Module: ActiveRecord::CollectionCacheKey

Included in:
Base
Defined in:
lib/active_record/collection_cache_key.rb

Instance Method Summary collapse

Instance Method Details

#collection_cache_key(collection = all, timestamp_column = :updated_at) ⇒ Object

:nodoc:



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# File 'lib/active_record/collection_cache_key.rb', line 3

def collection_cache_key(collection = all, timestamp_column = :updated_at) # :nodoc:
  query_signature = Digest::MD5.hexdigest(collection.to_sql)
  key = "#{collection.model_name.cache_key}/query-#{query_signature}"

  if collection.loaded?
    size = collection.size
    if size > 0
      timestamp = collection.max_by(&timestamp_column)._read_attribute(timestamp_column)
    end
  else
    column_type = type_for_attribute(timestamp_column.to_s)
    column = "#{connection.quote_table_name(collection.table_name)}.#{connection.quote_column_name(timestamp_column)}"
    select_values = "COUNT(*) AS #{connection.quote_column_name("size")}, MAX(%s) AS timestamp"

    if collection.limit_value || collection.offset_value
      query = collection.spawn
      query.select_values = [column]
      subquery_alias = "subquery_for_cache_key"
      subquery_column = "#{subquery_alias}.#{timestamp_column}"
      subquery = query.arel.as(subquery_alias)
      arel = Arel::SelectManager.new(query.engine).project(select_values % subquery_column).from(subquery)
    else
      query = collection.unscope(:order)
      query.select_values = [select_values % column]
      arel = query.arel
    end

    result = connection.select_one(arel, nil, query.bound_attributes)

    if result.blank?
      size = 0
      timestamp = nil
    else
      size = result["size"]
      timestamp = column_type.deserialize(result["timestamp"])
    end

  end

  if timestamp
    "#{key}-#{size}-#{timestamp.utc.to_s(cache_timestamp_format)}"
  else
    "#{key}-#{size}"
  end
end