TILs - Fueling Curiosity, One Insight at a Time

How to Revoke and Amend the Most Recent Git Commit Message.
To undo the most recent commit, unstage the changes, and update the commit message, follow these steps:

1. Revoke the latest commit and unstage the changes.
git reset HEAD~1

2. Stage the changes again.
git add .

3. Create a new commit with the updated message
git commit -m "New commit message"
(If you just want to change the previous commit message) - git commit --amend

4. Force-push the new commit to the remote repository
git push origin <branch-name> --force

> ⚠️ Use --force cautiously, especially on shared branches, as it rewrites history.

pgvector provides native support for vector similarity search in PostgreSQL. It supports three types of distance metrics, each useful depending on the use case:
• <=> Cosine distance – Measures the angle between two vectors (ignores magnitude). Great for comparing meaning in text (e.g., NLP). Smaller angle = more similar.
• <#> L2 (Euclidean distance) – Measures the straight-line distance between two vectors. Takes both direction and size into account. Good when actual value differences matter (like in image or audio data).
• <-> Inner product – Measures how much two vectors point in the same direction and how large they are. If vectors are normalized (length = 1), it works like cosine similarity. Great for ranking similarity when vectors are preprocessed.

#pgvector #PostgreSQL #VectorSearch #Embeddings

ClickHouse DB

It is a column-oriented database management system designed for online analytical processing (OLAP). It's optimised for real-time analytics on large volumes of data and is known for being fast, highly scalable, and efficient for read-heavy workloads like metrics, logs, events, and other analytical data.

Key features are -
1. Columnar storage : Stores data by columns instead of rows, enabling efficient compression and faster reads.
2. Works super fast : Designed to process billions of rows per second per server.
3. SQL-compatible.
4. Materialized views : For real-time aggregation and data transformation.
#databases #click_house_db #analytics

Validating date and time field in Rails

validates_timeliness gem helps us to check if a date or time field is valid and meets certain conditions — like being in the past, in the future, or within a specific range. It can do following things.
1. Check if a date is valid (e.g., "2025-02-30" is not a valid date).
2. Make sure a date is before or after a certain time as needed.
3. Restrict a field to only accept dates, times or datetimes.
4. Works well with user input in different formats.
For example :



This makes sure start_time is not in the past.

#CU6U0R822 #date_time_validation

friendly_id is a Rails gem that lets you use secure, human-readable slugs instead of record IDs in URLs.
https://github.com/norman/friendly_id
it updates the url
from this :



to this:



#CU6U0R822

rails_representation_url in Rails is used to generate a URL for a variant of an Active Storage image, not the original blob. It's especially useful when we want to apply transformations like resizing or converting image formats on-the-fly.




• image.variant(...) creates a variant of the image, resizing it to a maximum of 300x300 pixels, converting it to WebP format, and reducing its quality for optimization.
• .processed ensures the variant is actually processed before generating the URL.
• rails_representation_url(...) then generates the URL for this transformed version.
• only_path: true returns a relative path (instead of a full URL), which is often preferred in views or frontend routing.
This is a great way to deliver performance-optimized images for the UI

#rubyonrails

Rails provides a https://api.rubyonrails.org/classes/ActiveRecord/TokenFor.html#method-i-generate_token_for|generates_token_for method on Active Record models, which can generate unique tokens for records — including support for expiration. This is useful for scenarios like creating unique unsubscribe links in emails. You can later retrieve a record using the generated token with the corresponding https://api.rubyonrails.org/classes/ActiveRecord/TokenFor/RelationMethods.html#method-i-find_by_token_for|find_by_token_for method.

The Rails Authentication generator utilizes this feature in its password reset flow. It uses https://api.rubyonrails.org/classes/ActiveModel/SecurePassword/ClassMethods.html#method-i-has_secure_password|has_secure_password, which by default enables password reset functionality for the user model. When you call the password_reset_token instance method on a user, it internally uses generates_token_for to generate a unique token. You can then find the user record later using find_by_password_reset_token.

By default, https://api.rubyonrails.org/classes/ActiveModel/SecurePassword/ClassMethods.html#method-i-has_secure_password|has_secure_password uses the password attribute, but you can customize this by specifying a different attribute via the attribute option. If you want to disable password reset functionality, you can pass reset_token: false to has_secure_password (it is enabled by default). Similarly, you can disable password confirmation validations by passing validations: false (validations are enabled by default).

#rubyonrails #ror #authentication #token #password

In recent versions of Rails, the default host for the test environment has changed from https://www.example.com|www.example.com to https://example.com|example.com. However, Capybara continues to use https://www.example.com|www.example.com in most cases, which can cause URL assertions in ActionMailer tests to fail when relying on the default settings. To resolve this inconsistency, you can explicitly set default_url_options[:host] to https://www.example.com|www.example.com in test.rb.
#RubyOnRails #ROR #ActionMailer #Capybara #TDD

SEO Best Practices:
• Meta titles should be between 50–60 characters long (including spaces).
• Meta descriptions should be between 120–160 characters (including spaces).
• Use a single H1 tag per page, followed by a clear and consistent hierarchy of H2 and H3 tags across all pages.
• All images should have meaningful alt tags for accessibility and SEO.
• Ensure there are no broken links; tools like Screaming Frog can help detect them.
• Include canonical tags to avoid duplicate content issues.
• Add social meta tags (Open Graph, Twitter Cards) for better link previews.
• The site should have a robots.txt file and a sitemap.xml for better crawling and indexing.
#SEOBestPractices #SearchEngineOptimization

In Rails, default_scope is a way to automatically apply a query condition to every query for a model.
When we define a default_scope, it always gets added unless we manually remove it.

Example:



This ensures a consistent ordering across the app without needing to manually add .order(created_at: :asc) every time.
It's especially useful when displaying comments, messages, tasks, or anything that should appear in the order they were created.

Caution:
default_scope can sometimes be annoying if we want a different order temporarily.
In that case, we would need to call .unscope(:order) to remove it manually.

#rubyonrails