Rails 4 LIKE query - ActiveRecord adds quotes

ActiveRecord is clever enough to know that the parameter referred to by the ? is a string, and so it encloses it in single quotes. You could as one post suggests use Ruby string interpolation to pad the string with the required % symbols. However, this might expose you to SQL-injection (which is bad). I would suggest you use the SQL CONCAT() function to prepare the string like so:

"name LIKE CONCAT('%',?,'%') OR postal_code LIKE CONCAT('%',?,'%')", search, search)

While string interpolation will work, as your question specifies rails 4, you could be using Arel for this and keeping your app database agnostic.

def self.search(query, page=1)
  query = "%#{query}%"
  name_match = arel_table[:name].matches(query)
  postal_match = arel_table[:postal_code].matches(query)
  where(name_match.or(postal_match)).page(page).per_page(5)
end

Your placeholder is replaced by a string and you're not handling it right.

Replace

"name LIKE '%?%' OR postal_code LIKE '%?%'", search, search

with

"name LIKE ? OR postal_code LIKE ?", "%#{search}%", "%#{search}%"

Instead of using the conditions syntax from Rails 2, use Rails 4's where method instead:

def self.search(search, page = 1 )
  wildcard_search = "%#{search}%"

  where("name ILIKE :search OR postal_code LIKE :search", search: wildcard_search)
    .page(page)
    .per_page(5)
end

NOTE: the above uses parameter syntax instead of ? placeholder: these both should generate the same sql.

def self.search(search, page = 1 )
  wildcard_search = "%#{search}%"

  where("name ILIKE ? OR postal_code LIKE ?", wildcard_search, wildcard_search)
    .page(page)
    .per_page(5)
end

NOTE: using ILIKE for the name - postgres case insensitive version of LIKE