Remove the category constraint option from RelatedTagCalculator.calculate_from_posts.
It slows things down and isn't used.
This method is used to calculate the related tags sidebar during
searches for single metatags. Using Tag.category_for in the inner loop
caused a memcache call on every iteration. At 100 posts per page and
20-30 tags per post, this led to up to 2000-3000 total memcache calls,
which significantly slowed pageloads.
8404064854