nlevel

node.js odm for leveldb

npm install nlevel
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nlevel

nlevel - node.js odm for leveldb. It is built on top of levelup. The main ideas are to split db on sections (like collections in mongodb) and provide additional operations for this sections including manipulation with sets of objects.

Installation

npm install nlevel

Usage


var nlevel = require('nlevel');

// create db
var ldb = nlevel.db('./mydb', {valueEncoding: 'json'});

// store all sections in one object for convenience
var db = {};

// create value section which associate name with arbitrary value
db.cities = new nlevel.ValSection(ldb, 'cities');

db.cities.put(['Elina', 'Dillon', 'Saundra', 'Harmony'], function(err) {
    db.cities.get(function(err, cities) {
        if (err) throw err;
        // prints our array: [ 'Elina', 'Dillon', 'Saundra', 'Harmony' ]
        console.log(cities);
    });
});


// create documents section with projections (key order matters)
db.tasks = new nlevel.DocsSection(ldb, 'tasks', {
    projections: [
        // projection 1
        {key: {project: 1, version: 1, assignee: 1, id: 1}},
        // projection 2
        {key: {assignee: 1, project: 1, version: 1, id: 1}}
    ]
});

// put all tasks in a batch
db.tasks.put([{
    id: 1, project: 'proj 1', version: '1.0.0', assignee: 'bob', done: true
}, {
    id: 2, project: 'proj 1', version: '1.0.0', assignee: 'jane', done: false
}, {
    id: 3, project: 'proj 2', version: '2.0', assignee: 'bob', done: true
}, {
    id: 4, project: 'proj 2', version: '2.0', assignee: 'jane', done: true
}, {
    id: 5, project: 'proj 3', version: '0.1', assignee: 'sam', done: true
}, {
    id: 6, project: 'proj 3', version: '0.2', assignee: 'sam', done: false
}], function(err) {
    if (err) throw err;

    // NOTICE: in all calls key order matters

    // find task for selected assignee and project (it uses projection 2)
    db.tasks.find({
        start: {assignee: 'jane', project: 'proj 2'}
    }, function(err, tasks) {
        if (err) throw err;
        // prints [ 4 ]
        console.log(tasks.map(function(task) {return task.id;}));
    });

    // find tasks in specific project and version (it uses projection 1)
    db.tasks.find({
        start: {project: 'proj 1', version: '1.0.0'}
    }, function(err, tasks) {
        if (err) throw err;
        // prints [ 1, 2 ]
        console.log(tasks.map(function(task) {return task.id;}));
    });

    // get by full key (it uses projection 1)
    db.tasks.get({
        project: 'proj 1',
        version: '1.0.0',
        assignee: 'bob',
        id: 1
    }, function(err, task) {
        if (err) throw err;
        // prints 1
        console.log(task.id);
    });
});

Sections api

ValSection()

Value section constructor accepts db, name and returns instance of section

ValSection.put(value:Any, [callback(err)]:Function)

Put value to section accepts

ValSection.get(callback(err,value):Function)

Get value from section

ValSection.del([callback(err)]:Function)

Delete value from section

DocsSection()

Documents section stores objects in different projections. Constructor accepts db, name of section and options, options.projections is a list of target projections in which documents will be stored. Each projection defines key by which document will be accessible and value which is the presentation of document for projection. key is an object of field names and values for them. If value of key field is a function object will be passed to it and it should return string key otherwise value for this key from object will be get. If value is a function it will accept object and should return new object which will be stored for this projection. Any document should have an unique identifier - id field. Projection keys stores in alphabetical order and you can easily find documents (their presentations) between [start..end] (see find method api). Each document will have one key for each projection because of that you usually should put id field as last for projection. Field order at key object (and at find) matters.

DocsSection.put(docs:Object|Object[], [callback(err)]:Function)

Put one or array of documents to the section

DocsSection.find(params:Object, [callback(err,docs)]:Function)

Find documents

  • params.by - id of projection to use, by default it detects projection using condition (start, end)
  • params.start - start key
  • params.end - end key, by default it equals to params.start (with added boundary symbol)
  • params.reverse - a boolean, set to true if you want to go in reverse order
  • params.filter - function(value) if it returns falsy value document will be excluded from result
  • params.offset - integer, skip selected documents count
  • params.limit - limit count of documents in result
  • params.usingValues - (false by default) optimization flag, which can be set to force of using values for some operations which uses keys by default (e.g. counting)

DocsSection.count(findParams:Object, [callback(err,documentsCount)]:Function)

Count documents using findParams (see find). Notice: It counts keys (or values) internally (can take long time e.g. on large dataset)

DocsSection.get(key:Object, [projectionId]:String, [callback(err,doc)]:Function)

Get document by full key

DocsSection.update(key:Object, modifier:Object|Function, [callback(err)]:Function)

Update document by key using modifier which could object of fields and values to be updated or function which accepts document and returns modified document

DocsSection.multiUpdate(findParams:Object, modifier:Object|Function, [callback(err,updatedCount)]:Function)

Find documents using findParams (see find) and update them using modifier (see modifier description at update). Count of updated documents will be passed to callback (it could be zero). document

DocsSection.del(ids:String[]|Object[], [callback(err)]:Function)

Delete documents by array of their ids or array of objects with id field

Run tests

into cloned repository run

npm test
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