Fueling Curiosity, One Insight at a Time

In Rails we can do two modes of locking that is 'Optimistic Locking' and 'Pessimistic locking'. 'Optimistic Locking' assumes that a database transaction conflict is very rare to happen and such locked records can still be read (Shared lock). It uses a version number of the record to track the changes. This can be used by adding a lock_version column to the table and then is handled automatically by Rails.
Whereas 'Pessimistic locking' assumes that database transaction conflict is very likely to happen. It locks the record until the transaction is done (Exclusive lock). This can be done with ActiveRecord::Base#lock! or ActiveRecord::Locking::Pessimistic#with_lock.

a decent spreadsheet writer gem for ruby, https://github.com/felixbuenemann/xlsxtream, ran some rough benchmarks, and this one is the fastest and lowest memory consuming gem. although not feature complete.

This is a good read about common Rails errors which rollbar has captured https://rollbar.com/blog/top-10-ruby-on-rails-errors/

http://api.rubyonrails.org/v5.0/classes/ActiveRecord/QueryMethods.html#method-i-left_joins since rails 5

row caching and stream: true option for mysql2 https://github.com/brianmario/mysql2#row-caching

there are command-line options which you can add to bash scripts, can be added in the header like #!/bin/bash -e

set -x is very useful while writing shell scripts. It echos commands being run (even in for loops) which helps in debugging. Put this at the top of script file, and see the magic!

http://jsnice.org/ not a TIL, but lost and found it only today. This is a reverse tool that can be run on minified JS to get some more human readable ouput

You can scope relations like has_many, has_one and belongs_to. Eg: has_one :policy, -> { where active: true }