Tolan/backend/migrations/backfill_user_chatbot_slot_placements_scene_snapshots.sql

-- 根据 shop_items.render_image_name 回填槽位快照（已有装备过家具的用户）
-- 前提：已执行 add_shop_items_render_image_name.sql
-- 仅当商品配置了 render_image_name 且与当前 snapshot 不一致时更新为场景图

UPDATE `user_chatbot_slot_placements` usp
INNER JOIN `shop_items` si ON si.id = usp.item_id
SET usp.`image_name_snapshot` = NULLIF(TRIM(si.`render_image_name`), ''),
    usp.`updated_at` = NOW()
WHERE usp.`item_id` IS NOT NULL
  AND NULLIF(TRIM(si.`render_image_name`), '') IS NOT NULL
  AND usp.`image_name_snapshot` <> NULLIF(TRIM(si.`render_image_name`), '');