访问 ruby 计数器缓存
我正在尝试使用acts_as_taggable_on_steroids 的分支作为学习练习。我正在查看的版本做了一些我不明白的事情来计算标签计数。所以我想我应该使用 PORC（Plain Old Rails Counters）做一个版本：
class Tagging < ActiveRecord::Base #:nodoc:
belongs_to :tag, :counter_cache => "tagging_counter_cache"
...
我认为当我访问 tag.taggings.count 时， tagging_counter_cache 被透明地访问，但显然不是？我真的必须显式访问 tag.tagging_counter_cache 吗？
>> tag.taggings.count
SQL (0.7ms) SELECT count(*) AS count_all FROM `taggings` WHERE (`taggings`.tag_id = 16)
尺寸相同。
如果是这样的话那就很酷了，但只是想检查一下。
I'm playing around with a fork of acts_as_taggable_on_steroids as a learning exercise. The version I'm looking at does some stuff I don't understand to calculate Tag counts. So I thought I'd do a version using PORC (Plain Old Rails Counters):
class Tagging < ActiveRecord::Base #:nodoc:
belongs_to :tag, :counter_cache => "tagging_counter_cache"
...
I thought tagging_counter_cache was transparently accessed when I access tag.taggings.count but apparently not? Do I really have to access tag.tagging_counter_cache explicitly?
>> tag.taggings.count
SQL (0.7ms) SELECT count(*) AS count_all FROM `taggings` WHERE (`taggings`.tag_id = 16)
Same for size.
It's cool if that's the case but just wanted to check.
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对集合调用#size
将返回计数器缓存中的值。调用 #count
将始终强制 sql 调用来获取最新计数。
Calling #size on the collection
will return the value in the counter cache. Calling #count
will always force a sql call to get the latest count.
您是否在迁移中创建了关联列？它需要某个地方来存储缓存。
Did you create the associated column in your migration? It needs someplace to store the cache.