Module: AridCache::CacheProxy::Utilities

Extended by:
Utilities
Included in:
AridCache, Utilities
Defined in:
lib/arid_cache/cache_proxy/utilities.rb

Instance Method Summary collapse

Instance Method Details

#collection_klass(collection) ⇒ Object

Infer the class of the objects in a collection. The collection could be empty. If the collection is a relation or proxy reflection we can get the class from it.

Return the class or nil if no class can be inferred.



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# File 'lib/arid_cache/cache_proxy/utilities.rb', line 72

def collection_klass(collection)
  if collection.respond_to?(:proxy_reflection)
    collection.proxy_reflection.klass
  elsif defined?(::ActiveRecord::Relation) && collection.is_a?(::ActiveRecord::Relation)
    collection.klass
  elsif collection.respond_to?(:first) && collection.first
    collection.first.class
  end
end

#find_all_by_id(klass, ids, find_opts = {}) ⇒ Object

Find and return records of the given klass which have id in ids. find_opts is a hash of options which are passed to find. If no order option is given, the ordering of the ids is preserved. No query is performed if ids is empty.



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# File 'lib/arid_cache/cache_proxy/utilities.rb', line 43

def find_all_by_id(klass, ids, find_opts={})
  return ids if ids.empty?
  find_opts = Options.new(find_opts.merge(:result_klass => klass)).opts_for_find(ids)
  if AridCache.framework.active_record?(3)
    option_map = {
      :conditions => :where,
      :include => :includes
    }
    query = find_opts.inject(klass.scoped) do |scope, pair|
      key, value = pair
      key = option_map[key] || key
      scope.send(key, pair[1])
    end
    query = query.scoped.where(Utilities.namespaced_column(:id, klass) + ' in (?)', ids)
    # Fix http://breakthebit.org/post/3487560245/rails-3-arel-count-size-length-weirdness
    query.class_eval do
      alias_method :size, :length
      alias_method :count, :length
    end
    query
  else
    klass.find_all_by_id(ids, find_opts)
  end
end

#namespaced_column(column, klass = nil) ⇒ Object

Return the column name quoted and namespaced by the table name, if the klass responds to table_name. Otherwise just return the column unchanged.



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# File 'lib/arid_cache/cache_proxy/utilities.rb', line 26

def namespaced_column(column, klass=nil)
  if klass.respond_to?(:table_name)
    ::ActiveRecord::Base.connection.quote_table_name(klass.table_name) + '.' + column.to_s
  else
    column.to_s
  end
end

#object_class(object) ⇒ Object

Return the object’s class or the object if it is a class.



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# File 'lib/arid_cache/cache_proxy/utilities.rb', line 35

def object_class(object)
  object.is_a?(Class) ? object : object.class
end

#order_by(ids, klass = nil) ⇒ Object

Generate an ORDER BY clause that preserves the ordering of the ids in ids.

The method we use depends on the database adapter because only MySQL supports the ORDER BY FIELD() function. For other databases we use a CASE statement.



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# File 'lib/arid_cache/cache_proxy/utilities.rb', line 11

def order_by(ids, klass=nil)
  column = namespaced_column(:id, klass)
  if ids.empty?
    nil
  elsif ::ActiveRecord::Base.is_mysql_adapter?
    "FIELD(#{column},#{ids.join(',')})"
  else
    order = ''
    ids.each_index { |i| order << "WHEN #{column}=#{ids[i]} THEN #{i+1} " }
    "CASE " + order + " END"
  end
end