ArangoDB AQL:更新嵌入式阵列中的单个对象 [英] ArangoDB AQL: Update single object in embedded array

问题描述

我正在尝试使用AQL更新嵌入式数组中json文档上的属性.如何使用下面的AQL更新家庭"类型地址的地址栏"?

I am trying to update the attribute on a json document in an embedded array using AQL. How do i update the "addressline" for "home" type address using AQL below?

{
name: "test",
address: [
      {"addressline": "1234 superway", type:"home"}, 
      {"addressline": "5678 superway", type:"work"}
     ]
}

到目前为止的AQL尝试

for u in users
   for a in u.address
     FILTER a.type='home'
       UPDATE u WITH {<What goes here to update addressline?>} in users

谢谢您的帮助.

关于， 安詹

推荐答案

为此，我们必须使用临时变量.我们将在其中收集子列表并对其进行更改.我们选择一个简单的布尔过滤条件，以使查询更易于理解.

To do this we have to work with temporary variables. We will collect the sublist in there and alter it. We choose a simple boolean filter condition to make the query better comprehensible.

首先让我们创建一个带有样本的集合:

First lets create a collection with a sample:

database = db._create('complexCollection')
database.save({ 
  "topLevelAttribute" : "a", 
  "subList" : [ 
    { 
      "attributeToAlter" : "oldValue", 
      "filterByMe" : true 
    }, 
    { 
      "attributeToAlter" : "moreOldValues", 
      "filterByMe" : true 
    }, 
    { 
      "attributeToAlter" : "unchangedValue", 
      "filterByMe" : false 
    } 
  ] 
})

在此处保留 subList 在 alteredList 上的查询，以便以后进行更新:

Heres the Query which keeps the subList on alteredList to update it later:

FOR document in complexCollection
  LET alteredList = (
    FOR element IN document.subList 
       LET newItem = (! element.filterByMe ?
                      element :
                      MERGE(element, { attributeToAlter: "shiny New Value" }))
       RETURN newItem)
  UPDATE document WITH { subList:  alteredList } IN complexCollection

查询现在可以使用了:

db.complexCollection.toArray()
[ 
  { 
    "_id" : "complexCollection/392671569467", 
    "_key" : "392671569467", 
    "_rev" : "392799430203", 
    "topLevelAttribute" : "a", 
    "subList" : [ 
      { 
        "filterByMe" : true, 
        "attributeToAlter" : "shiny New Value" 
      }, 
      { 
        "filterByMe" : true, 
        "attributeToAlter" : "shiny New Value" 
      }, 
      { 
        "filterByMe" : false, 
        "attributeToAlter" : "unchangedValue" 
      } 
    ] 
  } 
]

此查询可能很快就会成为性能瓶颈，因为它会修改集合中的所有文档，无论值是否更改.因此，如果我们确实更改文档的值，我们只希望对文档进行 UPDATE .因此，我们使用第二个 FOR 来测试 subList 是否将被更改:

This query will probably be soonish a performance bottleneck, since it modifies all documents in the collection regardless whether the values change or not. Therefore we want to only UPDATE the documents if we really change their value. Therefore we employ a second FOR to test whether subList will be altered or not:

FOR document in complexCollection
  LET willUpdateDocument = (
    FOR element IN document.subList 
      FILTER element.filterByMe LIMIT 1 RETURN 1)

  FILTER LENGTH(willUpdateDocument) > 0

  LET alteredList = (
    FOR element IN document.subList 
       LET newItem = (! element.filterByMe ?
                      element :
                      MERGE(element, { attributeToAlter: "shiny New Value" }))
       RETURN newItem)

  UPDATE document WITH { subList:  alteredList } IN complexCollection

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