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

db/migrate/20250318024953_copy_solved_topic_custom_field_to_discourse_solved_topics.rb

@@ -1,38 +1,53 @@
 # 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
-      INSERT INTO discourse_solved_topics (
-        topic_id,
-        answer_post_id,
-        topic_timer_id,
-        accepter_user_id,
-        created_at,
-        updated_at
-      ) SELECT DISTINCT
-        tc.topic_id,
-        CAST(tc.value AS INTEGER),
-        CAST(tc2.value AS INTEGER),
-        ua.acting_user_id,
-        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'
-      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}
-    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,
+          topic_timer_id,
+          accepter_user_id,
+          created_at,
+          updated_at
+        )
+        SELECT DISTINCT ON (tc.topic_id)
+          tc.topic_id,
+          CAST(tc.value AS INTEGER),
+          CAST(tc2.value AS INTEGER),
+          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'
+        LEFT JOIN user_actions ua
+          ON ua.target_topic_id = tc.topic_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