Change hashtag trends to be stored in the database instead of redis

app/controllers/api/v1/trends/tags_controller.rb

@@ -27,7 +27,9 @@ class Api::V1::Trends::TagsController < Api::BaseController
   end
 
   def tags_from_trends
-    Trends.tags.query.allowed
+    scope = Trends.tags.query.allowed.in_locale(content_locale)
+    scope = scope.filtered_for(current_account) if user_signed_in?
+    scope
   end
 
   def next_path

app/models/tag.rb

@@ -32,6 +32,8 @@ class Tag < ApplicationRecord
   has_many :featured_tags, dependent: :destroy, inverse_of: :tag
   has_many :followers, through: :passive_relationships, source: :account
 
+  has_one :trend, class_name: 'TagTrend', inverse_of: :tag, dependent: :destroy
+
   HASHTAG_SEPARATORS = "_\u00B7\u30FB\u200c"
   HASHTAG_FIRST_SEQUENCE_CHUNK_ONE = "[[:word:]_][[:word:]#{HASHTAG_SEPARATORS}]*[[:alpha:]#{HASHTAG_SEPARATORS}]"
   HASHTAG_FIRST_SEQUENCE_CHUNK_TWO = "[[:word:]#{HASHTAG_SEPARATORS}]*[[:word:]_]"
@@ -101,8 +103,12 @@ class Tag < ApplicationRecord
     max_score_at && max_score_at >= Trends.tags.options[:max_score_cooldown].ago && max_score_at < 1.day.ago
   end
 
-  def history
+  def history(language = nil)
+    if language.nil?
       @history ||= Trends::History.new('tags', id)
+    else
+      Trends::History.new("tags:#{language}", id)
+    end
   end
 
   class << self

app/models/tag_trend.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: tag_trends
+#
+#  id       :bigint(8)        not null, primary key
+#  tag_id   :bigint(8)        not null
+#  score    :float            default(0.0), not null
+#  rank     :integer          default(0), not null
+#  allowed  :boolean          default(FALSE), not null
+#  language :string
+#
+class TagTrend < ApplicationRecord
+  include RankedTrend
+
+  belongs_to :tag
+
+  scope :allowed, -> { where(allowed: true) }
+  scope :not_allowed, -> { where(allowed: false) }
+end

app/models/trends/base.rb

@@ -37,18 +37,6 @@ class Trends::Base
     Trends::Query.new(key_prefix, klass)
   end
 
-  def score(id, locale: nil)
-    redis.zscore([key_prefix, 'all', locale].compact.join(':'), id) || 0
-  end
-
-  def rank(id, locale: nil)
-    redis.zrevrank([key_prefix, 'allowed', locale].compact.join(':'), id)
-  end
-
-  def currently_trending_ids(allowed, limit)
-    redis.zrevrange(allowed ? "#{key_prefix}:allowed" : "#{key_prefix}:all", 0, limit.positive? ? limit - 1 : limit).map(&:to_i)
-  end
-
   protected
 
   def key_prefix
@@ -64,42 +52,9 @@ class Trends::Base
     redis.expire(used_key(at_time), 1.day.seconds)
   end
 
-  def score_at_rank(rank)
-    redis.zrevrange("#{key_prefix}:allowed", 0, rank, with_scores: true).last&.last || 0
-  end
-
-  def replace_items(suffix, items)
-    tmp_prefix    = "#{key_prefix}:tmp:#{SecureRandom.alphanumeric(6)}#{suffix}"
-    allowed_items = filter_for_allowed_items(items)
-
-    redis.pipelined do |pipeline|
-      items.each { |item| pipeline.zadd("#{tmp_prefix}:all", item[:score], item[:item].id) }
-      allowed_items.each { |item| pipeline.zadd("#{tmp_prefix}:allowed", item[:score], item[:item].id) }
-
-      rename_set(pipeline, "#{tmp_prefix}:all", "#{key_prefix}:all#{suffix}", items)
-      rename_set(pipeline, "#{tmp_prefix}:allowed", "#{key_prefix}:allowed#{suffix}", allowed_items)
-    end
-  end
-
-  def filter_for_allowed_items(items)
-    raise NotImplementedError
-  end
-
   private
 
   def used_key(at_time)
     "#{key_prefix}:used:#{at_time.beginning_of_day.to_i}"
   end
-
-  def rename_set(pipeline, from_key, to_key, set_items)
-    if set_items.empty?
-      pipeline.del(to_key)
-    else
-      pipeline.rename(from_key, to_key)
-    end
-  end
-
-  def skip_review?
-    Setting.trendable_by_default
-  end
 end

app/models/trends/query.rb

@@ -1,15 +1,13 @@
 # frozen_string_literal: true
 
 class Trends::Query
-  include Redisable
   include Enumerable
 
-  attr_reader :prefix, :klass, :loaded
+  attr_reader :klass, :loaded
 
   alias loaded? loaded
 
-  def initialize(prefix, klass)
-    @prefix  = prefix
+  def initialize(_prefix, klass)
     @klass   = klass
     @records = []
     @loaded  = false
@@ -68,22 +66,11 @@ class Trends::Query
   alias to_a to_ary
 
   def to_arel
-    if ids_for_key.empty?
-      klass.none
-    else
-      scope = klass.joins(sanitized_join_sql).reorder('x.ordering')
-      scope = scope.offset(@offset) if @offset.present?
-      scope = scope.limit(@limit) if @limit.present?
-      scope
-    end
+    raise NotImplementedError
   end
 
   private
 
-  def key
-    [@prefix, @allowed ? 'allowed' : 'all', @locale].compact.join(':')
-  end
-
   def load
     unless loaded?
       @records = perform_queries
@@ -93,29 +80,7 @@ class Trends::Query
     self
   end
 
-  def ids_for_key
-    @ids_for_key ||= redis.zrevrange(key, 0, -1).map(&:to_i)
-  end
-
-  def sanitized_join_sql
-    ActiveRecord::Base.sanitize_sql_array(join_sql_array)
-  end
-
-  def join_sql_array
-    [join_sql_query, ids_for_key]
-  end
-
-  def join_sql_query
-    <<~SQL.squish
-      JOIN unnest(array[?]) WITH ordinality AS x (id, ordering) ON #{klass.table_name}.id = x.id
-    SQL
-  end
-
   def perform_queries
-    apply_scopes(to_arel).to_a
-  end
-
-  def apply_scopes(scope)
-    scope
+    to_arel.to_a
   end
 end

app/models/trends/tags.rb

@@ -11,34 +11,93 @@ class Trends::Tags < Trends::Base
     decay_threshold: 1,
   }
 
+  class Query < Trends::Query
+    def filtered_for!(account)
+      @account = account
+      self
+    end
+
+    def filtered_for(account)
+      clone.filtered_for!(account)
+    end
+
+    def to_arel
+      scope = Tag.joins(:trend).reorder(language_order_clause.desc, score: :desc)
+      scope = scope.merge(TagTrend.allowed) if @allowed
+      scope = scope.offset(@offset) if @offset.present?
+      scope = scope.limit(@limit) if @limit.present?
+      scope
+    end
+
+    private
+
+    def language_order_clause
+      Arel::Nodes::Case.new.when(TagTrend.arel_table[:language].in(preferred_languages)).then(1).else(0)
+    end
+
+    def preferred_languages
+      if @account&.chosen_languages.present?
+        @account.chosen_languages
+      else
+        @locale
+      end
+    end
+  end
+
   def register(status, at_time = Time.now.utc)
     return unless !status.reblog? && status.public_visibility? && !status.account.silenced?
 
     status.tags.each do |tag|
-      add(tag, status.account_id, at_time) if tag.usable?
+      add(tag, status.account_id, status.language, at_time) if tag.usable?
     end
   end
 
-  def add(tag, account_id, at_time = Time.now.utc)
+  def add(tag, account_id, language, at_time = Time.now.utc)
+    # This history is used for display purposes
     tag.history.add(account_id, at_time)
-    record_used_id(tag.id, at_time)
+
+    # This history is used for calculating the score
+    tag.history(language).add(account_id, at_time)
+
+    # We need to save the language along with the hashtag so we know which languages to calculate for later
+    record_used_id("#{tag.id}:#{language}", at_time)
+  end
+
+  def query
+    Query.new(key_prefix, klass)
   end
 
   def refresh(at_time = Time.now.utc)
-    tags = Tag.where(id: (recently_used_ids(at_time) + currently_trending_ids(false, -1)).uniq)
+    # First, recalculate scores for links that were trending previously. We split the queries
+    # to avoid having to load all of the IDs into Ruby just to send them back into Postgres
+    Tag.where(id: TagTrend.select(:tag_id)).find_in_batches(batch_size: BATCH_SIZE) do |tags|
       calculate_scores(tags, at_time)
     end
 
+    # Then, calculate scores for links that were used today. There are potentially some
+    # duplicate items here that we might process one more time, but that should be fine
+    Tag.where(id: recently_used_ids(at_time).map { |str| str.split(':').first }.uniq).find_in_batches(batch_size: BATCH_SIZE) do |tags|
+      calculate_scores(tags, at_time)
+    end
+
+    # Now that all trends have up-to-date scores, and all the ones below the threshold have
+    # been removed, we can recalculate their positions
+    TagTrend.recalculate_ordered_rank
+  end
+
   def request_review
-    tags = Tag.where(id: currently_trending_ids(false, -1))
+    score_at_threshold  = TagTrend.allowed.by_rank.ranked_below(options[:review_threshold]).first&.score || 0
+    preview_card_trends = TagTrend.not_allowed.includes(:tag)
 
-    tags.filter_map do |tag|
-      next unless would_be_trending?(tag.id) && !tag.trendable? && tag.requires_review_notification?
+    preview_card_trends.filter_map do |trend|
+      tag = trend.tag
 
+      if trend.score > score_at_threshold && !tag.trendable? && tag.requires_review_notification?
         tag.touch(:requested_review_at)
         tag
       end
     end
+  end
 
   protected
 
@@ -53,9 +112,7 @@ class Trends::Tags < Trends::Base
   private
 
   def calculate_scores(tags, at_time)
-    items = []
-
-    tags.each do |tag|
+    items = tags.map do |tag|
       expected  = tag.history.get(at_time - 1.day).accounts.to_f
       expected  = 1.0 if expected.zero?
       observed  = tag.history.get(at_time).accounts.to_f
@@ -79,19 +136,13 @@ class Trends::Tags < Trends::Base
 
       decaying_score = max_score * (0.5**((at_time.to_f - max_time.to_f) / options[:max_score_halflife].to_f))
 
-      next unless decaying_score >= options[:decay_threshold]
-
-      items << { score: decaying_score, item: tag }
+      [decaying_score, tag]
     end
 
-    replace_items('', items)
-  end
+    to_insert = items.filter { |(score, _)| score >= options[:decay_threshold] }
+    to_delete = items.filter { |(score, _)| score < options[:decay_threshold] }
 
-  def filter_for_allowed_items(items)
-    items.select { |item| item[:item].trendable? }
-  end
-
-  def would_be_trending?(id)
-    score(id) > score_at_rank(options[:review_threshold] - 1)
+    TagTrend.upsert_all(to_insert.map { |(score, tag)| { tag_id: tag.id, score: score, languages: [], allowed: tag.trendable? || false } }, unique_by: :tag_id) if to_insert.any?
+    TagTrend.where(tag_id: to_delete.map { |(_, tag)| tag.id }).delete_all if to_delete.any?
   end
 end

db/migrate/20241111141355_create_tag_trends.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class CreateTagTrends < ActiveRecord::Migration[7.2]
+  def change
+    create_table :tag_trends do |t| # rubocop:disable Rails/CreateTableWithTimestamps
+      t.references :tag, null: false, foreign_key: { on_delete: :cascade }, index: false
+      t.float :score, null: false, default: 0
+      t.integer :rank, null: false, default: 0
+      t.boolean :allowed, null: false, default: false
+      t.string :language
+    end
+
+    add_index :tag_trends, [:tag_id, :language], unique: true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2024_11_04_082851) do
+ActiveRecord::Schema[7.1].define(version: 2024_11_11_141355) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -1080,6 +1080,15 @@ ActiveRecord::Schema[7.2].define(version: 2024_11_04_082851) do
     t.index ["tag_id"], name: "index_tag_follows_on_tag_id"
   end
 
+  create_table "tag_trends", force: :cascade do |t|
+    t.bigint "tag_id", null: false
+    t.float "score", default: 0.0, null: false
+    t.integer "rank", default: 0, null: false
+    t.boolean "allowed", default: false, null: false
+    t.string "language"
+    t.index ["tag_id", "language"], name: "index_tag_trends_on_tag_id_and_language", unique: true
+  end
+
   create_table "tags", force: :cascade do |t|
     t.string "name", default: "", null: false
     t.datetime "created_at", precision: nil, null: false
@@ -1343,6 +1352,7 @@ ActiveRecord::Schema[7.2].define(version: 2024_11_04_082851) do
   add_foreign_key "statuses_tags", "tags", name: "fk_3081861e21", on_delete: :cascade
   add_foreign_key "tag_follows", "accounts", on_delete: :cascade
   add_foreign_key "tag_follows", "tags", on_delete: :cascade
+  add_foreign_key "tag_trends", "tags", on_delete: :cascade
   add_foreign_key "tombstones", "accounts", on_delete: :cascade
   add_foreign_key "user_invite_requests", "users", on_delete: :cascade
   add_foreign_key "users", "accounts", name: "fk_50500f500d", on_delete: :cascade

spec/fabricators/tag_trend_fabricator.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+Fabricator(:tag_trend) do
+  tag_id   ''
+  score    1.5
+  rank     1
+  allowed  false
+  language 'MyString'
+end

spec/models/tag_trend_spec.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe TagTrend do
+  pending "add some examples to (or delete) #{__FILE__}"
+end