PERF: .find_each instead of .find to save us from memory allocation peaks

also Fix embeddings rake task for new db structure

lib/modules/embeddings/strategies/truncation.rb

@@ -52,7 +52,7 @@ module DiscourseAi
           end
           t << "\n\n"
 
-          topic.posts.each do |post|
+          topic.posts.find_each do |post|
             t << post.raw
             break if @tokenizer.size(t) >= @max_length
             t << "\n\n"

lib/tasks/modules/embeddings/database.rake

@@ -1,33 +1,21 @@
 # frozen_string_literal: true
 
-desc "Creates tables to store embeddings"
-task "ai:embeddings:create_table" => [:environment] do
-  DiscourseAi::Database::Connection.db.exec(<<~SQL)
-    CREATE EXTENSION IF NOT EXISTS vector;
-  SQL
-
-  DiscourseAi::Embeddings::Model.enabled_models.each do |model|
-    DiscourseAi::Database::Connection.db.exec(<<~SQL)
-        CREATE TABLE IF NOT EXISTS topic_embeddings_#{model.name.underscore} (
-          topic_id bigint PRIMARY KEY,
-          embedding vector(#{model.dimensions})
-        );
-      SQL
-  end
-end
-
 desc "Backfill embeddings for all topics"
 task "ai:embeddings:backfill", [:start_topic] => [:environment] do |_, args|
   public_categories = Category.where(read_restricted: false).pluck(:id)
-  topic_embeddings = DiscourseAi::Embeddings::Topic.new
+  manager = DiscourseAi::Embeddings::Manager.new(Topic.first)
   Topic
-    .where("id >= ?", args[:start_topic] || 0)
+    .joins(
+      "LEFT JOIN #{manager.topic_embeddings_table} ON #{manager.topic_embeddings_table}.topic_id = topics.id",
+    )
+    .where("#{manager.topic_embeddings_table}.topic_id IS NULL")
+    .where("topics.id >= ?", args[:start_topic].to_i || 0)
     .where("category_id IN (?)", public_categories)
     .where(deleted_at: nil)
-    .order(id: :asc)
+    .order("topics.id ASC")
     .find_each do |t|
       print "."
-      topic_embeddings.generate_and_store_embeddings_for(t)
+      DiscourseAi::Embeddings::Manager.new(t).generate!
     end
 end
 
@@ -35,24 +23,30 @@ desc "Creates indexes for embeddings"
 task "ai:embeddings:index", [:work_mem] => [:environment] do |_, args|
   # Using extension maintainer's recommendation for ivfflat indexes
   # Results are not as good as without indexes, but it's much faster
-  # Disk usage is ~1x the size of the table, so this double table total size
+  # Disk usage is ~1x the size of the table, so this doubles table total size
   count = Topic.count
   lists = count < 1_000_000 ? count / 1000 : Math.sqrt(count).to_i
   probes = count < 1_000_000 ? lists / 10 : Math.sqrt(lists).to_i
 
-  DiscourseAi::Database::Connection.db.exec("SET work_mem TO '#{args[:work_mem] || "1GB"}';")
-  DiscourseAi::Embeddings::Model.enabled_models.each do |model|
-    DiscourseAi::Database::Connection.db.exec(<<~SQL)
+  manager = DiscourseAi::Embeddings::Manager.new(Topic.first)
+  table = manager.topic_embeddings_table
+  index = "#{table}_search"
+
+  DB.exec("SET work_mem TO '#{args[:work_mem] || "1GB"}';")
+  DB.exec(<<~SQL)
+    DROP INDEX IF EXISTS #{index};
     CREATE INDEX IF NOT EXISTS
-        topic_embeddings_#{model.name.underscore}_search
+      #{index}
     ON
-        topic_embeddings_#{model.name.underscore}
+      #{table}
     USING
-        ivfflat (embedding #{model.pg_index})
+      ivfflat (embeddings #{manager.model.pg_index_type})
     WITH
-        (lists = #{lists});
+      (lists = #{lists})
+    WHERE
+      model_version = #{manager.model.version} AND
+      strategy_version = #{manager.strategy.version};
   SQL
-  end
-  DiscourseAi::Database::Connection.db.exec("RESET work_mem;")
-  DiscourseAi::Database::Connection.db.exec("SET ivfflat.probes = #{probes};")
+  DB.exec("RESET work_mem;")
+  DB.exec("SET ivfflat.probes = #{probes};")
 end