Exercise 1 - Which Query that hit the indexes ?

index_excercise_1.js

// Let's say we have a store database where the database has products collection with several documents in it
use store
db.products.insert({'sku': '119-4567-7895', 'price':359.99, 'description': 'Intel Core i7-4770K Haswell Quad-Core 3.5GHz LGA 1150 84W Desktop Processor Intel HD Graphics BX80646I74770K', 'category':'CPU-Processors-Desktops', 'brand': 'Intel', 'reviews': [{'author': 'Mr.T', 'pros':"I play video game and I do video editiing. When it's time to compress movie and work on it, it's really fast.", 'cons': "The temperature is on the high side, but I think it's the way they run."}]})
db.products.insert({'sku': '121-6478-7234', 'price':374.99, 'description': 'ASUS GTX770-DC2OC-2GD5 GeForce GTX 770 2GB 256-Bit GDDR5 PCI Express 3.0 HDCP Ready SLI Support Video Card', 'category': 'Desktop Graphics Cards','brand': 'ASUS', 'reviews': [{'author': 'Slyder', 'pros':"Plug and play super fast works great so far nothing wrong with the way it's been working", 'cons':"Nothing yet"}]})
db.products.insert({'sku': '121-6478-7234', 'price':529.99, 'description': 'SAMSUNG 840 EVO MZ-7TE1T0BW 2.5" 1TB SATA III MLC Internal Solid State Drive (SSD)', 'category': 'Internal SSD','brand': 'Samsung', 'reviews': [{'author': 'Joana', 'pros':"Super fast drive for load times, no noise, less power use for laptops.", 'cons':" Expensive compared to standard hard drives."}]})

// Put index on sku field
db.products.ensureIndex({'sku':1})

// Put index on price field
db.products.ensureIndex({'price':1})

// Put index on description field
db.products.ensureIndex({'description':1})

// Put a compound index on both category & brand fields
db.products.ensureIndex({'category':1, 'brand':1})

// Put index on reviews.author 
db.products.ensureIndex({'reviews.author':1})

// If we find product by specific brand, does it utilise any index ?
db.products.find({'brand': 'ASUS'}).explain()

// What if we sort the prior query by price, ascending ?
db.products.find({'brand': 'ASUS'}).sort({'price':1}).explain()

// different criteria but still use sorting
db.products.find({$and: [{'price':{$gt:300.0}}, {'price': {$lt: 400.0}}]}).sort({'price':1}).explain()