelDB full text search for node.js
https://github.com/eugeneware/levels

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levels is a light-weight LevelDB full text search for node.js

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README 

        
# levels



  levels is a light-weight LevelDB full text search for node.js. This is a port of the redis search [reds](https://github.com/visionmedia/reds) by [TJ Holowaychuk](https://github.com/visionmedia) to use LevelDb.



## Installation



      $ npm install levels



## Example



The first thing you'll want to do is create a `Search` instance, which allows you to pass a `key`, used for namespacing within Redis so that you may have several searches in the same db.



    var search = levels.createSearch('pets');



 levels acts against arbitrary numeric or string based ids, so you could utilize this library with essentially anything you wish, even combining data stores. The following example just uses an array for our "database", containing some strings, which we add to levels by calling `Search#index()` padding the body of text and an id of some kind, in this case the index.



```js

var strs = [];

strs.push('Tobi wants four dollars');

strs.push('Tobi only wants $4');

strs.push('Loki is really fat');

strs.push('Loki, Jane, and Tobi are ferrets');

strs.push('Manny is a cat');

strs.push('Luna is a cat');

strs.push('Mustachio is a cat');



strs.forEach(function(str, i){ search.index(str, i); });

```



 To perform a query against levels simply invoke `Search#query()` with a string, and pass a callback, which receives an array of ids when present, or an empty array otherwise.



```js

search

  .query(query = 'Tobi dollars')

  .end(function(err, ids){

    if (err) throw err;

    console.log('Search results for "%s":', query);

    ids.forEach(function(id){

      console.log('  - %s', strs[id]);

    });

    process.exit();

  });

  ```



 By default levels performs an intersection of the search words, the previous example would yield the following output:



```

Search results for "Tobi dollars":

  - Tobi wants four dollars

```



 We can tweak levels to perform a union by passing either "union" or "or" to `levels.search()` after the callback, indicating that _any_ of the constants computed may be present for the id to match.



```js

search

  .query(query = 'tobi dollars')

  .end(function(err, ids){

    if (err) throw err;

    console.log('Search results for "%s":', query);

    ids.forEach(function(id){

      console.log('  - %s', strs[id]);

    });

    process.exit();

  }, 'or');

```



 The intersection would yield the following since only one string contains both "Tobi" _and_ "dollars".



```

Search results for "tobi dollars":

  - Tobi wants four dollars

  - Tobi only wants $4

  - Loki, Jane, and Tobi are ferrets

```



## API



```js

levels.createSearch(key)

Search#index(text, id[, fn])

Search#remove(id[, fn]);

Search#query(text, fn[, type]);

```



 Examples:



```js

var search = levels.createSearch('misc');

search.index('Foo bar baz', 'abc');

search.index('Foo bar', 'bcd');

search.remove('bcd');

search.query('foo bar').end(function(err, ids){});

```



## About



  Currently levels strips stop words and applies the metaphone and porter stemmer algorithms to the remaining words before mapping the constants in Redis sets. For example the following text:



    Tobi is a ferret and he only wants four dollars



  Converts to the following constant map:



```js

{

  Tobi: 'TB',

  ferret: 'FRT',

  wants: 'WNTS',

  four: 'FR',

  dollars: 'DLRS'

}

```



 This also means that phonetically similar words will match, for example "stefen", "stephen", "steven" and "stefan" all resolve to the constant "STFN". levels takes this further and applies the porter stemming algorithm to "stem" words, for example "counts", and "counting" become "count".



 Consider we have the following bodies of text:



    Tobi really wants four dollars

    For some reason tobi is always wanting four dollars



 The following search query will then match _both_ of these bodies, and "wanting", and "wants" both reduce to "want".



    tobi wants four dollars



## Benchmarks



 Nothing scientific but preliminary benchmarks show that a small 1.6kb body of text is currently indexed in ~__6ms__, or __163__ ops/s. Medium bodies such as 40kb operate around __6__ ops/s, or __166ms__.



 Querying with a multi-word phrase, and an index containing ~3500 words operates around __5300__ ops/s. Not too bad.



 If working with massive documents, you may want to consider adding a "keywords" field, and simply indexing its value instead of multi-megabyte documents.



## License



(The MIT License)



Copyright (c) 2013 Eguene Ware <[email protected]>



Permission is hereby granted, free of charge, to any person obtaining

a copy of this software and associated documentation files (the

'Software'), to deal in the Software without restriction, including

without limitation the rights to use, copy, modify, merge, publish,

distribute, sublicense, and/or sell copies of the Software, and to

permit persons to whom the Software is furnished to do so, subject to

the following conditions:



The above copyright notice and this permission notice shall be

included in all copies or substantial portions of the Software.



THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,

EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY

CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,

TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE

SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.