如何添加到 Cypher 地图中的现有值？

Question

我想用现有 'Amount' 值加上新的 'Amount' 值的总和来替换地图（文字）中 'Amount' 键的值，例如'type' 和 'Price' 匹配。到目前为止我的结构是：

WITH [{type:1, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]},
{type:2, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]},
{type:3, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]}] as ExistingOrders,
{type:2, Order:{Price:11,Amount:50}} as NewOrder

（我正在尝试将其发送到:)

RETURN [{type:1, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]} , {type:2, Orders:[{Price:10,Amount:100},{Price:11,Amount:250},{Price:12,Amount:300}]}, {type:3, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]}] 作为 CombinedOrders

如果不存在 NewOrder.type 和 NewOrder.Price 那么显然应该插入新记录而不是将它们加在一起。

抱歉，这可能真的很简单，但我还不是很擅长。

谢谢

编辑：

我应该补充一点，我已经能够为这样一个更简单的地图结构工作：

WITH [{type:1, Amount:100},{type:2, Amount:200},{type:3, Amount:300}] as ExistingOrders,
{type:2, Amount:50} as NewValue
RETURN reduce(map=filter(p in ExistingOrders where not p.type=NewValue.type),x in [(filter(p2 in ExistingOrders where p2.type=NewValue.type)[0])]|CASE x WHEN null THEN NewValue ELSE {type:x.type,Amount:x.Amount+NewValue.Amount} END+map) as CombinedOrders

但我觉得我正在努力，因为第一个示例中的订单[数组]。

Answer 1

您的问题有两个部分 - 一个有简单的答案，第二个部分没有意义。先说简单的吧！

据我所知，您似乎在询问如何将新地图连接到地图集合。那么，如何在数组中添加一个新项。就像这个简单的例子一样使用 +：

return [{item:1}, {item:2}] + [{item:3}];

请注意，我们在最后添加的单个项目不是地图，而是只有一个项目的集合。

所以对于您的查询：

RETURN [
    {type:1, Orders:[{Price:10,Amount:100},
                     {Price:11,Amount:200},
                     {Price:12,Amount:300}]},
    {type:2, Orders:[{Price:10,Amount:100},
                     {Price:11,Amount:**250**},
                     {Price:12,Amount:300}]}] 
    + 
    [{type:3, Orders:[{Price:10,Amount:100},
                     {Price:11,Amount:200},{Price:12,Amount:300}]}] 
as **CombinedOrders**

应该可以解决问题。

或者你可以做得更干净一些，像这样：

WITH [{type:1, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]},
{type:2, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]},
{type:3, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]}] as ExistingOrders,
{type:2, Order:{Price:11,Amount:50}} as NewOrder
RETURN ExistingOrders + [NewOrder];

现在看没有意义的部分。在您的示例中，您似乎想要修改集合内的地图。但是您那里有两个 {type:2} 映射，并且您希望将它们合并成一个结果 {type:3} 映射在您要求的输出中。如果您需要消除映射条目的冲突并更改映射条目应该是什么，那么对于这种查询，cypher 可能不是您的最佳选择。

Answer 2

我相信您只是想更新 ExistingOrders 中适当 Amount 的值。

以下查询是合法的Cypher，应该正常工作：

WITH ExistingOrders, NewOrder, [x IN ExistingOrders WHERE x.type = NewOrder.type | x.Orders] AS eo
FOREACH (y IN eo |
  SET y.Amount = y.Amount + CASE WHEN y.Price = NewOrder.Order.Price THEN NewOrder.Order.Amount ELSE 0 END
)

但是，上面的查询产生了一个（有点）有趣的 ThisShouldNotHappenError 错误消息：

Developer: Stefan claims that: This should be a node or a relationship

该消息试图表达的意思是（以迟钝的方式）您没有以正确的方式使用 neo4j 数据库。您的属性太复杂了，应该分成节点和关系。

所以，我将提出一个能够做到这一点的数据模型。以下是如何创建表示与 ExistingOrders 相同数据的节点和关系：

CREATE (t1:Type {id:1}), (t2:Type {id:2}), (t3:Type {id:3}), 
  (t1)-[:HAS_ORDER]->(:Order {Price:10,Amount:100}),
  (t1)-[:HAS_ORDER]->(:Order {Price:11,Amount:200}),
  (t1)-[:HAS_ORDER]->(:Order {Price:12,Amount:300}),
  (t2)-[:HAS_ORDER]->(:Order {Price:10,Amount:100}),
  (t2)-[:HAS_ORDER]->(:Order {Price:11,Amount:200}),
  (t2)-[:HAS_ORDER]->(:Order {Price:12,Amount:300}),
  (t3)-[:HAS_ORDER]->(:Order {Price:10,Amount:100}),
  (t3)-[:HAS_ORDER]->(:Order {Price:11,Amount:200}),
  (t3)-[:HAS_ORDER]->(:Order {Price:12,Amount:300});

这是一个将更新正确 Amount:

的查询

WITH {type:2, Order:{Price:11,Amount:50}} as NewOrder
MATCH (t:Type)-[:HAS_ORDER]->(o:Order)
WHERE t.id = NewOrder.type AND o.Price = NewOrder.Order.Price
SET o.Amount = o.Amount + NewOrder.Order.Amount
RETURN t.id, o.Price, o.Amount;

Answer 3

我想通了：

WITH [{type:1, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},Price:12,Amount:300}]},{type:2, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]},{type:3, Orders:[{Price:10,Amount:100},{Price:11,Amount:200},{Price:12,Amount:300}]}] as ExistingOrders,{type:2, Orders:[{Price:11,Amount:50}]} as NewOrder
RETURN 
reduce(map=filter(p in ExistingOrders where not p.type=NewOrder.type),
x in [(filter(p2 in ExistingOrders where p2.type=NewOrder.type)[0])]|
CASE x 
WHEN null THEN NewOrder 
ELSE {type:x.type, Orders:[
    reduce(map2=filter(p3 in x.Orders where not (p3.Price=(NewOrder.Orders[0]).Price)),
    x2 in [filter(p4 in x.Orders where p4.Price=(NewOrder.Orders[0]).Price)[0]]|
    CASE x2 
    WHEN null THEN NewOrder.Orders[0] 
    ELSE {Price:x2.Price, Amount:x2.Amount+(NewOrder.Orders[0]).Amount} 
    END+map2 )]} END+map) as CombinedOrders

...使用嵌套的 Reduce 函数。

因此，首先它将没有匹配 type 的订单列表与这些订单的列表（实际上只有一个）与匹配type。对于后者 ExistingOrders（type 与 NewOrder 匹配），它在嵌套 reduce 函数中与 Price 做类似的事情，并结合不匹配的 Prices 匹配 Prices，在后一种情况下添加 Amount。

如何添加到 Cypher 地图中的现有值？

How to add to an existing value in a map in Cypher?

neo4j

cypher