discourse/app/services/sidebar_site_settings_backf...

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# frozen_string_literal: true
# A service class that backfills the changes to the default sidebar categories and tags site settings.
#
# When a category/tag is removed from the site settings, the `SidebarSectionLink` records associated with the category/tag
# are deleted.
#
# When a category/tag is added to the site settings, a `SidebarSectionLink` record for the associated category/tag are
# created for all users that do not already have a `SidebarSectionLink` record for the category/tag.
class SidebarSiteSettingsBackfiller
def initialize(setting_name, previous_value:, new_value:)
@setting_name = setting_name
@linkable_klass, previous_ids, new_ids =
case setting_name
when "default_sidebar_categories"
[
Category,
previous_value.split("|"),
new_value.split("|")
]
when "default_sidebar_tags"
klass = Tag
[
klass,
klass.where(name: previous_value.split("|")).pluck(:id),
klass.where(name: new_value.split("|")).pluck(:id)
]
else
raise 'Invalid setting_name'
end
@added_ids = new_ids - previous_ids
@removed_ids = previous_ids - new_ids
end
def backfill!
DistributedMutex.synchronize("backfill_sidebar_site_settings_#{@setting_name}") do
SidebarSectionLink.where(linkable_type: @linkable_klass.to_s, linkable_id: @removed_ids).delete_all
User.real.where(staged: false).select(:id).find_in_batches do |users|
rows = []
users.each do |user|
@added_ids.each do |linkable_id|
rows << { user_id: user[:id], linkable_type: @linkable_klass.to_s, linkable_id: linkable_id }
end
end
SidebarSectionLink.insert_all(rows) if rows.present?
end
end
end
def number_of_users_to_backfill
select_statements = []
if @removed_ids.present?
select_statements.push(<<~SQL)
SELECT
sidebar_section_links.user_id
FROM sidebar_section_links
WHERE sidebar_section_links.linkable_type = '#{@linkable_klass.to_s}'
AND sidebar_section_links.linkable_id IN (#{@removed_ids.join(",")})
SQL
end
if @added_ids.present?
# Returns the ids of users that will receive the new additions by excluding the users that already have the additions
# Note that we want to avoid doing a left outer join against the "sidebar_section_links" table as PG will end up having
# to do a full table join for both tables first which is less efficient and can be slow on large sites.
select_statements.push(<<~SQL)
SELECT
users.id
FROM users
WHERE users.id NOT IN (
SELECT
sidebar_section_links.user_id
FROM sidebar_section_links
WHERE sidebar_section_links.linkable_type = '#{@linkable_klass.to_s}'
AND sidebar_section_links.linkable_id IN (#{@added_ids.join(",")})
) AND users.id > 0 AND NOT users.staged
SQL
end
DB.query_single(<<~SQL)[0]
SELECT
COUNT(*)
FROM (#{select_statements.join("\nUNION DISTINCT\n")}) AS user_ids
SQL
end
end