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PERF: Speed up home page unread+new query 

restructure query so it avoids ORs

It appears postgres is picking suboptimal indexes if too many ORs exist
despite how trivial the condition is.

This bypasses conditional in the query and evals them upfront.

On meta for my user this made a 10x perf difference.

This boils down to either having `OR u.admin` or not having `OR u.admin` in
the query.
This commit is contained in:
Sam Saffron 2019-04-05 15:25:19 +11:00
parent 5b837f620b
commit 81a1bafe54
1 changed files with 53 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

73
app/models/topic_tracking_state.rb
View File

@ -168,11 +168,24 @@ class TopicTrackingState
#
# This code needs to be VERY efficient as it is triggered via the message bus and may steal
# cycles from usual requests
#
#
sql = report_raw_sql(topic_id: topic_id, skip_unread: true, skip_order: true, staff: user.staff?)
sql = report_raw_sql(
topic_id: topic_id,
skip_unread: true,
skip_order: true,
staff: user.staff?,
admin: user.admin?
)
sql << "\nUNION ALL\n\n"
sql << report_raw_sql(topic_id: topic_id, skip_new: true, skip_order: true, staff: user.staff?, filter_old_unread: true)
sql << report_raw_sql(
topic_id: topic_id,
skip_new: true,
skip_order: true,
staff: user.staff?,
filter_old_unread: true,
admin: user.admin?
)
DB.query(
sql,
@ -183,9 +196,10 @@ class TopicTrackingState
end
def self.report_raw_sql(opts = nil)
opts ||= {}
unread =
if opts && opts[:skip_unread]
if opts[:skip_unread]
"1=0"
else
TopicQuery
@ -196,30 +210,54 @@ class TopicTrackingState
end
filter_old_unread =
if opts && opts[:filter_old_unread]
if opts[:filter_old_unread]
" topics.updated_at >= us.first_unread_at AND "
else
""
end
new =
if opts && opts[:skip_new]
if opts[:skip_new]
"1=0"
else
TopicQuery.new_filter(Topic, "xxx").where_clause.send(:predicates).join(" AND ").gsub!("'xxx'", treat_as_new_topic_clause) +
" AND topics.created_at > :min_new_topic_date"
end
select = (opts && opts[:select]) || "
select = (opts[:select]) || "
u.id AS user_id,
topics.id AS topic_id,
topics.created_at,
#{opts && opts[:staff] ? "highest_staff_post_number highest_post_number" : "highest_post_number"},
#{opts[:staff] ? "highest_staff_post_number highest_post_number" : "highest_post_number"},
last_read_post_number,
c.id AS category_id,
tu.notification_level"
sql = +<<SQL
category_filter =
if opts[:admin]
""
else
append = "OR u.admin" if !opts.key?(:admin)
<<~SQL
(
NOT c.read_restricted #{append} OR category_id IN (
SELECT c2.id FROM categories c2
JOIN category_groups cg ON cg.category_id = c2.id
JOIN group_users gu ON gu.user_id = :user_id AND cg.group_id = gu.group_id
WHERE c2.read_restricted )
) AND
SQL
end
visibility_filter =
if opts[:staff]
""
else
append = "OR u.admin OR u.moderator" if !opts.key?(:staff)
"(topics.visible #{append}) AND"
end
sql = +<<~SQL
SELECT #{select}
FROM topics
JOIN users u on u.id = :user_id
@ -231,15 +269,10 @@ class TopicTrackingState
#{filter_old_unread}
topics.archetype <> 'private_message' AND
((#{unread}) OR (#{new})) AND
(topics.visible OR u.admin OR u.moderator) AND
#{visibility_filter}
topics.deleted_at IS NULL AND
( NOT c.read_restricted OR u.admin OR category_id IN (
SELECT c2.id FROM categories c2
JOIN category_groups cg ON cg.category_id = c2.id
JOIN group_users gu ON gu.user_id = :user_id AND cg.group_id = gu.group_id
WHERE c2.read_restricted )
)
AND NOT EXISTS( SELECT 1 FROM category_users cu
#{category_filter}
NOT EXISTS( SELECT 1 FROM category_users cu
WHERE last_read_post_number IS NULL AND
cu.user_id = :user_id AND
cu.category_id = topics.category_id AND
@ -247,11 +280,11 @@ class TopicTrackingState
SQL
if opts && opts[:topic_id]
if opts[:topic_id]
sql << " AND topics.id = :topic_id"
end
unless opts && opts[:skip_order]
unless opts[:skip_order]
sql << " ORDER BY topics.bumped_at DESC"
end