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 manipulations
with set of objects.

Installation

``
npm install nlevel
`

Usage

`js

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

$3

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

$3

Put value to section accepts

$3

Get value from section

$3

Delete value from section

$3

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.

$3

Put one or array of documents to the section

$3

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)

$3

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

$3

Get document by full key

$3

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

$3

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

$3

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

Run tests

into cloned repository run

`
npm test
``