Highly concurrent mall system built on go-zero

https://github.com/zhoushuguang/lebron/blob/13ddeceee4f58459711f2f45302990ec5149913a/apps/product/rpc/internal/logic/productlistlogic.go#L124 请问此处传l.ctx更合适还是context.Background()更合适呢

https://github.com/zhoushuguang/lebron/blob/faf0719a58af6667ac1d413cb2096b69b768a1c6/sql/mall.sql#L107 1.字段按照其他表统一为没有下划线格式 2.id增加AUTO_INCREMENT属性

CREATE TABLE orderitem ( id bigint(20) unsigned NOT NULL AUTO_INCREMENT COMMENT '订单子表id', orderid varchar(64) NOT NULL DEFAULT '' COMMENT '订单id', userid bigint(20) UNSIGNED NOT NULL DEFAULT 0 COMMENT '用户id', proid bigint(20) UNSIGNED NOT NULL DEFAULT 0 COMMENT '商品id', proname varchar(100) NOT NULL DEFAULT '' COMMENT '商品名称', proimage varchar(500) NOT NULL DEFAULT '' COMMENT '商品图片地址', currentunitprice decimal(20, 2) NOT NULL DEFAULT 0 COMMENT '生成订单时的商品单价，单位是元,保留两位小数', quantity int(10) NOT NULL DEFAULT 0 COMMENT '商品数量', totalprice decimal(20, 2) NOT NULL DEFAULT 0 COMMENT '商品总价,单位是元,保留两位小数', create_time timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间', update_time timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间', PRIMARY KEY (id), KEY ix_orderid (orderid), KEY ix_userid (userid), KEY ix_proid (proid) ) ENGINE = InnoDB DEFAULT CHARSET = utf8mb4 COMMENT ='订单明细表';

go-zero微服务实战系列（五、缓存代码怎么写）里面的 ProductListRequest 结构为什么会有 ProductId

message ProductListRequest {
  int32 category_id = 1;
  int64 cursor = 2;
  int32 ps = 3;
  int64 product_id = 4;
}

请问这个 ProductId 的作用是什么?