Question

在rails中，我首先使用以下配置为activerecord。

config.active_record.default_timezone = :utc

现在，我想使用本地时区，因此我将其更改为：

config.active_record.default_timezone = :local

问题是，我需要将日期/日期时间列中的所有现有数据转移到本地时区。实现这一目标的最佳方法是什么？

<小时/> <子> 为什么我必须这样做是因为我必须在本地时区进行聚合，例如：group =＆gt; 'DATE（created_at）'，GROUP BY DATE（created_at）将基于UTC，但我希望在本地时区聚合一天。

我知道如何编写迁移文件来迁移某个日期时间列。但是有很多这样的专栏，所以我正在寻求更好的解决方案。

Answer 1

我的第一个建议是强烈建议你不要这样做。你正在打开一个受伤的世界。那就是说，这就是你想要的：

class ShootMyFutureSelfInTheFootMigration
  def up
    Walrus.find_each do |walrus|
      married_at_utc = walrus.married_at
      walrus.update_column(:married_at, married_at_utc.in_time_zone)
    end
  end

  def down
    Walrus.find_each do |walrus|
      married_at_local = walrus.married_at
      walrus.update_column(:married_at, married_at_local.utc)
    end
  end
end

您可以将首选时区传入DateTime＃in_time_zone，如下所示：

central_time_zone = ActiveSupport::TimeZone.new("Central Time (US & Canada)")
walrus.update_column(:married_at, married_at_utc.in_time_zone(central_time_zone))

或者你可以离开它，Rails将使用你当前的时区。请注意，这不是您所在的位置，而是您的服务器所在的位置。因此，如果您在冰岛和上海有用户，但您的服务器位于加利福尼亚州，则每个“本地”时区都将是美国太平洋时间。

Answer 2

这很危险，但这是我在迁移中所做的事情：

class MigrateDateTimesFromUTCToLocal < ActiveRecord::Migration

  def self.up
    # Eager load the application, in order to find all the models
    # Check your application.rb's load_paths is minimal and doesn't do anything adverse
    Rails.application.eager_load!

    # Now all the models are loaded. Let's loop through them
    # But first, Rails can have multiple models inheriting the same table
    # Let's get the unique tables
    uniq_models = ActiveRecord::Base.models.uniq_by{ |model| model.table_name }

    begin
      # Now let's loop
      uniq_models.each do |model|
        # Since we may be in the middle of many migrations,
        # Let's refresh the latest schema for that model
        model.reset_column_information

        # Filter only the date/time columns
        datetime_columns = model.columns.select{ |column| [ :datetime, :date, :time].include? column.type }

        # Process them
        # Remember *not* to loop through model.all.each, or something like that
        # Use plain SQL, since the migrations for many columns in that model may not have run yet
        datetime_columns.each do |column|
          execute <<-SQL
            UPDATE #{model.table_name} SET #{column.name} = /* DB-specific date/time conversion */
          SQL
        end

      rescue
        # Probably time to think about your rescue strategy
        # If you have tested the code properly in Test/Staging environments
        # Then it should run fine in Production
        # So if an exception happens, better re-throw it and handle it manually
      end

    end
  end
end

Answer 3

您必须更改数据库中的数据吗？您可以改为在当地时区显示日期。这有用吗：Convert UTC to local time in Rails 3

Answer 4

像很多其他人说的那样，你可能不想这样做。

您可以在分组之前将时间转换为其他区域，所有这些都在数据库中。例如，使用postgres，转换为Mountain Standard Time：

SELECT COUNT(id), DATE(created_at AT TIME ZONE 'MST') AS created_at_in_mst
FROM users GROUP BY created_at_in_mst;

更改活动记录的default_timezone

4 个答案: