TILs - Fueling Curiosity, One Insight at a Time

To generate an Entity-Relationship Diagram (ERD) using Prisma-erd-generator, follow these steps :
• Install the following package



• Add this to your schema.prisma



• Run the generator



#javascript #erd

To use Client Components, states, useState, useEffect, onClick, and other client-side features, add "use client" at the top of your file. This ensures the component runs on the client side.

#javascript #nextjs

Key difference between App router and Page router :

App Router:
• File-based routing: Uses nested folders to define routes.
• Components: Server Components by default.
• Data fetching: Uses fetch function.
• Layouts: Can be nested and dynamic.
• Dynamic routes: Supported, but syntax differs.
• Client-side navigation: Supported with router.push.
• Priority: Takes precedence over Page Router.
Page Router:
• File-based routing: Files directly represent routes.
• Components: Client Components by default.
• Data fetching: Uses getServerSideProps, getStaticProps, getInitialProps.
• Layouts: Static.
• Dynamic routes: Supported.
• Client-side navigation: Supported with Link component.
• Priority: Fallback if no matching route in App Router.
#javascript #nextjs

How to schedule tasks using cron expressions in GitHub Actions:
By defining a cron schedule in the workflow YAML file, we can automate the execution of tasks at specific intervals.
For instance, setting */5 * * * * in the cron expression triggers the workflow every 5 minutes.
Monitoring workflow runs in the "Actions" tab of the GitHub repository allows to verify that the scheduled tasks are executing as intended.
#cronjobs #workflowautomation

When terraform state file is locked and you are unable to acquire a state lock, you can use terraform force-unlock <LOCK_ID> to forcefully remove the lock.
#terrafrom

Use git reset --mixed HEAD~1 command to undo your last commit without losing the changes made in your last commit.

#git #gitReset #github

In TypeScript interfaces, ?: denotes optional properties. Here's an example:




#javascript #typescript

Utility Types:
TypeScript's Utility Types simplify complex type manipulations. For instance, Partial<T> makes all properties of type T optional




#javascript #typescript

EAGER LOADING

Eager loading in Rails is a technique used to optimize database queries by loading associated records of the objects returned by the query, thereby reducing the number of database calls. This is particularly useful when you have associations defined in your models and you want to avoid the "N+1 query problem."

What is the N+1 Query Problem?

“N+1 Queries” are a very common cause of repeated queries in Rails applications. This happens when you make a request for a single row in one table, and then make an additional request per element in a has_many relationship, usually in a loop.
Here’s an example:

Consider two models: Author and Book, where an Author has many Books.






Scenario Without Eager Loading
When you fetch authors and then access their books, Rails performs an additional query for each author to get their books.



This will result in one query to fetch the authors and multiple queries to fetch books for each author, leading to the N+1 query problem.

How Eager Loading Works

Eager loading addresses this problem by loading all the necessary data in as few queries as possible, usually through the use of includes, eager_load, or preload.

Using Eager Loading with includes

To avoid the N+1 query problem, you can use includes to preload the associated books when fetching authors.



With includes, Rails performs a single query to fetch all authors and another single query to fetch all associated books.

Using Eager Loading with eager_load

eager_load forces Rails to use a SQL JOIN to load the associated records. This can be useful if you need to filter or sort based on the associated records.



This approach performs a single query with a LEFT OUTER JOIN.

Using Eager Loading with preload

preload is similar to includes, but it always uses separate queries for loading the associations.



preload is useful when you know that separate queries will be more efficient, for example, when fetching a large number of records.

Summary

Eager loading is a powerful tool in Rails that helps to optimize database access by pre-loading associations. Using includes, eager_load, or preload appropriately can significantly improve the performance of your application by reducing the number of database queries.

#rails #db #optimizing_queries

Scoped Associations with Joins

Let's consider the following models:
• Author with attributes id, name
• Book with attributes id, title, published, author_id
The association is that an Author has many Books, and a Book belongs to an Author.

Defining Scoped Associations
First, let's define a scope on the Book model to filter only published books:



Next, let's use this scope in the Author model to create a scoped association:




Now, Author has an association called published_books, which only includes books that are published.

Using Scoped Associations with Joins

We can now use the scoped association in joins to fetch authors and their published books.
Example 1: Fetch Authors with Published Books
To fetch authors along with their published books:




This query joins the authors table with the books table but only includes books that are published, thanks to the scoped association published_books.

As a result, each Author object in @authors_with_published_books will have:
• All attributes of the Author model.
• An additional attribute called book_title representing the title of each associated book.
#rails #scoped_associations_with_joins