A sample of Tree Documents structure in Mongodb

tree_structure_mongodb.js

// Creating root category
db.categories.insert({'_id': 0, 'name': 'Computer Hardware' })

// Creating 1st level category
db.categories.insert({'_id': 1, 'name': 'Computer Components', 'parent_id': 0, 'ancestors': [0]})

// Creating 2nd level categories
db.categories.insert({'_id': 2, 'name': 'CPUs', 'parent_id': 1, 'ancestors': [1, 0]})
db.categories.insert({'_id': 3, 'name': 'Motherboards', 'parent_id': 1, 'ancestors': [1, 0]})
db.categories.insert({'_id': 4, 'name': 'Memory', 'parent_id': 1, 'ancestors': [1, 0]})
db.categories.insert({'_id': 5, 'name': 'Harddrives', 'parent_id': 1, 'ancestors': [1, 0]})
db.categories.insert({'_id': 6, 'name': 'Video Cards', 'parent_id': 1, 'ancestors': [1, 0]})
db.categories.insert({'_id': 7, 'name': 'Computer Cases', 'parent_id': 1, 'ancestors': [1, 0]})
db.categories.insert({'_id': 8, 'name': 'Power Supplies', 'parent_id': 1, 'ancestors': [1, 0]})
db.categories.insert({'_id': 9, 'name': 'Fans & PC Cooling', 'parent_id': 1, 'ancestors': [1, 0]})

// Creating 3rd level categories
db.categories.insert({'_id': 10, 'name': 'Processors - Desktops', 'parent_id': 2, 'ancestors': [2, 1, 0]})
db.categories.insert({'_id': 11, 'name': 'Processors - Servers', 'parent_id': 2, 'ancestors': [2, 1, 0]})

// Sample query to find all descendants of the CPUs Category
db.categories.find({'ancestors': 2})