Heroku PG::UndefinedColumn: ERROR does not exist - ruby-on-rails

Question

This runs fine on the rails server but doesn't work on Heroku and says something went wrong etc. This basically happens when I search for b_pages via BPage_name:
Schema:
create_table "b_pages", force: :cascade do |t|
t.string "Bpage_name"
t.string "first_post"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "profile_img_file_name"
t.string "profile_img_content_type"
t.integer "profile_img_file_size"
t.datetime "profile_img_updated_at"
t.string "banner_img_file_name"
t.string "banner_img_content_type"
t.integer "banner_img_file_size"
t.datetime "banner_img_updated_at"
t.integer "user_id"
t.string "status"
t.text "bio"
t.string "relationship"
t.text "whitelist"
t.text "blacklist"
end
b_page.rb:
def self.search(query)
where("Bpage_name like ?", "%#{query.downcase}%")
end

Answer 1

Identifiers (such as table and column names) are case insensitive in SQL. However, if you double quote them when you create the table then they are case sensitive. Standard SQL folds unquoted identifiers to upper case but PostgreSQL folds them to lower case, hence the complain about bpage_name being an unknown column when you say:
where("Bpage_name like ?", "%#{query.downcase}%")
ActiveRecord double quotes all the identifiers when it creates tables so if you have any column names that are case sensitive (such as Bpage_name) then you have to double quote them everywhere you use them in SQL snippets:
where('"Bpage_name" like ?', "%#{query.downcase}%")
# -----^----------^
The recommended practice with PostgreSQL (and Rails/ActiveRecord for that matter) is to use lower case column names with underscores to separate words. Saying this:
t.string "bpage_name"
in your migration would be more consistent with both conventions and would avoid your quoting problem completely.
When you say something like:
where(:Bpage_name => 'pancakes')
ActiveRecord will add the quotes itself and send:
where "Bpage_name" = 'pancakes'
to the database. The quoting and case sensitivity issue only arises when you use bits of SQL; of course, you almost always end up using SQL snippets with ActiveRecord so the naming convention is still important if you don't want to litter your code with a bunch of noisy double quotes.