A simple schema design set for modeling a product, category and cart for an eCommerce system using mongodb

1. Simple e-commerce schema
Christian Kvalheim @christkv

2. Agenda
• The product
• The categories
• Product by categories
• Category navigation
• The cart
• Add product to cart
• Remove product from cart
• Expire cart
• The checkout

3. The product
{
sku: "111445GB3",
title: "Simsong One mobile phone",
description: "The greatest Onedroid phone on the market .....",
manufacture_details: {
model_number: "A123X",
release_date: new ISODate("2012-05-17T08:14:15.656Z")
},
shipping_details: {
weight: 350,
width: 10,
height: 10,
depth: 1
},
quantity: 99,
pricing: {
price: 1000
}
}

4. The product, add categories
db.products.update(
{sku: "111445GB3"},
{$set: { categories: ['mobile/15G', 'mobile/fm'] }});
{
sku: "111445GB3",
title: "Simsong One mobile phone",
description: "The greatest Onedroid phone on the market .....",
manufacture_details: {
model_number: "A123X", release_date: new
ISODate("2012-05-17T08:14:15.656Z")
},
shipping_details: {
weight: 350, width: 10, height: 10, depth: 1
},
quantity: 99,
categories: ['mobile/15G', 'mobile/
fm'],

5. The product, add categories
• Add an index on the categories
db.products.ensureIndex({categories:1 })
• Locate all the products in a category
db.products.find({categories: /^mobile/fm/})
• If we use case sensitive pre-fix regular expressions
we use the btree index and have very fast lookups

6. Categories
{
title: "Mobiles containing a FM radio",
parent: "mobile",
path: "mobile/fm"
}
db.categories.insert({title: "Mobiles containing a FM radio", parent:
"mobile", path: "mobile/fm"})
db.categories.insert({title: "Mobiles with 15G support", parent:
"mobile", path: "mobile/15G"})
db.categories.ensureIndex({parent: 1, path: 1})
db.categories.ensureIndex({path: 1})

7. Categories, queries
• Locate all categories directly under /mobile
db.categories.find({parent: /^mobile/}, {_id: 0, path: 1})
• Locate all the categories under /mobile
db.categories.find({path: /^mobile/}, {_id: 0, path: 1})

8. Adding to Cart

9. Cart, example schema
{
_id: "the_users_session_id",
status:'active'
quantity: 2,
total: 2000,
products: []
}
• Add item to cart
• Update inventory only if we have enough quantity
• Rollback if inventory update fails

10. Cart, add item to cart
db.carts.update({
_id: "the_users_session_id", status:'active'
}, {
$set: { modified_on: ISODate() },
$push: {
products: {
sku: "111445GB3", quantity: 1, title: "Simsong One mobile
phone", price:1000
}
}
});
{
_id: "the_users_session_id",
status:'active'
quantity: 2,
total: 2000,
products: [{sku: "111445GB3", quantity: 1, title: "Simsong One mobile
phone", price:1000}]
}

11. Cart, add to cart, inventory cover
db.products.update({
sku: "111445GB3", quantity: {$gte: 1}
}, {
$inc: {quantity: -1},
$push: {
in_carts: {
quantity:1, id: "the_users_session_id", timestamp: new
ISODate()
}
}
• If we did not update the stock, roll back cart add
if(!db.runCommand({getLastError:1}).updatedExisting) {
db.carts.update({
_id: "the_users_session_id"
}, {
$pull: {products: {sku:"111445GB3"}}
})
}

12. Update Cart

13. Cart, update quantity
db.carts.update({
_id: "the_users_session_id", "products.sku": "111445GB3", status:
"active"
}, {
$set: {
modified_on: new ISODate(),
"products.$.qty": new_quantity
}
})
• Update the quantity in the cart
• new_quantity = 2
• old_quantity = 1
• delta_quantity = new_quantity - old_quantity

14. Cart, update inventory
db.products.update({
sku: "111445GB3",
"in_carts.id": "the_users_session_id",
quantity: {
$gte: 1
}
}, {
$inc: { quantity: (-1)*delta_quantity },
$set: {
"in_carts.$.quantity": new_quantity, timestamp: new ISODate()
}
})
• Attempt to update the inventory
• new_quantity = 2
• old_quantity = 1
• delta_quantity = new_quantity - old_quantity

15. Cart, on failure rollback
if(!db.runCommand({getLastError:1}).updatedExisting) {
db.carts.update({
_id: "the_users_session_id", "products.sku": "111445GB3"
}, {
$set : { "in_carts.$.quantity": old_quantity}
})
}
• If the update fails roll back the cart to the previous
quantity
• new_quantity = 2
• old_quantity = 1
• delta_quantity = new_quantity - old_quantity

16. Expire Carts

17. Cart, expire all the carts
var carts = db.carts.find({status:"expiring"})
for(var i = 0; i < carts.length; i++) {
var cart = carts[i]
for(var j = 0; j < cart.products.length; j++) {
var product = cart.products[i]
db.products.update({
sku: product.sku,
"in_carts.id": cart._id,
"in_carts.quantity": product.quantity
}, {
$inc: {quantity: item.quantity},
$pull: {in_carts: {id: cart._id}}
})
}
db.carts.update({
_id: cart._id,
$set: {status: 'expired'}
})
}

18. Checkout

19. Insert an Order
db.orders.insert({
created_on: new ISODate("2012-05-17T08:14:15.656Z"),
shipping: {
customer: "Peter P Peterson",
address: "Longroad 1343",
city: "Peterburg",
region: "",
state: "PE",
country: "Peteonia",
delivery_notes: "Leave at the gate",
tracking: {
company: "ups", tracking_number: "22122X211SD",
status: "ontruck",
estimated_delivery: new ISODate("2012-05-17T08:14:15.656Z")
},
},
payment: { method: "visa", transaction_id: "2312213312XXXTD" }
products: {
{quantity: 2, sku:"111445GB3", title: "Simsong mobile phone",
unit_cost:1000, currency:"USD"}
}
})

20. Cart, finish up and clean up
db.carts.update({
_id: "the_users_session_id"
}, {
$set: {status:"complete"}
});
• Set the cart status as completed
db.products.update({
"in_carts.id": "the_users_session_id"
}, {
$pull: {in_carts: {id: "the_users_session_id"}}
}, false, true);
• Remove all carts from products

21. Thank you and happy
schemaing
twitter: @christkv