LINQ-Inspired Document Querying

EntityTS brings the power and familiarity of LINQ to document databases via DocumentQuery and NoSqlSet<T>.

You can write TypeScript lambda expressions or fluent filter chains that compile directly into native MongoDB filter documents, DynamoDB KeyCondition/Filter expressions, and Redis scans.

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Fluent Filtering with .where()

You can query documents using type-safe lambdas, fluent condition builders, or partial objects:

1. Pure Lambda Predicates

EntityTS parses TypeScript lambda predicates into native query filters:

const activeAdults = await users
  .where(u => u.age >= 21 && u.role === 'admin')
  .orderByDescending(u => u.createdAt)
  .take(10)
  .toList();

Compiles to MongoDB filter:

{
  "age": { "$gte": 21 },
  "role": "admin"
}

2. Fluent WhereClause Builder

const results = await users
  .where(w => {
    w.where('age', '>=', 18);
    w.and('status', '=', 'active');
  })
  .toList();

3. Partial Document Matching

const admins = await users.where({ role: 'admin', isVerified: true }).toList();

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Projections, Sorting & Pagination

Control exactly which fields are retrieved and how documents are ordered:

const summaries = await users
  .where(u => u.age > 18)
  .project({ name: 1, email: 1, age: 1 })
  .orderBy(u => u.name, 'asc')
  .skip(20)
  .take(10)
  .toList();

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Terminal Operations

Method	Return Type	Description
.toList()	Promise<T[]>	Executes query and returns all matching documents
.firstOrDefault()	Promise<T | null>	Returns the first matching document or null
.singleOrDefault()	Promise<T | null>	Returns the single matching document, throwing if multiple match
.count()	Promise<number>	Returns the count of matching documents
.any()	Promise<boolean>	Returns true if at least one document matches

// Check existence
const exists = await users.where(u => u.email === 'alice@example.com').any();

// Count documents
const count = await users.where(u => u.age >= 18).count();

// Retrieve first match
const user = await users.where(u => u.id === 'usr_1').firstOrDefault();

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Aggregation Pipelines

For advanced analytics, NoSqlSet<T> supports chaining custom aggregation stages:

const stats = await users
  .where(u => u.isActive === true)
  .aggregate([
    {
      $group: {
        _id: '$department',
        averageAge: { $avg: '$age' },
        totalUsers: { $sum: 1 },
      },
    },
    {
      $sort: { totalUsers: -1 },
    },
  ]);