Question

I have this SQL query in my DB which is causing a problem with PostgreSQL on heroku, Causing the page not to load with the above error in the heroku logs. I am using postgreSQL 9.1.6 so previous bugs have apparently been fixed

def self.top_countries
joins(:recipes).
  select('countries.*, count(*) AS recipes_count').
  group('countries.id').
  order('recipes_count DESC')

end

I am unsure on how to refactor this so that it will work.Could anyone advise please?

Thank You

Answer 1

def self.top_countries
joins(:recipes).
  select('countries.id, count(*) AS recipes_count').
  group('countries.id').
  order('recipes_count DESC')

This generates the SQL

select countries.id, count(*) AS recipes_count
  from countries
  join recipes on countries.id = recipes.country_id
 group by countries.id
 order by recipes_count

You’ll notice that you only have 2 columns in the SELECT.
Not being a Heroku expert, I suspect you can get it to work by explicitly listing all column that you need from countries, and grouping by the full column list i.e.

def self.top_countries
joins(:recipes).
  select('countries.id, countries.name, countries.other, count(*) AS recipes_count').
  group('countries.id, countries.name, countries.other').
  order('recipes_count DESC')

There might be a more concise way to join the original answer (top part) with another join to top_countries on countries.id to get the rest of the columns after the group by.