The doc says to use the tag_list accessor as normal, but even with a cahced_tag_list column present, a query is being performed to get an object's tags.
Example:
posts/show
<%= @post.tag_list %>
=> SELECT tags.* FROM tags INNER JOIN taggings ON tags.id = taggings.tag_id WHERE ((taggings.taggable_id = 12345) AND (taggings.taggable_type = 'Post'))
I would expect it to return the cached tag list instead. Caching does work as expected when editing an object, and no query is performed.
I cant see an issue here, there are tests that cover this scenario. Are you sure the cache column is named correctly and is populated. Post.caching_tag_list? should return true, does it?