多次使用位置`$`运算符来更新嵌套数组 [英] Multiple use of the positional `$` operator to update nested arrays

问题描述

这个问题与这个问题密切相关，我将考虑给出的建议关于NoSQL上下文中的模式设计，但我很好奇这一点:

This question is closely related to this one and I will consider the advice given with respect to schema design in a NoSQL context, yet I'm curious to understand this:

假设您具有以下文档:

    _id : 2      abcd
    name : 2     unittest.com
    paths : 4    
        0 : 3    
            path : 2     home
            queries : 4      
                0 : 3    
                    name : 2     query1
                    url : 2      www.unittest.com/home?query1
                    requests: 4

                1 : 3    
                    name : 2     query2
                    url : 2      www.unittest.com/home?query2
                    requests: 4

基本上，我想知道

1. ，如果可以使用MongoDB的位置$运算符(

1. if it is possible to use MongoDB's positional $ operator (details) multiple times, or put differently, in update scenarios that involve array/document structures with a "degree of nestedness" greater than 1:

{ <update operator>: { "paths.$.queries.$.requests" : value } }(不起作用)

可以使用$ 一次而不是仅"用于顶级数组，并且必须对更高级别"的数组使用显式索引:

instead of "only" be able to use $ once for a top-level array and being bound to use explicit indexes for arrays on "higher levels":

{ <update operator>: { "paths.$.queries.0.requests" : value } })(作品)

如果可能的话，相应的R语法是什么样子.

if possible at all, how the corresponding R syntax would look like.

下面您将找到一个可复制的示例.我试图尽可能简洁.

Below you'll find a reproducible example. I tried to be as concise as possible.

require("rmongodb")
db  <- "__unittest" 
ns  <- paste(db, "hosts", sep=".")
# CONNCETION OBJECT
con <- mongo.create(db=db)
# ENSURE EMPTY DB
mongo.remove(mongo=con, ns=ns)

示例文档

q <- list("_id"="abcd")
b <- list("_id"="abcd", name="unittest.com")
mongo.insert(mongo=con, ns=ns, b=b)
q <- list("_id"="abcd")
b <- list("$push"=list(paths=list(path="home")))
mongo.update(mongo=con, ns, criteria=q, objNew=b)
q <- list("_id"="abcd", paths.path="home")
b <- list("$push"=list("paths.$.queries"=list(
    name="query1", url="www.unittest.com/home?query1")))
mongo.update(mongo=con, ns, criteria=q, objNew=b)
b <- list("$push"=list("paths.$.queries"=list(
    name="query2", url="www.unittest.com/home?query2")))
mongo.update(mongo=con, ns, criteria=q, objNew=b)

使用显式位置索引更新嵌套数组(有效)

这可行，但是它涉及第二级数组queries的 explicit 索引(嵌套在数组paths的子文档元素中):

Update of nested arrays with explicit position index (works)

This works, but it involves an explicit index for the second-level array queries (nested in a subdoc element of array paths):

q <- list("_id"="abcd", paths.path="home", paths.queries.name="query1")
b <- list("$push"=list("paths.$.queries.0.requests"=list(time="2013-02-13")))
> mongo.bson.from.list(b)
    $push : 3    
        paths.$.queries.0.requests : 3   
            time : 2     2013-02-13

mongo.update(mongo=con, ns, criteria=q, objNew=b)
res <- mongo.find.one(mongo=con, ns=ns, query=q)
> res
    _id : 2      abcd
    name : 2     unittest.com
    paths : 4    
        0 : 3    
            path : 2     home
            queries : 4      
                0 : 3    
                    name : 2     query1
                    requests : 4     
                        0 : 3    
                            time : 2     2013-02-13


                    url : 2      www.unittest.com/home?query1

                1 : 3    
                    name : 2     query2
                    url : 2      www.unittest.com/home?query2

使用位置$索引更新嵌套数组(无效)

现在，我想用位置$运算符替换显式的0，就像我为了让服务器找到所需的数组paths(paths.$.queries)的子文档元素一样.

Update of nested arrays with positional $ indexes (doesn't work)

Now, I'd like to substitute the explicit 0 with the positional $ operator just like I did in order to have the server find the desired subdoc element of array paths (paths.$.queries).

AFAIU 文档，这应该是至关重要的事情是指定一个正确的"查询选择器:

AFAIU the documentation, this should work as the crucial thing is to specify a "correct" query selector:

位置$运算符与update()方法一起使用时，用作更新查询选择器的第一个匹配项的占位符:

The positional $ operator, when used with the update() method and acts as a placeholder for the first match of the update query selector:

我想我指定了一个查询选择器，它确实找到了正确的嵌套元素(由于paths.queries.name="query1"部分):

I think I specified a query selector that does find the correct nested element (due to the paths.queries.name="query1" part):

q <- list("_id"="abcd", paths.path="home", paths.queries.name="query1")

我猜翻译为普通MongoDB"语法，查询选择器看起来像这样

I guess translated to "plain MongoDB" syntax, the query selector looks somewhat like this

{ _id: abcd, paths.path: home, paths.queries.name: query1 }

对我来说似乎是一个有效的查询选择器.实际上，它确实符合所需的元素/文档:

which seems like a valid query selector to me. In fact it does match the desired element/doc:

> !is.null(mongo.find.one(mongo=con, ns=ns, query=q))
[1] TRUE

我的想法是，如果它可以在顶层使用，为什么它也不能在更高级别使用(只要查询选择器指向正确的嵌套组件)?

My thought was that if it works on the top-level, why shouldn't it work for higher levels as well (as long as the query selector points to the right nested components)?

但是，服务器似乎不喜欢$的嵌套或多次使用:

However, the server doesn't seem to like a nested or multiple use of $:

b <- list("$push"=list("paths.$.queries.$.requests"=list(time="2013-02-14")))
> mongo.bson.from.list(b)
    $push : 3    
        paths.$.queries.$.requests : 3   
            time : 2     2013-02-14

> mongo.update(mongo=con, ns, criteria=q, objNew=b)
[1] FALSE

我不确定它是否不起作用，因为MongoDB不支持此功能，或者我没有正确使用R语法.

I'm not sure if it doesn't work because MongoDB doesn't support this or if I didn't get the R syntax right.

推荐答案

位置运算符仅支持一个级别的深度，并且仅支持第一个匹配元素.

The positional operator only supports one level deep and only the first matching element.

这里有一个针对您想要的行为的JIRA可跟踪: https://jira.mongodb.org/browse /SERVER-831

There is a JIRA trackable for the sort of behaviour you want here: https://jira.mongodb.org/browse/SERVER-831

我不确定是否可以进行多场比赛，但我相信这是由于工作方式的动态变化所致.

I am unsure if it will allow for more than one match but I believe it will due to the dynamics of how it will need to work.

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