Exception ActiveRecord::StatementInvalid doesn't works - mysql

Question

I'm relative new to Rails, so I don't know if my way to solve the problem is the correct, but there's some problem with it
I have installed in my PC MySQL, but Heroku uses PostgreSQL, so I'm designing a solution to work with both DBMS in certain problem.
I have the next code:
begin
#products_with_valid_offers = Product.joins(:variants).active.discount_valid.discount_date_valid_mySQL
rescue ActiveRecord::StatementInvalid
#products_with_valid_offers = Product.joins(:variants).active.discount_valid.discount_date_valid_postgreSQL
end
And the scopes are:
scope :active, includes([:assets, :store]).where(:active => true, :deleted_at => nil, :stores => { :deleted_at => nil, :active => true }).order("products.created_at DESC")
scope :discount_date_valid_mySQL, where('DATE_FORMAT(NOW(),"%Y-%m-%d 23:59:59") + '" BETWEEN discount_from AND discount_to')
scope :discount_date_valid_postgreSQL, where('now()::date BETWEEN discount_from AND discount_to')
As you see, I need 2 different forms to manage the date format, one with each DBMS.
The issue is that the flow never enters in the exception. If #products_with_valid_offers is a SQL Error in MySQL, never enters to the rescue block to execute the PostgreSQL line, and it returns an error.
Some help, please?. :D

Answer 1

Your quotes are messed up in discount_date_valid_mySQL, you want to say this:
scope :discount_date_valid_mySQL, where("DATE_FORMAT(NOW(),'%Y-%m-%d 23:59:59') BETWEEN discount_from AND discount_to")
That at least is valid Ruby code.
That said, your current approach is bad in various ways:
You're ensuring that you always have an exception in production.
You're developing on top of one database but deploying on top of another, this alone will cause you all sorts of problems.
You should be using just date_format(now(), '%Y-%m-%d') in your MySQL version.
There are probably other issues but there's no need to spend more time picking apart your code: there is a better way. Both MySQL and PostgreSQL (and even SQLite) support current_date so you can just use one thing for both:
scope :discount_date_valid, where('current_date between discount_from and discount_to')
Assuming of course that you want everything to assume UTC. If you want things to use some other time zone then:
Store your discount_from and discount_to as date columns, dates don't have timezones in SQL. Presumably you're doing this already but I just want to make sure.
Adjust your scope to get the current date from your client code (which is presumably configured to use the right timezone):
def self.discount_date_valid
where(':current_date between discount_from and discount_to', :current_date => Date.today)
end
You have to use a class method for the scope to ensure that Date.today is evaluated at the right time (i.e. when the scope is used instead of when the class is loaded).
And you really should develop on top of PostgreSQL if you're deploying on top of PostgreSQL. You should even make sure you're developing and deploying on the same version of PostgreSQL. Developing on top of one stack and deploying on another causes all sorts of pointless frustration and confusion.