Objection.js, a SQL ORM

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Objection.js a SQL ORM Paul Jensen

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HELLO ITS ME AGAIN!

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Node.js has plenty of ORMs

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Why consider another?

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Sometimes a fresh take on an existing challenge can oﬀer something better

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So for your consideration, I oﬀer you this…

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Objection.js github.com/vincit/objection.js

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Objection.js • Let’s you create models for tables with ES6 classes and deﬁne relationships between them • Make queries with Node’s async/await • Add validation to your models using JSON schema • Use eager-loading and transactions with your models • Work with nested documents in rows • Perform Graph Inserts and Upserts • and more…

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Install

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Knex knexjs.org

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Knex • Rather than reinvent the wheel, Objection uses Knex, a powerful SQL query builder. • Besides building SQL queries, Knex is used to establish database connections, including pooling connections. • Also, it is used for managing database schemas via migrations.

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Install a DB driver as well

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Creating and managing database schemas

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Creating and managing database schemas • Database migrations are a good pattern for managing changes to database schemas over time. • Objection.js defers to Knex for doing database migrations. • Knex depends on connecting to an existing database, so we’d need to create that ﬁrst (unless it exists already).

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Creating a database

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Creating migrations • Migrations allow you to apply a change to a database schema in a step-by-step fashion. • The “up” action applies a change (creating a table, adding or modifying a column, appending an index). • The “down” action applies the reverse action of the change (e.g. if a migration’s “up” action creates a table, it’s equivalent “down” action will drop the table). • It provides a way to evolve a database schema over time, and be able to track the state of the database schema alongside the source code in version control (Git).

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Creating migrations • Objection uses Knex’s in-built support for generating migrations and applying them, as well as being able to roll them back.

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Creating migrations

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Creating migrations

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Creating migrations • Knex will create a migrations folder (unless it exists already) • It then creates a ﬁle in the migrations folder for the migration • The ﬁlename from the command line is prepended with a timestamp so that we can organise migrations in chronological order. • That determines the order in which migrations are executed.

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The generated migration

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Apply the migration

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Apply the migration

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Reversing the migration

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Reversing the migration

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Models

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Models • Models are the wrappers around database tables • They help to encapsulate the business logic within those tables (relations, validations, indexes, triggers). • Objection.js allows you to create Models using ES classes

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Task model

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Queries

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A simple SELECT query can be done with…

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A more typical SELECT query can be done with…

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INSERT queries can be done with…

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UPDATE queries can be done with…

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DELETE queries can be done with…

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Relationships

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Relationships • Objection.js provides a way to deﬁne the relationship between models that is powerful and ﬂexible. • The relationships allow you to use other features like eager loading, as well as support Objection.js’ GraphQL plugin.

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Relationships tasks id name due_by is_done created_at updated_at task_joins id dependent_id dependency_id created_at updated_at 1 ∞ ∞

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You can also specify relationships through join tables

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Example: Doing the dishes

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Eager Loading

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Lifecycle functions • A way to trigger functions when a record is inserted, updated, deleted, fetched or validated. • The lifecycle functions follow a pattern of beforeAction and afterAction.

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Lifecycle functions • beforeValidate, afterValidate • beforeInsert, afterInsert • beforeUpdate, afterUpdate • beforeDelete, afterDelete • afterGet

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Lifecycle functions You can execute functions that trigger during the lifecycle of inserting and updating records. You can determine whether they happen before or after the lifecycle event.

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Lifecycle functions You can execute functions that trigger during the lifecycle of inserting and updating records. You can determine whether they happen before or after the lifecycle event.

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Validations

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Validations • Objection allows you to add validation logic to your models through using JSONSchema. • The validation logic will raise errors which can then be intercepted with try/catch

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If you add jsonSchema to your models, you get to use some very cool plugins later on

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Graph Inserts

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Graph Inserts are cool

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Quick demo

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Plugins

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Plugins • Objection comes with a few plugins that are worth checking out • Two which I can recommend are “objection-graphql” and “objection-password”

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Objection-Password • Objection password adds quick local authentication to an application, using Bcrypt to apply the salting and hashing. • Setting it up is very simple - simply specify the number of hashing rounds for encrypting the password, and make your User model an extended class of the Password class

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Objection-GraphQL • Objection-GraphQL allows you to put a GraphQL API on top of your Objection.js models with a few lines of code. • You will need to have your models using JSONSchema in order to get the beneﬁts of this.