abstract-nosql
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An abstract prototype for nosql database with sync and streamable (LevelDOWN API)
Abstract-nosql package is modified from abstract-leveldown to enhance the synchronous methods supports for development a node nosql database quickly and using easily. And streamable ability is added to abstract-nosql.
abstract-nosql Interface is neutral. There is no bias neither synchronous bias nor asynchronous bias. So that more people choose according to their own manner. For myself, I am not very concerned about the performance of javascript, I am more concerned about the efficiency of its development, as well as through functional programming (functions, closures such a simple concept) extend out of the rich and wonderful world. I still can not help but to think about performance issues. Asynchronous itself produces a small gap, because javascript reason this gap is magnified.
just saying that the asynchronous and synchronous consideration, if a function is only 1% of the opportunity to visit the IO, most of the time (99%) are in memory access. I want to different considerations, have different choices. And this decision is unlikely that done by the interface instead.
Synchronous operation converts into asynchronous operation is easy, and almost no performance loss, in turn, may not. Conversion are many ways, setImmediate is not the best, but it is the simplest one. ES6 generator or node-fibers could be a better way. the coroutine/fiber is lighter and more efficient than thread.
The setImmediate package could be extended to use different implementation(setImmediate, nextTick, ES6 generator, node-fiber) in different environment. So the simulated asynchronous uses this way, if you do not implement the asynchronous methods.
An abstract prototype matching the LevelDOWN API. Useful for extending LevelUP functionality by providing a replacement to LevelDOWN.
As of version 0.7, LevelUP allows you to pass a 'db' option when you create a new instance. This will override the default LevelDOWN store with a LevelDOWN API compatible object.
Abstract LevelDOWN provides a simple, operational noop base prototype that's ready for extending. By default, all operations have sensible "noops" (operations that essentially do nothing). For example, simple operations such as .open(callback) and .close(callback) will simply invoke the callback (on a next tick). More complex operations perform sensible actions, for example: .get(key, callback) will always return a 'NotFound' Error on the callback.
You add functionality by implementing the underscore versions of the operations. For example, to implement a put() operation you add a _put() method to your object. Each of these underscore methods override the default noop operations and are always provided with consistent arguments, regardless of what is passed in by the client.
Additionally, all methods provide argument checking and sensible defaults for optional arguments. All bad-argument errors are compatible with LevelDOWN (they pass the LevelDOWN method arguments tests). For example, if you call .open() without a callback argument you'll get an Error('open() requires a callback argument'). Where optional arguments are involved, your underscore methods will receive sensible defaults. A .get(key, callback) will pass through to a ._get(key, options, callback) where the options argument is an empty object.
'open' and 'ready' event after the database is opened.'closed' event after the database is closed.see abstract-object
All Errors are derived from the AbstractError.
the error codes:
var OpenError = createError("CanNotOpen", NotOpened)
var CloseError = createError("CanNotClose", 52)
var AlreadyEndError = createError("AlreadyEnd", 53)
Once implements the AbstractIterator:
the db should be the streamable.
But, you should install the nosql-stream package first.
npm install nosql-stream
see nosql-stream for more details
create a readable stream.
the data item is key.
create a readable stream.
the data item is value.
create a readable stream.
the data item is an object: {key:key, value:value}.
arguments
'next': the raw key data to ensure the readStream return keys is greater than the key. See 'last' event.
'filter' (function): to filter data in the stream
'range' (string or array): the keys are in the give range as the following format:
'gt' (greater than), 'gte' (greater than or equal) define the lower bound of the range to be streamed. Only records where the key is greater than (or equal to) this option will be included in the range. When reverse=true the order will be reversed, but the records streamed will be the same.'lt' (less than), 'lte' (less than or equal) define the higher bound of the range to be streamed. Only key/value pairs where the key is less than (or equal to) this option will be included in the range. When reverse=true the order will be reversed, but the records streamed will be the same.'start', 'end' legacy ranges - instead use 'gte', 'lte''match' (string): use the minmatch to match the specified keys.
'limit' (number, default: -1): limit the number of results collected by this stream. This number represents a maximum number of results and may not be reached if you get to the end of the data first. A value of -1 means there is no limit. When reverse=true the highest keys will be returned instead of the lowest keys.'reverse' (boolean, default: false): a boolean, set true and the stream output will be reversed.'keys' (boolean, default: true): whether the 'data' event should contain keys. If set to true and 'values' set to false then 'data' events will simply be keys, rather than objects with a 'key' property. Used internally by the createKeyStream() method.'values' (boolean, default: true): whether the 'data' event should contain values. If set to true and 'keys' set to false then 'data' events will simply be values, rather than objects with a 'value' property. Used internally by the createValueStream() method.return
the standard 'data', 'error', 'end' and 'close' events are emitted.
the 'last' event will be emitted when the last data arrived, the argument is the last raw key.
if no more data the last key is undefined.
var MemDB = require("memdown-sync")
var db1 = MemDB("db1")
var db2 = MemDB("db2")
var ws = db1.writeStream()
var ws2 = db2.createWriteStream()
ws.on('error', function (err) {
console.log('Oh my!', err)
})
ws.on('finish', function () {
console.log('Write Stream finish')
//read all data through the ReadStream
db1.readStream().on('data', function (data) {
console.log(data.key, '=', data.value)
})
.on('error', function (err) {
console.log('Oh my!', err)
})
.on('close', function () {
console.log('Stream closed')
})
.on('end', function () {
console.log('Stream closed')
})
.pipe(ws2) //copy Database db1 to db2:
})
ws.write({ key: 'name', value: 'Yuri Irsenovich Kim' })
ws.write({ key: 'dob', value: '16 February 1941' })
ws.write({ key: 'spouse', value: 'Kim Young-sook' })
ws.write({ key: 'occupation', value: 'Clown' })
ws.end()
filter usage:
db.createReadStream({filter: function(key, value){
if (/^hit/.test(key))
return db.FILTER_INCLUDED
else key == 'endStream'
return db.FILTER_STOPPED
else
return db.FILTER_EXCLUDED
}})
.on('data', function (data) {
console.log(data.key, '=', data.value)
})
.on('error', function (err) {
console.log('Oh my!', err)
})
.on('close', function () {
console.log('Stream closed')
})
.on('end', function () {
console.log('Stream closed')
})
next and last usage for paged data demo:
var callbackStream = require('callback-stream')
var lastKey = null;
function nextPage(db, aLastKey, aPageSize, cb) {
var stream = db.readStream({next: aLastKey, limit: aPageSize})
stream.on('last', function(aLastKey){
lastKey = aLastKey;
});
stream.pipe(callbackStream(function(err, data){
cb(data, lastKey)
}))
}
var pageNo = 1;
dataCallback = function(data, lastKey) {
console.log("page:", pageNo);
console.log(data);
++pageNo;
if (lastKey) {
nextPage(db, lastKey, 10, dataCallback);
}
else
console.log("no more data");
}
nextPage(db, lastKey, 10, dataCallback);
Remember that each of these methods, if you implement them, will receive exactly the number and order of arguments described. Optional arguments will be converted to sensible defaults.
this is an optional method for performance.
this is an optional method for performance.
arguments
return
this is an optional method for performance.
this is an optional method for performance.
arguments
If batch() is called without argument or with only an options object then it should return a Batch object with chainable methods. Otherwise it will invoke a classic batch operation.
the batch should be rename to transact more accurate.
batch() can be used for very fast bulk-write operations (both put and delete). The array argument should contain a list of operations to be executed sequentially, although as a whole they are performed as an atomic operation inside LevelDB. Each operation is contained in an object having the following properties: type, key, value, where the type is either 'put' or 'del'. In the case of 'del' the 'value' property is ignored. Any entries with a 'key' of null or undefined will cause an error to be returned on the callback and any 'type': 'put' entry with a 'value' of null or undefined will return an error.
var ops = [
{ type: 'del', key: 'father' }
, { type: 'put', key: 'name', value: 'Yuri Irsenovich Kim' }
, { type: 'put', key: 'dob', value: '16 February 1941' }
, { type: 'put', key: 'spouse', value: 'Kim Young-sook' }
, { type: 'put', key: 'occupation', value: 'Clown' }
]
db.batch(ops, function (err) {
if (err) return console.log('Ooops!', err)
console.log('Great success dear leader!')
})
By default an batch() operation without argument returns a blank AbstractChainedBatch object. The prototype is available on the main exports for you to extend. If you want to implement chainable batch operations then you should extend the AbstractChaindBatch and return your object in the _chainedBatch() method.
You can override the IteratorClass to your Iterator.
After override this, it is not necessary to implement the "_iterator()" method.
By default an iterator() operation returns a blank AbstractIterator object. The prototype is available on the main exports for you to extend. If you want to implement iterator operations then you should extend the AbstractIterator and return your object in the _iterator(options) method.
AbstractIterator implements the basic state management found in LevelDOWN. It keeps track of when a next() is in progress and when an end() has been called so it doesn't allow concurrent next() calls, it does it allow end() while a next() is in progress and it doesn't allow either next() or end() after end() has been called.
arguments
'gt' (greater than), 'gte' (greater than or equal) define the lower bound of the range to be streamed. Only records where the key is greater than (or equal to) this option will be included in the range. When reverse=true the order will be reversed, but the records streamed will be the same.'lt' (less than), 'lte' (less than or equal) define the higher bound of the range to be streamed. Only key/value pairs where the key is less than (or equal to) this option will be included in the range. When reverse=true the order will be reversed, but the records streamed will be the same.'reverse' (boolean, default: false): a boolean, set true and the stream output will be reversed. Beware that due to the way LevelDB works, a reverse seek will be slower than a forward seek.'keys' (boolean, default: true): whether contain keys.'values' (boolean, default: true): whether contain values.'limit' (number, default: -1): limit the number of results collected by this stream. This number represents a maximum number of results and may not be reached if you get to the end of the data first. A value of -1 means there is no limit. When reverse=true the highest keys will be returned instead of the lowest keys.'fillCache' (boolean, default: false): wheather LevelDB's LRU-cache should be filled with data read.Provided with the current instance of AbstractNoSql by default.
A simplistic in-memory LevelDOWN replacement
use sync methods:
var util = require('util')
, AbstractNoSql = require('./').AbstractNoSql
// constructor, passes through the 'location' argument to the AbstractNoSql constructor
function FakeNoSqlDatabase (location) {
AbstractNoSql.call(this, location)
}
// our new prototype inherits from AbstractNoSql
util.inherits(FakeNoSqlDatabase, AbstractNoSql)
// implement some methods
FakeNoSqlDatabase.prototype._openSync = function (options) {
this._store = {}
return true
}
FakeNoSqlDatabase.prototype._putSync = function (key, value, options) {
key = '_' + key // safety, to avoid key='__proto__'-type skullduggery
this._store[key] = value
return true
}
//the isExists is an optional method:
FakeNoSqlDatabase.prototype._isExistsSync = function (key, options) {
return this._store.hasOwnProperty('_' + key)
}
FakeNoSqlDatabase.prototype._getSync = function (key, options) {
var value = this._store['_' + key]
if (value === undefined) {
// 'NotFound' error, consistent with LevelDOWN API
throw new Error('NotFound')
}
return value
}
FakeNoSqlDatabase.prototype._delSync = function (key, options) {
delete this._store['_' + key]
return true
}
//use it directly
var db = new FakeNoSqlDatabase()
//sync:
db.put('foo', 'bar')
var result = db.get('foo')
//async:
db.put('foo', 'bar', function (err) {
if (err) throw err
db.get('foo', function (err, value) {
if (err) throw err
console.log('Got foo =', value)
db.isExists('foo', function(err, isExists){
if (err) throw err
console.log('isExists foo =', isExists)
})
})
})
//stream:
db.readStream().on('data', function(data){
})
// Or use it in LevelUP
var levelup = require('levelup')
var db = levelup('/who/cares/', {
// the 'db' option replaces LevelDOWN
db: function (location) { return new FakeNoSqlDatabase(location) }
})
//async:
db.put('foo', 'bar', function (err) {
if (err) throw err
db.get('foo', function (err, value) {
if (err) throw err
console.log('Got foo =', value)
db.isExists('foo', function(err, isExists){
if (err) throw err
console.log('isExists foo =', isExists)
})
})
})
//sync:
db.put('foo', 'bar')
console.log(db.get('foo'))
console.log(db.isExists('foo'))
use async methods(no sync supports):
var util = require('util')
, AbstractNoSql = require('./').AbstractNoSql
// constructor, passes through the 'location' argument to the AbstractNoSql constructor
function FakeNoSqlDatabase (location) {
AbstractNoSql.call(this, location)
}
// our new prototype inherits from AbstractNoSql
util.inherits(FakeNoSqlDatabase, AbstractNoSql)
// implement some methods
FakeNoSqlDatabase.prototype._open = function (options, callback) {
// initialise a memory storage object
this._store = {}
// optional use of nextTick to be a nice async citizen
process.nextTick(function () { callback(null, this) }.bind(this))
}
FakeNoSqlDatabase.prototype._put = function (key, value, options, callback) {
key = '_' + key // safety, to avoid key='__proto__'-type skullduggery
this._store[key] = value
process.nextTick(callback)
}
//the isExists is an optional method:
FakeNoSqlDatabase.prototype._isExists = function (key, options, callback) {
var value = this._store.hasOwnProperty('_' + key)
process.nextTick(function () {
callback(null, value)
})
}
FakeNoSqlDatabase.prototype._get = function (key, options, callback) {
var value = this._store['_' + key]
if (value === undefined) {
// 'NotFound' error, consistent with LevelDOWN API
return process.nextTick(function () { callback(new Error('NotFound')) })
}
process.nextTick(function () {
callback(null, value)
})
}
FakeNoSqlDatabase.prototype._del = function (key, options, callback) {
delete this._store['_' + key]
process.nextTick(callback)
}
// now use it in LevelUP
var levelup = require('levelup')
var db = levelup('/who/cares/', {
// the 'db' option replaces LevelDOWN
db: function (location) { return new FakeNoSqlDatabase(location) }
})
db.put('foo', 'bar', function (err) {
if (err) throw err
db.get('foo', function (err, value) {
if (err) throw err
console.log('Got foo =', value)
})
})
See MemDOWN if you are looking for a complete in-memory replacement for LevelDOWN.
Abstract LevelDOWN is an OPEN Open Source Project. This means that:
Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.
See the CONTRIBUTING.md file for more details.
Abstract LevelDOWN is only possible due to the excellent work of the following contributors:
| Riceball LEE | GitHub/snowyu | |
|---|---|---|
| Rod Vagg | GitHub/rvagg | Twitter/@rvagg |
| John Chesley | GitHub/chesles | Twitter/@chesles |
| Jake Verbaten | GitHub/raynos | Twitter/@raynos2 |
| Dominic Tarr | GitHub/dominictarr | Twitter/@dominictarr |
| Max Ogden | GitHub/maxogden | Twitter/@maxogden |
| Lars-Magnus Skog | GitHub/ralphtheninja | Twitter/@ralphtheninja |
| David Björklund | GitHub/kesla | Twitter/@david_bjorklund |
| Julian Gruber | GitHub/juliangruber | Twitter/@juliangruber |
| Paolo Fragomeni | GitHub/hij1nx | Twitter/@hij1nx |
| Anton Whalley | GitHub/No9 | Twitter/@antonwhalley |
| Matteo Collina | GitHub/mcollina | Twitter/@matteocollina |
| Pedro Teixeira | GitHub/pgte | Twitter/@pgte |
| James Halliday | GitHub/substack | Twitter/@substack |
| Thomas Watson Steen | GitHub/watson | Twitter/@wa7son |
Copyright (c) 2012-2014 Abstract LevelDOWN contributors (listed above).
Abstract LevelDOWN is licensed under the MIT license. All rights not explicitly granted in the MIT license are reserved. See the included LICENSE.md file for more details.
FAQs
An abstract prototype for nosql database with sync and streamable (LevelDOWN API)
The npm package abstract-nosql receives a total of 4 weekly downloads. As such, abstract-nosql popularity was classified as not popular.
We found that abstract-nosql demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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