Download as PDF, PPTX
![Show me a document
{
"name" : "Matias Cascallares",
"title" : "Senior Solutions Architect",
"email" : "matias@mongodb.com",
"birth_year" : 1981,
"location" : [ "Singapore", "Asia"],
"phone" : {
"type" : "mobile",
"number" : "+65 8591 3870"
}
}](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-5-2048.jpg)
![Let’s use the document model
> db.user.findOne( { email: "kate.powell@somedomain.com"} )
{
_id: 1,
name: "Kate Powell",
email: "kate.powell@somedomain.com",
title: "Regional Manager",
addresses: [
{ street: "123 Sesame St", city: "Boston" },
{ street: "123 Evergreen St", city: "New York" }
]
}](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-19-2048.jpg)
![Embedding tasks
> db.user.findOne( { email: "kate.powell@somedomain.com"} )
{
name: "Kate Powell",
// ... previous fields
tasks: [
{
summary: "Contact sellers",
description: "Contact agents to specify our needs
and time constraints",
due_date: ISODate("2014-08-25T08:37:50.465Z"),
status: "NOT_STARTED"
},
{ // another task }
]
}](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-21-2048.jpg)
![Referencing tasks
> db.user.findOne({_id: 1})
{
_id: 1,
name: "Kate Powell",
email: "kate.powell@...",
title: "Regional Manager",
addresses: [
{ // address 1 },
{ // address 2 }
]
}
> db.task.findOne({user_id: 1})
{
_id: 5,
summary: "Contact sellers",
description: "Contact agents
to specify our ...",
due_date: ISODate(),
status: "NOT_STARTED",
user_id: 1
}](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-23-2048.jpg)
![List of sorted elements
> db.numbers.insert({
_id: "even",
values: [0, 2, 4, 6, 8]
});
> db.numbers.insert({
_id: "odd",
values: [1, 3, 5, 7, 9]
});](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-32-2048.jpg)
![Access based on position
db.numbers.find({_id: "even"}, {values: {$slice: [2, 3]}})
{
_id: "even",
values: [4, 6, 8]
}
db.numbers.find({_id: "odd"}, {values: {$slice: -2}})
{
_id: "odd",
values: [7, 9]
}](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-33-2048.jpg)
![Access based on values
// is number 2 even or odd?
> db.numbers.find( { values : 2 } )
{
_id: "even",
values: [0, 2, 4, 6, 8]
}](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-34-2048.jpg)
![Like sorted sets
> db.numbers.find( { _id: "even" } )
{
_id: "even",
values: [0, 2, 4, 6, 8]
}
> db.numbers.update(
{ _id: "even"},
{ $addToSet: { values: 10 } }
);
Several times…!
> db.numbers.find( { _id: "even" } )
{
_id: "even",
values: [0, 2, 4, 6, 8, 10]
}](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-35-2048.jpg)
![Storage
DocA DocB DocC
{
_id: 1,
name: "Nike Pump Air 180",
tags: ["sports", "running"]
}
db.inventory.update(
{ _id: 1},
{ $push: { tags: "shoes" } }
)](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-38-2048.jpg)
![Products and comments
> db.product.find( { _id: 1 } )
{
_id: 1,
name: "Nike Pump Air Force 180",
tags: ["sports", "running"]
}
> db.comment.find( { product_id: 1 } )
{ score: 5, user: "user1", text: "Awesome shoes" }
{ score: 2, user: "user2", text: "Not for me.." }](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-47-2048.jpg)
![Denormalizing
> db.product.find({_id: 1})
{
_id: 1,
name: "Nike Pump Air Force 180",
tags: ["sports", “running"],
comments: [
{ user: "user1", text: "Awesome shoes" },
{ user: "user2", text: "Not for me.." }
]
}
> db.comment.find({product_id: 1})
{ score: 5, user: "user1", text: "Awesome shoes" }
{ score: 2, user: "user2", text: "Not for me.."}](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-48-2048.jpg)
![Bucketing comments
> db.comments.find({post_id: 123})
.sort({sequence: -1})
.limit(1)
{
_id: 1,
post_id: 123,
sequence: 8, // this acts as a page number
comments: [
{user: user1@somedomain.com, text: "Awesome shoes.."},
{user: user2@somedomain.com, text: "Not for me..”}
] // we store two comments per doc, fixed size bucket
}](https://image.slidesharecdn.com/mongodbschemadesign-141123033635-conversion-gate01/75/The-Fine-Art-of-Schema-Design-in-MongoDB-Dos-and-Don-ts-54-2048.jpg)
Uploaded byMatias Cascallares
The Fine Art of Schema Design in MongoDB: Dos and Don'ts
The document discusses best practices for schema design in MongoDB, focusing on its flexible document-oriented structure versus traditional relational databases. It emphasizes the importance of embedding versus referencing documents based on the relationship types, the benefits of using arrays, and techniques like denormalization and bucketing to optimize performance. Several specific examples illustrate how to design effective schemas for tasks such as tracking user information and managing tasks.
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The Fine Art of Schema Design in MongoDB: Dos and Don'ts
- 1. The Fine Artof Schema Design: Dos and Don'ts Matias Cascallares Senior Solutions Architect, MongoDB Inc. [email protected]
- 2. Who am I? • Originally from Buenos Aires, Argentina • Solutions Architect at MongoDB Inc based in Singapore • Software Engineer, most of my experience in web environments • In my toolbox I have Java, Python and Node.js
- 3. RDBMs • Relationaldatabases are made up of tables • Tables are made up of rows: • All rows have identical structure • Each row has the same number of columns • Every cell in a column stores the same type of data
- 4. MONGODB IS A DOCUMENT ORIENTED DATABASE
- 5. Show me adocument { "name" : "Matias Cascallares", "title" : "Senior Solutions Architect", "email" : "[email protected]", "birth_year" : 1981, "location" : [ "Singapore", "Asia"], "phone" : { "type" : "mobile", "number" : "+65 8591 3870" } }
- 6. Document Model •MongoDB is made up of collections • Collections are composed of documents • Each document is a set of key-value pairs • No predefined schema • Keys are always strings • Values can be any (supported) data type • Values can also be an array • Values can also be a document
- 7. Benefits of document model ..?
- 8. Flexibility • Eachdocument can have different fields • No need of long migrations, easier to be agile • Common structure enforced at application level
- 9. Arrays • Documentscan have field with array values • Ability to query and index array elements • We can model relationships with no need of different tables or collections
- 10. Embedded documents •Documents can have field with document values • Ability to query and index nested documents • Semantic closer to Object Oriented Programming
- 11. Indexing an arrayof documents
- 12. Relational Schema Design Document Schema Design
- 13. Relational Schema Design Focus on data storage Document Schema Design Focus on data usage
- 14. SCHEMA DESIGN IS AN ART https://www.flickr.com/photos/76377775@N05/11098637655/
- 15.
- 16.
- 17. Requirement #1 "Weneed to store user information like name, email and their addresses… yes they can have more than one.” — Bill, a project manager, contemporary
- 18. Relational id nameemail title 1 Kate Powell [email protected] om Regional Manager id street city user_id 1 123 Sesame Street Boston 1 2 123 Evergreen Street New York 1
- 19. Let’s use thedocument model > db.user.findOne( { email: "[email protected]"} ) { _id: 1, name: "Kate Powell", email: "[email protected]", title: "Regional Manager", addresses: [ { street: "123 Sesame St", city: "Boston" }, { street: "123 Evergreen St", city: "New York" } ] }
- 20. Requirement #2 "Wehave to be able to store tasks, assign them to users and track their progress…" — Bill, a project manager, contemporary
- 21. Embedding tasks >db.user.findOne( { email: "[email protected]"} ) { name: "Kate Powell", // ... previous fields tasks: [ { summary: "Contact sellers", description: "Contact agents to specify our needs and time constraints", due_date: ISODate("2014-08-25T08:37:50.465Z"), status: "NOT_STARTED" }, { // another task } ] }
- 22. Embedding tasks •Tasks are unbounded items: initially we do not know how many tasks we are going to have • A user along time can end with thousands of tasks • Maximum document size in MongoDB: 16 MB ! • It is harder to access task information without a user context
- 23. Referencing tasks >db.user.findOne({_id: 1}) { _id: 1, name: "Kate Powell", email: "kate.powell@...", title: "Regional Manager", addresses: [ { // address 1 }, { // address 2 } ] } > db.task.findOne({user_id: 1}) { _id: 5, summary: "Contact sellers", description: "Contact agents to specify our ...", due_date: ISODate(), status: "NOT_STARTED", user_id: 1 }
- 24. Referencing tasks •Tasks are unbounded items and our schema supports that • Application level joins • Remember to create proper indexes (e.g. user_id)
- 25.
- 26. One-to-many relations •Embed when you have a few number of items on ‘many' side • Embed when you have some level of control on the number of items on ‘many' side • Reference when you cannot control the number of items on the 'many' side • Reference when you need to access to ‘many' side items without parent entity scope
- 27. Many-to-many relations •These can be implemented with two one-to-many relations with the same considerations
- 28. RECIPE #1 USEEMBEDDING FOR ONE-TO-FEW RELATIONS
- 29. RECIPE #2 USEREFERENCING FOR ONE-TO-MANY RELATIONS
- 30. Working with arrays https://www.flickr.com/photos/kishjar/10747531785
- 31.
- 32. List of sortedelements > db.numbers.insert({ _id: "even", values: [0, 2, 4, 6, 8] }); > db.numbers.insert({ _id: "odd", values: [1, 3, 5, 7, 9] });
- 33. Access based onposition db.numbers.find({_id: "even"}, {values: {$slice: [2, 3]}}) { _id: "even", values: [4, 6, 8] } db.numbers.find({_id: "odd"}, {values: {$slice: -2}}) { _id: "odd", values: [7, 9] }
- 34. Access based onvalues // is number 2 even or odd? > db.numbers.find( { values : 2 } ) { _id: "even", values: [0, 2, 4, 6, 8] }
- 35. Like sorted sets > db.numbers.find( { _id: "even" } ) { _id: "even", values: [0, 2, 4, 6, 8] } > db.numbers.update( { _id: "even"}, { $addToSet: { values: 10 } } ); Several times…! > db.numbers.find( { _id: "even" } ) { _id: "even", values: [0, 2, 4, 6, 8, 10] }
- 36. Array update operators • pop • push • pull • pullAll
- 37.
- 38. Storage DocA DocBDocC { _id: 1, name: "Nike Pump Air 180", tags: ["sports", "running"] } db.inventory.update( { _id: 1}, { $push: { tags: "shoes" } } )
- 39. Empty Storage DocADocB DocC IDX IDX IDX
- 40. Empty Storage DocADocC DocB IDX IDX IDX
- 41. Why is expensiveto move a doc? 1. We need to write the document in another location ($$) 2. We need to mark the original position as free for new documents ($) 3. We need to update all those index entries pointing to the moved document to the new location ($$$)
- 42. Considerations with arrays • Limited number of items • Avoid document movements • Document movements can be delayed with padding factor • Document movements can be mitigated with pre-allocation
- 43. RECIPE #3 AVOIDEMBEDDING LARGE ARRAYS
- 44. RECIPE #4 USEDATA MODELS THAT MINIMIZE THE NEED FOR DOCUMENT GROWTH
- 45.
- 46. Denormalization "…is theprocess of attempting to optimise the read performance of a database by adding redundant data …” — Wikipedia
- 47. Products and comments > db.product.find( { _id: 1 } ) { _id: 1, name: "Nike Pump Air Force 180", tags: ["sports", "running"] } > db.comment.find( { product_id: 1 } ) { score: 5, user: "user1", text: "Awesome shoes" } { score: 2, user: "user2", text: "Not for me.." }
- 48. Denormalizing > db.product.find({_id:1}) { _id: 1, name: "Nike Pump Air Force 180", tags: ["sports", “running"], comments: [ { user: "user1", text: "Awesome shoes" }, { user: "user2", text: "Not for me.." } ] } > db.comment.find({product_id: 1}) { score: 5, user: "user1", text: "Awesome shoes" } { score: 2, user: "user2", text: "Not for me.."}
- 49. RECIPE #5 DENORMALIZE TO AVOID APP-LEVEL JOINS
- 50. RECIPE #6 DENORMALIZEONLY WHEN YOU HAVE A HIGH READ TO WRITE RATIO
- 51.
- 52. What’s the idea? • Reduce number of documents to be retrieved • Less documents to retrieve means less disk seeks • Using arrays we can store more than one entity per document • We group things that are accessed together
- 53. An example Commentsare showed in buckets of 2 comments A ‘read more’ button loads next 2 comments
- 54. Bucketing comments >db.comments.find({post_id: 123}) .sort({sequence: -1}) .limit(1) { _id: 1, post_id: 123, sequence: 8, // this acts as a page number comments: [ {user: [email protected], text: "Awesome shoes.."}, {user: [email protected], text: "Not for me..”} ] // we store two comments per doc, fixed size bucket }
- 55. RECIPE #7 USEBUCKETING TO STORE THINGS THAT ARE GOING TO BE ACCESSED AS A GROUP
- 56.