MongoDB: Filter documents against array length | Sajad Torkamani

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Find by array length

Using $where (not efficient)

Using $exists (efficient)

Find by array length

// Find all records that have 2 employees
db.Firm.find({ employees: { "$size": 2 }})

Using `$where` (not efficient)

Not as efficient but useful when you’re querying using the Mongo shell:

Find all documents that have more than 5 employees
db.Firm.find({ $where: "this.employees.length > 5"})

Using `$exists` (efficient)

// Find all records that have at least 2 employees
db.Firm.find({ 'employees.1': { $exists: true } })

Tagged: MongoDB

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