Comments have three states: visible, hidden, and invisible. Visible
comments are always shown. Hidden comments are not shown until the user
clicks 'Show all comments'. Invisible comments are never shown to the
user. Deleted comments are treated as hidden for moderators and
invisible for normal users. Thresholded comments are treated as hidden
for all users.
Bug: if all the comments on a post were deleted then the deleted
comments wouldn't be visible to moderators.
This was because we assumed that if `last_commented_at` was nil it meant
that the post had no comments, but this was wrong. `last_commented_at`
only counts undeleted comments. It's reset to nil if all the commnets
have been deleted.
Certain parts of comment rendering triggered sql queries that we didn't
really need to do. Rework things to avoid this.
* Preload comment creators in order to display commenter names with link_to_user.
* Preload comment votes in order to display "undo vote" links. Only preload
votes for members since anonymous users can't vote and don't have "undo
vote" links.
* Rework various conditionals to do the filtering in Ruby so that we
avoid issuing any extra queries in sql.
* Avoid issuing any queries at all when the post doesn't have any
comments (when last_commented_at is blank).
Changes:
* Drop Users.id_to_name.
* Don't cache Users.name_to_id.
* Replace calls to name_to_id with find_by_name when possible.
* Don't autodefine creator_name in belongs_to_creator.
* Don't autodefine updater_name in belongs_to_updater.
* Instead manually define creator_name / updater_name only on models that need
to return these fields in the api.
id_to_name was cached to reduce the impact of N+1 query patterns in
certain places, especially in api responses that return creator_name /
updater_name fields. But it still meant we were doing N calls to
memcache. Using `includes` to prefetch users avoids this N+1 pattern.
name_to_id had no need be cached, it was never used in any performance-
sensitive contexts.
Avoiding caching also avoids the need to keep these caches consistent.
Refactor tag_list_html, split_tag_list_html, and inline_tag_list_html to
take the `show_extra_links` and `current_query` options explicitly,
rather than implicitly relying on CurrentUser or taking `params[:tags]`
from the template.
* Restore behavior of thresholded comments being greyed out (lost in 6fa0ae2cf).
* Set the `below-threshold` class for thresholded comments in the html instead of in javascript.
* Remove `include_below_threshold` param; it was always true when clicking "Show all comments".
Mark the edit form, new comment form, and unvote links as hidden in
html, instead of showing them by default then hiding them later in
Javascript. This eliminates flickering on page load.
Eager load post comments' creators and updaters. Fixes an N+1 queries
problem when rendering commenter names at:
views/comments/partials/show/_comment.html.erb:6
views/comments/partials/show/_comment.html.erb:20
while rendering /posts/:id pages.
* Add 'post as moderator' option to comment form. This creates a so-called sticky comment.
* Downvotes have no effect on stickied comments; they're always visible, regardless of comment thresholds.
* Only mods may sticky comments.
* Mods may sticky comments by other users.
