如何使用gocql动态添加查询参数？

如何解决如何使用gocql动态添加查询参数？

在一个函数（Golang，Gocql，Cassandra）中基于过滤器输入（vendor_id，customer_id，order_status_id ...或同时包含所有非空字段）编写查询的最佳方式是什么？我不想在每种情况下都编写新功能，例如下面的仅按customerID过滤的功能：

func (repo *orderRepo) FindByCustomerId(req *pb.FindRequest) (*pb.OrdersResponse,error) {
    offset := req.GetOffset()
    limit := req.GetLimit()
    customerID := req.GetCustomerId()
    //vendorID := req.GetVendorId()
    //orderStatusID := req.GetOrderStatusId()
    var (
        orders []*pb.Order
        count  int32
    )
    if err := repo.session.Query(`SELECT count(1) FROM orders WHERE customer_id = ?`,customerID).
        Scan(&count); err != nil {
        return nil,err
    }
    if offset < count {
        query := repo.session.Query(`SELECT
            id,customer_id,customer_name,vendor_id,toJSON(items),paid_at,created_at,order_status_id
        FROM orders WHERE customer_id = ?`,customerID)
        defer query.Release()
        var ps []byte
        iter := query.PageState(ps).PageSize(int(offset % limit)).Iter()
        ps = iter.PageState()
        page := offset / limit
        var i int32
        for i = 0; i < page; i++ {
            iter = query.PageState(ps).PageSize(int(limit)).Iter()
            ps = iter.PageState()
        }
        iter = query.PageState(ps).PageSize(int(limit)).Iter()
        rows := iter.Scanner()
        for rows.Next() {
            var (
                order                pb.Order
                createdAt            time.Time
                paidAt               time.Time
                itemsJSON            []byte
            )
            if err := rows.Scan(
                &order.Id,&order.CustomerId,&order.CustomerName,&order.VendorId,&itemsJSON,&paidAt,&createdAt,&order.OrderStatusId,); err != nil {
                return nil,err
            }
            if err := json.Unmarshal(itemsJSON,&order.Items); err != nil {
                return nil,err
            }
            order.PaidAt = paidAt.String()
            order.CreatedAt = createdAt.String()
            orders = append(orders,&order)
        }

        if err := iter.Close(); err != nil {
            return nil,err
        }
    }

    return &pb.OrdersResponse{
        Orders: orders,Count:  count,},nil
}

我需要为上述查询动态添加参数

解决方法

这是我三天后提出的自己的问题的解决方案：）我认为这对其他人有帮助

func (repo *orderRepo) Find(req *pb.FindRequest) (*pb.OrdersResponse,error) {
    offset := req.GetOffset()
    limit := req.GetLimit()
    vendorID := req.GetVendorId()
    customerID := req.GetCustomerId()
    orderStatusID := req.GetOrderStatusId()

    var (
        orders []*pb.Order
        count  int32
    )

    var filter string
    var values []interface{}
    if len(vendorID) > 0 {
        if len(filter) > 0 {
            filter = filter + " AND vendor_id = ?"
        } else {
            filter = " WHERE vendor_id = ?"
        }
        values = append(values,vendorID)
    }
    if len(customerID) > 0 {
        if len(filter) > 0 {
            filter = filter + " AND customer_id = ?"
        } else {
            filter = " WHERE customer_id = ?"
        }
        values = append(values,customerID)

    }
    if len(orderStatusID) > 0 {
        if len(filter) > 0 {
            filter = filter + " AND order_status_id = ?"
        } else {
            filter = " WHERE order_status_id = ?"
        }
        values = append(values,orderStatusID)
    }

    fmt.Println(filter)

    if err := repo.session.Query(`SELECT count(1) FROM orders`+filter,values...).
        Scan(&count); err != nil {
        return nil,err
    }

    if offset < count {
        query := repo.session.Query(`SELECT
        id,customer_id,customer_name,vendor_id,toJSON(items),paid_at,created_at,order_status_id
        FROM orders`+filter,values...)
        defer query.Release()

        var ps []byte
        iter := query.PageState(ps).PageSize(int(offset % limit)).Iter()
        ps = iter.PageState()

        page := offset / limit
        var i int32
        for i = 0; i < page; i++ {
            iter = query.PageState(ps).PageSize(int(limit)).Iter()
            ps = iter.PageState()
        }
        iter = query.PageState(ps).PageSize(int(limit)).Iter()

        rows := iter.Scanner()
        for rows.Next() {
            var (
                order                pb.Order
                createdAt            time.Time
                paidAt               time.Time
                itemsJSON            []byte
            )
            if err := rows.Scan(
                &order.Id,&order.CustomerId,&order.CustomerName,&order.VendorId,&itemsJSON,&paidAt,&createdAt,&order.OrderStatusId,); err != nil {
                return nil,err
            }
            if err := json.Unmarshal(itemsJSON,&order.Items); err != nil {
                return nil,err
            }
            order.PaidAt = paidAt.String()
            order.CreatedAt = createdAt.String()
            orders = append(orders,&order)
        }

        if err := iter.Close(); err != nil {
            return nil,err
        }
    }

    return &pb.OrdersResponse{
        Orders: orders,Count:  count,},nil
}