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REFACTOR: Reduce dependency on the post stream in TopicView.

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This will allow us to drop the post stream from the payload for
mega-topics. On smaller topics, the extra query is fast because
of an existing index.
This commit is contained in:
Guo Xiang Tan 2018-07-10 15:42:48 +08:00
parent 59950b0f95
commit 21f333654c
2 changed files with 43 additions and 58 deletions
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5
db/migrate/20180710075119_add_index_topic_id_sort_order_on_posts.rb Normal file
View File

@ -0,0 +1,5 @@
class AddIndexTopicIdSortOrderOnPosts < ActiveRecord::Migration[5.2]
def change
add_index :posts, [:topic_id, :sort_order], order: { sort_order: :asc }
end
end

96
lib/topic_view.rb
View File

@ -234,8 +234,38 @@ class TopicView
# Filter to all posts near a particular post number
def filter_posts_near(post_number)
min_idx, max_idx = get_minmax_ids(post_number)
filter_posts_in_range(min_idx, max_idx)
posts_before = (@limit.to_f / 4).floor
posts_before = 1 if posts_before.zero?
sort_order_sql = <<~SQL
(
SELECT posts.sort_order
FROM posts
WHERE posts.post_number = #{post_number.to_i}
AND posts.topic_id = #{@topic.id.to_i}
LIMIT 1
)
SQL
before_post_ids = @filtered_posts.order(sort_order: :desc)
.where("posts.sort_order < #{sort_order_sql}",)
.limit(posts_before)
.pluck(:id)
post_ids = before_post_ids + @filtered_posts.order(sort_order: :asc)
.where("posts.sort_order >= #{sort_order_sql}")
.limit(@limit - before_post_ids.length)
.pluck(:id)
if post_ids.length < @limit
post_ids = post_ids + @filtered_posts.order(sort_order: :desc)
.where("posts.sort_order < #{sort_order_sql}")
.offset(before_post_ids.length)
.limit(@limit - post_ids.length)
.pluck(:id)
end
filter_posts_by_ids(post_ids)
end
def filter_posts_paged(page)
@ -245,9 +275,12 @@ class TopicView
# Sometimes we don't care about the OP, for example when embedding comments
min = 1 if min == 0 && @exclude_first
max = (min + @limit) - 1
filter_posts_in_range(min, max)
@posts = filter_posts_by_ids(
@filtered_posts.order(:sort_order)
.offset(min)
.limit(@limit)
.pluck(:id)
)
end
def filter_best(max, opts = {})
@ -456,19 +489,6 @@ class TopicView
@posts
end
def filter_posts_in_range(min, max)
post_count = (filtered_post_ids.length - 1)
max = [max, post_count].min
return @posts = Post.none if min > max
min = [[min, max].min, 0].max
@posts = filter_posts_by_ids(filtered_post_ids[min..max])
@posts
end
def find_topic(topic_or_topic_id)
if topic_or_topic_id.is_a?(Topic)
topic_or_topic_id
@ -547,46 +567,6 @@ class TopicView
end
end
def get_minmax_ids(post_number)
# Find the closest number we have
closest_index = closest_post_to(post_number)
return nil if closest_index.nil?
# Make sure to get at least one post before, even with rounding
posts_before = (@limit.to_f / 4).floor
posts_before = 1 if posts_before.zero?
min_idx = closest_index - posts_before
min_idx = 0 if min_idx < 0
max_idx = min_idx + (@limit - 1)
# Get a full page even if at the end
ensure_full_page(min_idx, max_idx)
end
def ensure_full_page(min, max)
upper_limit = (filtered_post_ids.length - 1)
if max >= upper_limit
return (upper_limit - @limit) + 1, upper_limit
else
return min, max
end
end
def closest_post_to(post_number)
# happy path
closest_post_id = filtered_post_id(post_number)
if closest_post_id.blank?
# less happy path, missing post
closest_post_id = @filtered_posts.order("@(post_number - #{post_number})").limit(1).pluck(:id).first
end
return nil if closest_post_id.blank?
filtered_post_ids.index(closest_post_id) || filtered_post_ids[0]
end
MEGA_TOPIC_POSTS_COUNT = 10000
def is_mega_topic?