AggregationBuilder

AggregationBuilder is a utility class that simplifies the creation of MongoDB aggregation pipelines by providing a fluent interface for building complex aggregation stages.

Installation

• You can install the AggregationBuilder package using npm:

npm install aggregation-builder

Stages

• Match - The $match stage filters documents based on specified conditions.

• Group - The $group stage groups documents by a specified _id expression and allows you to perform aggregations on grouped data.

• Sort - The $sort stage sorts documents in the pipeline based on specified criteria.

• Project - The $project stage reshapes documents, including including or excluding fields.

• Unwind - The $unwind stage deconstructs an array field from input documents, creating one document per array element.

• Lookup - The $lookup stage performs a left outer join with another collection, combining documents based on specified conditions.

• Sample - The $sample stage randomly selects a specified number of documents from the pipeline.

• Facet - The $facet stage allows you to run multiple pipelines within a single aggregation operation.

• Limit - The $limit stage restricts the number of documents in the pipeline.

• Count - The $count stage returns the count of documents in the pipeline.

• Skip - The $skip stage skips a specified number of documents from the pipeline.

• Filter - The $filter stage filters an array field in a document, returning only the elements that match the specified condition.

• Unset - The $unset stage removes specified fields from documents in the pipeline.

• AddFields - The $addFields stage adds new fields to documents in the pipeline.

Building the Pipeline

The aggregation pipeline is built using a fluent interface. Each stage is added to the pipeline using methods like .match(), .group(), .sort(), etc. You can chain these methods to construct a comprehensive aggregation pipeline. Finally, the .build() method returns the complete aggregation pipeline.

• For detailed information on MongoDB aggregation stages, consult the MongoDB Aggregation Pipeline documentation.

Usage/Examples

const { AggregationBuilder } = require('./AggregationBuilder');

// Create an instance of AggregationBuilder
const aggregationBuilder = new AggregationBuilder();

// Build the aggregation pipeline using various stages
const pipeline = aggregationBuilder
  .match({ age: { $gte: 18 } })
  .group({
    _id: '$department',
    averageSalary: { $avg: '$salary' }
  })
  .sort({ age: 1 })
  .project({ fullName: { $concat: ['$firstName', ' ', '$lastName'] } })
  .unwind('$skills')
  .lookup('departments', 'departmentId', '_id', 'departmentInfo')
  .lookupMatchWithTwoFields(
    'orders',
    ['customerId', 'productId'],
    ['_id', 'productId'],
    [],
    'orderDetails'
  )
  .sample(5)
  .facet({
    ageStats: [{ $group: { _id: null, avgAge: { $avg: '$age' } } }],
    departmentStats: [{ $group: { _id: '$department', count: { $sum: 1 } } }]
  })
  .limit(10)
  .count('totalEmployees')
  .skip(20)
  .filter({
    input: '$items',
    as: 'item',
    cond: { $gte: ['$$item.price', 100] }
  })
  .unset(['temporaryField', 'obsoleteField'])
  .addFields({ isNewEmployee: { $cond: { if: { $gte: ['$hireDate', new Date('2023-01-01')] }, then: true, else: false } } })
  .build();

// Execute the aggregation pipeline
db.collection.aggregate(pipeline);

Conclusion

The AggregationBuilder class simplifies the creation of complex MongoDB aggregation pipelines by providing a fluent and intuitive interface for building various aggregation stages.

Feel free to adjust the content of the `readme.md` file as needed. This provides a comprehensive guide to using each stage of the `AggregationBuilder` class along with relevant examples.

Package Information

• Package Name: mongodb-aggregation-helpers
• Author Name: gautamtheprogrammer
• GitHub URL: https://github.com/gautamlovecoding/mongodb-aggregation-helpers