sum hash values inside db column and place result in another - ruby-on-rails

Question

I have a table called google_records in which every row is a snapshot of a google adwords account for that day.
Here is the schema -
create_table "google_records", :force => true do |t|
t.string "user_id"
t.string "date"
t.text "stats"
t.text "account_name"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
t.decimal "total_cost", :precision => 12, :scale => 2, :default => 0.0, :null => false
t.integer "total_conversions", :default => 0, :null => false
end
add_index "google_records", ["date"], :name => "index_google_records_on_date"
stats contains a hash of the day's stats by campaign and an entry would look something like this:
:Carpet Cleaning:
:conversions: 3
:cost: 391.47
:Upholstery Cleaning:
:conversions: 0
:cost: 69.96
:Air Duct Cleaning:
:conversions: 0
:cost: 8.68
I just added those total_cost and total_conversion columns and I'd like to update those with the totals for each respective value each day.
I can get the total I want to work in my console like so(the cost total doesn't match up with the sample I gave but its only because I shortened the sample to fit better - the total is correct) -
user = User.find(6)
GoogleRecord.where(user_id: user).where(date: "20140328").map {|m| m.stats}.map{ |s| s.map{ |key, value| value[:cost] || 0 } }.map {|m| m.inject(:+)}.compact.reduce(&:+)
=> 660.26
I'd like to update all records in the table this way for conversions and cost and save them but when I try something like:
GoogleRecord.all.each do |g|
g.map {|m| m.stats}.map{ |s| s.map{ |key, value| value[:cost] || 0 } }.map {|m| m.inject(:+)}.compact.reduce(&:+)
end
I keep getting NoMethodError: undefined method map for GoogleRecord:0x5f09868
It seems like since I'm just grabbing one record in the example that is working, I should be able to apply code to each record.

Answer 1

Inside your example code, what the where method return is something like array, so map can work. But inside the GoogleRecord.all.each block, the g is reference to the db record. Remove the first map call, and see whether it will work.
GoogleRecord.all.each do |g|
g.stats.map{ |s| s.map{ |key, value| value[:cost] || 0 } }.map {|m| m.inject(:+)}.compact.reduce(&:+)
end