Batch migration due to sites having > 200k rows of solved

db/migrate/20250318024953_copy_solved_topic_custom_field_to_discourse_solved_topics.rb

@@ -1,16 +1,22 @@
 # frozen_string_literal: true
 #
 class CopySolvedTopicCustomFieldToDiscourseSolvedTopics < ActiveRecord::Migration[7.2]
+  disable_ddl_transaction!
+
+  BATCH_SIZE = 5000
+
   def up
     create_table :discourse_solved_topics do |t|
       t.integer :topic_id, null: false
       t.integer :answer_post_id, null: false
-      t.integer :accepter_user_id
+      t.integer :accepter_user_id, null: false
       t.integer :topic_timer_id
       t.timestamps
     end
 
-    execute <<-SQL
+    last_id = 0
+    loop do
+      rows = DB.query(<<~SQL, last_id: last_id, batch_size: BATCH_SIZE)
         INSERT INTO discourse_solved_topics (
           topic_id,
           answer_post_id,
@@ -18,21 +24,30 @@ class CopySolvedTopicCustomFieldToDiscourseSolvedTopics < ActiveRecord::Migratio
           accepter_user_id,
           created_at,
           updated_at
-      ) SELECT DISTINCT
+        )
+        SELECT DISTINCT ON (tc.topic_id)
           tc.topic_id,
           CAST(tc.value AS INTEGER),
           CAST(tc2.value AS INTEGER),
-        ua.acting_user_id,
+          COALESCE(ua.acting_user_id, -1),
           tc.created_at,
           tc.updated_at
         FROM topic_custom_fields tc
         LEFT JOIN topic_custom_fields tc2
-      ON tc2.topic_id = tc.topic_id AND tc2.name = 'solved_auto_close_topic_timer_id'
+          ON tc2.topic_id = tc.topic_id
+          AND tc2.name = 'solved_auto_close_topic_timer_id'
         LEFT JOIN user_actions ua
           ON ua.target_topic_id = tc.topic_id
-      WHERE tc.name = 'accepted_answer_post_id'
           AND ua.action_type = #{UserAction::SOLVED}
+        WHERE tc.name = 'accepted_answer_post_id'
+          AND tc.id > :last_id
+        ORDER BY tc.topic_id, ua.created_at DESC
+        LIMIT :batch_size
       SQL
+
+      break if rows.length == 0
+      last_id += BATCH_SIZE
+    end
   end
 
   def down