mingo

MongoDB query language for in-memory objects

Install

$ npm install mingo

Features

• Supports Dot Notation for both <array>.<index> and <document>.<field> selectors
• Query and Projection Operators
  • Array Operators
  • Comparisons Operators
  • Element Operators
  • Evaluation Operators
  • Logical Operators
  • Projection Operators
• Aggregation Framework Operators
  • Pipeline Operators
  • Accumulator Operators
  • Expression Operators
    • Arithmetic Operators
    • Array Operators
    • Boolean Operators
    • Comparisons Operators
    • Conditional Operators
    • Date Operators
    • Literal Operators
    • Object Operators
    • Set Operators
    • Type Operators
    • String Operators
    • Variable Operators
• Support for adding custom operators using mingo.addOperators
• Match against user-defined types
• Support for aggregaion variables
  • $ROOT,$CURRENT,$DESCEND,$PRUNE,$KEEP,$REMOVE
• ES6 module compatible
• Support integrating with custom collections via mixin
• Query filtering and aggregation streaming.

For documentation on using query operators see mongodb

Documentation

• Package docs
• Custom Operators

Usage

// Use as es6 module
import mingo from 'mingo'

// or vanilla nodeJS
const mingo = require('mingo')

Changes in 3.0.0

Default exports and operators

The default export of the main module only includes Aggregator, Query, aggregate(), find(), and remove().

Only Query and Projection operators are loaded by default when using the main module. This is done using the side-effect module mingo/init/basic, and also automatically includes pipeline operators $project, $skip, $limit, and $sort.

If your application uses most of the available operators or you do not care about bundle size, you can load all operators as shown below.

// Note that doing this effectively imports the entire library into your bundle and unused operators cannot be tree shaked
import 'mingo/init/system'

Or from the node CLI

node -r 'mingo/init/system' myscript.js

Custom Operators

The addOperators function for registering custom operators and helper constants have been moved to mingo/core. The constants OP_XXX have been deprecated and replace with an enum type OperatorType also in mingo/core. The values defined include;

• ACCUMULATOR
• EXPRESSION
• PIPELINE
• PROJECTION
• QUERY

Lastly, the function argument to addOperators(operatorType, fn) now accepts an object with the these two internal functions;

• computeValue(obj: object | any[], expr: any, operator: string, options?: ComputeOptions): any
• resolve(obj: object | any[], selector: string, options?: ResolveOptions): any

Any extra utility may be imported directly from the specific module.

Importing submodules

Submodule imports are supported for both ES6 and ES5.

The following two examples are equivalent.

ES6

This work natively in typescript since it knows how to load commonJS modules as ES6. You may optionally install the esm module to use this syntax.

import { $unwind } from 'mingo/operators/pipeline'

ES5

Unlike the ES6 version, it is necessary to specify the operator module in the path to avoid loading any extras

const $unwind = require('mingo/operators/pipeline/unwind').$unwind

Configuration

To support tree-shaking, you may import and register specific operators that will be used in your application.

import { useOperators, OperatorType } from 'mingo/core'
import { $trunc } from 'mingo/operators/expression'
import { $bucket } from 'mingo/operators/pipeline'

useOperators(OperatorType.EXPRESSION, { $trunc, $floor })
useOperators(OperatorType.PIPELINE, { $bucket })

Using query object to test objects

import mingo from 'mingo'

// create a query with criteria
// find all grades for homework with score >= 50
let query = new mingo.Query({
  type: "homework",
  score: { $gte: 50 }
});

// test if an object matches query
query.test(doc)

Searching and Filtering

import mingo from 'mingo'

// input is either an Array or any iterable source (i.e Object{next:Function}) including ES6 generators.
let criteria = { score: { $gt: 10 } }

let query = new mingo.Query(criteria)

// filter collection with find()
let cursor = query.find(collection)

// alternatively use shorthand
// cursor = mingo.find(collection, criteria)

// sort, skip and limit by chaining
cursor.sort({student_id: 1, score: -1})
  .skip(100)
  .limit(100)

// count matches. exhausts cursor
cursor.count()

// classic cursor iterator (old school)
while (cursor.hasNext()) {
  console.log(cursor.next())
}

// ES6 iterators (new cool)
for (let value of cursor) {
  console.log(value)
}

// all() to retrieve matched objects. exhausts cursor
cursor.all()

Aggregation Pipeline

import { Aggregator } from 'mingo/aggregator'
import { useOperators, OperatorType } from 'mingo/core'
import { $match, $group } from 'mingo/operators/pipeline'
import { $min } from 'mingo/operators/accumulator'

// ensure the required operators are preloaded prior to using them.
useOperators(OperatorType.PIPELINE, { $match, $group })
useOperators(OperatorType.ACCUMULATOR, { $min })

let agg = new Aggregator([
  {'$match': { "type": "homework"}},
  {'$group': {'_id':'$student_id', 'score':{$min:'$score'}}},
  {'$sort': {'_id': 1, 'score': 1}}
])

// return an iterator for streaming results
let stream = agg.stream(collection)

// return all results. same as `stream.all()`
let result = agg.run(collection)

Benefits

• Better alternative to writing custom code for transforming collection of objects
• Quick validation of MongoDB queries without the need for a database
• MongoDB query language is among the best in the market and is well documented

Contributing

• Squash changes into one commit
• Run npm test to build and execute unit tests
• Submit pull request

License

MIT