In Rails 3 data save with out p() - ruby-on-rails-3

Question

In the below code retrive data from database arrange those & delete from database again insert
page_nos = [10,11,12,13,14,20,21,22,23,24,30,31,32,33,34,40,41,42,43,44]
page_nos.each do |page|
#page_data = HomePageSetting.where("page_no = '#{page}'").order("score desc")
p(#page_data)
HomePageSetting.where("page_no = #{page}").delete_all
#page_data.each do |data|
#home_page = HomePageSetting.new
#home_page.subject_id = data.subject_id
#home_page.subject_type = data.subject_type
#home_page.score = data.score
#home_page.flag = data.flag
#home_page.flag_detail = data.flag_detail
#home_page.page_no = data.page_no
#home_page.release_date = data.release_date
#home_page.item_created_at = data.item_created_at
#home_page.save
end
end
that is not working if i remove p(#page_data) line

Answer 1

I don't quite understand what you're trying to do, but I suspect I do know the reason that outputting the #page_data variable makes a difference.
#page_data is an ActiveRecord::Relation object - that is, a stored SQL query. Because executing a query and loading the resulting objects into memory takes time, Rails doesn't actually execute the query until it has to. When you output #page_data, its has to instantiate those objects to print the output. They then exist in memory, and can be referenced even after you delete their rows from the database in the next line.
If you don't print out that data, it stays uninstantiated on the next line, where you delete all those rows. Then, you call .each on it, and it gets instantiated at that point, and there are no objects to fetch, because you just deleted them all.
You can force Rails to instantiate the relation when you first define #page_data by calling .all, on it, thus:
#page_data = HomePageSetting.where("page_no = '#{page}'").order("score desc").all

Answer 2

It looks as if one problem at least is that you're calling .save inside the .new block -- you should save the record after.
Here's the changed code:
page_nos = [10,11,12,13,14,20,21,22,23,24,30,31,32,33,34,40,41,42,43,44]
page_nos.each do |page|
#page_data = HomePageSetting.where("page_no = '#{page}'").order("score desc")
p(#page_data)
HomePageSetting.where("page_no = #{page}").delete_all
#page_data.each do |data|
#home_page = HomePageSetting.new
#home_page.subject_id = data.subject_id
#home_page.subject_type = data.subject_type
#home_page.score = data.score
#home_page.flag = data.flag
#home_page.flag_detail = data.flag_detail
#home_page.page_no = data.page_no
#home_page.release_date = data.release_date
#home_page.item_created_at = data.item_created_at
end
#home_page.save
end
When I'm having problems like this I also sometimes will use .save! -- it will halt processing and throw an exception if the data doesn't save correctly. .save can fail silently and simply return false. To try that use #home_page.save! instead.
Good luck!