Model在循环内执行自增/自减操作后的save问题

模拟一个扣库存动作

 for ($i = 0; $i < 10; $i++) {
            $info = (new MerchantGoods())->where('id', 1)->findOrEmpty();
            $info->dec('stock_qty', 1)->save();
        }

上面的写法执行后无论库存数是都是,最终均会被设置成1
跟踪后发现最后一次执行的update语句为UPDATE b_merchant_goods SET stock_qty = '1' WHERE id = '1'

改写成一下方式则符合预期

  for ($i = 0; $i < 10; $i++) {
            $info = (new MerchantGoods())->where('id', 1)->findOrEmpty();
            $info->save([
                'stock_qty' => Db::Raw('stock_qty -1'),
            ]);
        }

Start by running the issue's loop reproduction and compare the generated update for dec('stock_qty', 1)->save() with the Db::Raw alternative. No source file or test is named; trace the dec and save entry points, then add coverage showing repeated iterations preserve each decrement instead of resetting the value.