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nStore is a simple, in-process key/value database for node.js

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README.markdown

nStore

A simple in-process key/value document store for node.js. nStore uses a safe append-only data format for quick inserts, updates, and deletes. Also a index of all documents and their exact location on the disk is stored in in memory for fast reads of any document. This append-only file format means that you can do online backups of the datastore using simple tools like rsync. The file is always in a consistent state.

Warning

This library is still under development. There are bugs. APIs will change. Docs may be wrong.

Keep in mind this is something I make in my free time and that's something I've had very little of lately thanks to my many other projects. I would love for someone with database and javascript smarts to partner with to make nStore super awesome.

Setup

All the examples assume this basic setup. Loading the database is async so there is a callback for when it's safe to query the database.

Creating a database is easy, you just call the nStore function to generate a collection object.

// Load the library
var nStore = require('nstore');
// Create a store
var users = nStore.new('data/users.db', function () {
  // It's loaded now
});

Creating a document

To insert/update documents, just call the save function on the collection.

// Insert a new document with key "creationix"
users.save("creationix", {name: "Tim Caswell", age: 29}, function (err) {
    if (err) { throw err; }
    // The save is finished and written to disk safely
});

// Or insert with auto key
users.save(null, {name: "Bob"}, function (err, key) {
    if (err) { throw err; }
    // You now have the generated key
});

Loading a document

Assuming the previous code was run, a file will now exist with the persistent data inside it.

// Load the document with the key "creationix"
users.get("creationix", function (err, doc, key) {
    if (err) { throw err; }
    // You now have the document
});

Removing a document

Remove is by key only.

// Remove our new document
users.remove("creationix", function (err) {
    if (err) { throw err; }
    // The document at key "creationix" was removed
});

Clearing the whole collection

You can also quickly clear the entire collection

// Clear
users.clear(function (err) {
  // The database is now empty
});

This clears all the keys and triggers a compaction. Only after the compact finishes is the data truly deleted from the disk, however any further queries cannot see the old data anymore.

Querying the database

There are no indexes, however, nStore provides a simple query interface to get at data quickly and easily. You can filter using condition expressions or plain functions.

To use queries, you need to include the query addon.

var nStore = require('nstore');
nStore = nStore.extend(require('nstore/query')());

Query as a single callback

For convenience you can pass in a callback and get the results as a single object.

// Using a callback for buffered results
users.find({age: 29}, function (err, results) {
  // results is an object keyed by document key with the document as the value
});

Query using streams.

Also you can stream results.

var stream = users.find({age: 29});
stream.on("document", function (doc, key) {
  // This is a single document
});
stream.on("end", function () {
  // No more data is expected
})

all shortcut

If you want no condition you can use the all() shortcut.

users.all(function (err, results) {
  // All the users are now in a single object.
});

Structure of condition expressions.

A simple condition is pairs of key's and values. This builds a condition where all columns named by the key must equal the corresponding value.

This matches rows where name is "Tim" and age is 29:

{name: "Tim", age: 29}

If a key contains space, then the operator after it is used instead of equal.

This matches rows where age is greater than 18 and age is less than 50:

{"age >": 18, "age <": 50}

The supported operators are:

  • < - less than
  • <= - less than or equal to
  • >= - greater than or equal to
  • > - greater than
  • != or <> - not equal to

If an array of hash-objects is passed in, then each array item is grouped and ORed together.

This matches name is "Tim" or age < 8:

[{name: "Tim"}, {"age <": 8}]

Special compaction filter

There are times that you want to prune stale data from a database, like when using nStore to store session data. The problem with looping over the index keys and calling remove() on them is that it bloats the file. Deletes are actually appends to the file. Instead nStore exposes a special filter function that, if specified, will filter the data when compacting the data file.

// Prune any items that have a doc.lastAccess older than 1 hour.
var session = nStore.new('data/sessions.db', function () {
  // It's loaded now
});
session.filterFn = function (doc, meta) {
  return doc.lastAccess > Date.now() - 360000;
};
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