Ruby on Rails-MySQL和PostGres

Question

I'm a RoR begginer and am developing my app using MySQL but Heroku uses Postgres, so my arel isn't working quite properly.

I've searched about the outputted error but in my case, since I'm doing a query between a HABTM table, things aren't going so well.

Basically, a Product has_and_belongs_to_many Categories. , but on deploy a 500 error occurs.

So without further delay, the issue is:

(...previous queries that work good locally and on heroku...)

if params[:fc].present? #(checks if checkboxes have been ticked)

arel=arel.joins('INNER JOIN categories_products ON products.id=categories_products.product_id')

arel=arel.where('categories_products.category_id in (:fc_list)', :fc_list => params[:fc]).uniq

arel=arel.group('product_id').having('count(category_id) = :size', :size => params[:fc].size)

end

So the idea is to allow the user to check a checkbox list and then display all the products that are in the checked categories.

My heroku error is: "products.id" must appear in the GROUP BY clause or be used in an aggregate function.

This tells me the error is the GROUP BY and drom the documentation I read that i must put all the columns here. But since it is a HABTM relation, only other column is there, and when I put it, the arel spots functioning properly.

I know that there are already threads on this but none have fixed my problem.

Thank you in advance.

Regards, Miguel A.

Answer 1

This is related to this:

Heroku (PG::Error: ERROR: column must appear in the GROUP BY clause or be used in an aggregate function

They use an older version of postgres in Heroku that doesn't support what you're trying to do. Using the Heroku Shared PostgreSQL addon can solve the issue.

Although, I would also suggest that your development environment looks as much as possible as the Heroku environment. This means using same versions of rubies and same DB...