ruby-on-rails - 在 Hash 中保存错误排序后的 activerecord-postgres-hstore

Question

用Hstore存储为Hash Table，保存后Hash顺序错误

class Service < ActiveRecord::Base
  serialize :properties, ActiveRecord::Coders::Hstore
end

service = Service.new
service.properties = { "aaa" => 1, "zz" => 2, "cc" => 3, "d" => 4 }
#=> { "aaa" => 1, "zz" => 2, "cc" => 3, "d" => 4 }
service.save
reload!
service = Service.find(:id)
service.properties
#=> { "d" => "4", "cc" => "3", "zz" => 2, "aaa" => 1 }
Bug::: wrong ordering after save

是不是因为序列化之后是按Tree排序的。任何想法或任何人以前都遇到过这个问题？提前致谢。

Answer 1

来自fine PostgreSQL manual :

F.16. hstore
[...]
This module implements the hstore data type for storing sets of key/value pairs within a single PostgreSQL value.
[...]
The order of the pairs is not significant (and may not be reproduced on output).

因此 PostgreSQL 的 hstore 类型是一组无序的键/值对，不保证键/值对的任何特定顺序。一旦您的 Ruby 哈希转换为 hstore，排序就会丢失。

如果您需要维护哈希中的顺序，则必须使用不同的序列化格式。