Synopsis

Create and manage indices for your leveldb database.

Provides simple querying of indexed data
Supports inverted sorting of indices (e.g. sort a Date from newer to older)
Uses bytewise encoding for indices.
Supports automatic indexing (using hooks).
Works with changing fields (with some performance impact during reads).

Stability

2 - Unstable

The API is in the process of settling, but has not yet had sufficient real-world testing to be considered stable.

Usage

var indico = require('level-indico');

var db = sublevel(level('db', { valueEncoding: 'json' }));

//set indices on a sublevel
var posts = indico(db.sublevel('posts'));

/*
  post = {
    title: String,
    commentCount: Number,
    user: {
      name: String, 
      id: String
    },
    createdDate: Date
  }

*/

//set a single index,  and save the index object for later use
var titleIndex = posts.indico.ensureIndex(['title']);
posts.indico.ensureIndex(['createdDate']);
//works with nested properties
posts.indico.ensureIndex(['user.id']);
//set a compound index
posts.indico.ensureIndex(['title', 'commentCount']);
//set a descending index on 'createdDate' (so it sorts from newer to older)
posts.indico.ensureIndex([['createdDate', 'desc'], 'commentCount']);

//[...] Put some data

//Now query...

//SELECT * FROM posts WHERE title = 'Hello'
titleIndex.find({start: ['Hello'], end: ['Hello']}, function (err, data) {
  //...
});

//SELECT * FROM posts WHERE title = 'Hello' AND commentCount >= 1
posts.indico.findBy(['title', 'commentCount'], {start: ['Hello', 1], end: ['Hello', undefined]}, function (err, data) {
  //...
});

//SELECT * FROM posts ORDER BY createdDate DESC
posts.indico.findBy([['createdDate', 'desc']], {start: [null], end: [undefined]}, function (err, data) {
  //...
});

//SELECT * FROM posts WHERE createdDate <= '1/1/2010' AND commentCount >= 10
posts.indico.findBy([['createdDate', 'desc'], 'commentCount'], {
    start: [new Date(2010,01,00), 10],
    end: [undefined, undefined]
  }, function (err, data) {
  //...
});

//SELECT * FROM posts ORDER BY createdDate ASC
posts.indico.streamBy([['createdDate', 'desc']], {start: [null], end: [undefined]})
.on('data', function(data) {
//...
})
.on(close, function() {
//...
})

API

db.indico

indico.ensureIndex(properties)

Sets an index on the specified properties.

Arguments

properties: an Array listing the properties to index. Each item can be:
- String: (e.g 'title') the property to include in the index, by default sorted Ascending.
- Array: An array containing 2 String items:
  - [0]: The property name
  - [1]: The sorting order, one between 'desc' and 'asc'.

Returns

QueryManager for the specified index.

Example

var titleIndex = db.indico.ensureIndex(['title']);
var dateAndCommentIndex = db.indico.ensureIndex([['createdDate', 'desc'], 'commentCount']);

indico.index(properties)

Alias of indico.ensureIndex

indico.findBy(properties, options, callback)

Invokes find on the QueryManager corresponding to the specified properties

indico.streamBy(properties, options)

Invokes stream on the QueryManager corresponding to the specified properties

QueryManager

find(options, callback)

Finds all values corresponding to the specified options

Arguments

options:
- start: Array specifying the index you wish to start the read at. It must have the same arity of the index.
- end: Array specifying index you wish to end the read on. It must have the same arity of the index.
callback: function(err, data)

Note: Since level-indico uses bytewise under the hood, it means that null will sort before any other value, while undefined will sort aftern any other value.

Example

//SELECT * FROM posts WHERE title = 'Hello' ORDER BY commentCount ASC
posts.indico.findBy(['title', 'commentCount'], {start: ['Hello', null], end: ['Hello', undefined]}, function (err, data) {
  //...
});

stream(options)

Same as find, but returns a ReadableStream for the specified query.

TODO

Index nested objects (not just values)
Full reindex

Breaking changes

0.1 -> 0.2

ensureIndex('title', 'content') becomes ensureIndex(['title', 'content'])

License

MIT

gejiajun-hangzhou / level-indico Goto Github PK

level-indico's Introduction