I am trying to update a value in the nested array but can't get it to work.
My object is like this
{
"_id": {
"$oid": "1"
},
"array1": [
{
"_id": "12",
"array2": [
{
"_id": "123",
"answeredBy": [], // need to push "success"
},
{
"_id": "124",
"answeredBy": [],
}
],
}
]
}
I need to push a value to "answeredBy" array.
In the below example, I tried pushing "success" string to the "answeredBy" array of the "123 _id" object but it does not work.
callback = function(err,value){
if(err){
res.send(err);
}else{
res.send(value);
}
};
conditions = {
"_id": 1,
"array1._id": 12,
"array2._id": 123
};
updates = {
$push: {
"array2.$.answeredBy": "success"
}
};
options = {
upsert: true
};
Model.update(conditions, updates, options, callback);
I found this link, but its answer only says I should use object like structure instead of array's. This cannot be applied in my situation. I really need my object to be nested in arrays
It would be great if you can help me out here. I've been spending hours to figure this out.
Thank you in advance!
General Scope and Explanation
There are a few things wrong with what you are doing here. Firstly your query conditions. You are referring to several _id values where you should not need to, and at least one of which is not on the top level.
In order to get into a "nested" value and also presuming that _id value is unique and would not appear in any other document, you query form should be like this:
Model.update(
{ "array1.array2._id": "123" },
{ "$push": { "array1.0.array2.$.answeredBy": "success" } },
function(err,numAffected) {
// something with the result in here
}
);
Now that would actually work, but really it is only a fluke that it does as there are very good reasons why it should not work for you.
The important reading is in the official documentation for the positional $ operator under the subject of "Nested Arrays". What this says is:
The positional $ operator cannot be used for queries which traverse more than one array, such as queries that traverse arrays nested within other arrays, because the replacement for the $ placeholder is a single value
Specifically what that means is the element that will be matched and returned in the positional placeholder is the value of the index from the first matching array. This means in your case the matching index on the "top" level array.
So if you look at the query notation as shown, we have "hardcoded" the first ( or 0 index ) position in the top level array, and it just so happens that the matching element within "array2" is also the zero index entry.
To demonstrate this you can change the matching _id value to "124" and the result will $push an new entry onto the element with _id "123" as they are both in the zero index entry of "array1" and that is the value returned to the placeholder.
So that is the general problem with nesting arrays. You could remove one of the levels and you would still be able to $push to the correct element in your "top" array, but there would still be multiple levels.
Try to avoid nesting arrays as you will run into update problems as is shown.
The general case is to "flatten" the things you "think" are "levels" and actually make theses "attributes" on the final detail items. For example, the "flattened" form of the structure in the question should be something like:
{
"answers": [
{ "by": "success", "type2": "123", "type1": "12" }
]
}
Or even when accepting the inner array is $push only, and never updated:
{
"array": [
{ "type1": "12", "type2": "123", "answeredBy": ["success"] },
{ "type1": "12", "type2": "124", "answeredBy": [] }
]
}
Which both lend themselves to atomic updates within the scope of the positional $ operator
MongoDB 3.6 and Above
From MongoDB 3.6 there are new features available to work with nested arrays. This uses the positional filtered $[<identifier>] syntax in order to match the specific elements and apply different conditions through arrayFilters in the update statement:
Model.update(
{
"_id": 1,
"array1": {
"$elemMatch": {
"_id": "12","array2._id": "123"
}
}
},
{
"$push": { "array1.$[outer].array2.$[inner].answeredBy": "success" }
},
{
"arrayFilters": [{ "outer._id": "12" },{ "inner._id": "123" }]
}
)
The "arrayFilters" as passed to the options for .update() or even
.updateOne(), .updateMany(), .findOneAndUpdate() or .bulkWrite() method specifies the conditions to match on the identifier given in the update statement. Any elements that match the condition given will be updated.
Because the structure is "nested", we actually use "multiple filters" as is specified with an "array" of filter definitions as shown. The marked "identifier" is used in matching against the positional filtered $[<identifier>] syntax actually used in the update block of the statement. In this case inner and outer are the identifiers used for each condition as specified with the nested chain.
This new expansion makes the update of nested array content possible, but it does not really help with the practicality of "querying" such data, so the same caveats apply as explained earlier.
You typically really "mean" to express as "attributes", even if your brain initially thinks "nesting", it's just usually a reaction to how you believe the "previous relational parts" come together. In reality you really need more denormalization.
Also see How to Update Multiple Array Elements in mongodb, since these new update operators actually match and update "multiple array elements" rather than just the first, which has been the previous action of positional updates.
NOTE Somewhat ironically, since this is specified in the "options" argument for .update() and like methods, the syntax is generally compatible with all recent release driver versions.
However this is not true of the mongo shell, since the way the method is implemented there ( "ironically for backward compatibility" ) the arrayFilters argument is not recognized and removed by an internal method that parses the options in order to deliver "backward compatibility" with prior MongoDB server versions and a "legacy" .update() API call syntax.
So if you want to use the command in the mongo shell or other "shell based" products ( notably Robo 3T ) you need a latest version from either the development branch or production release as of 3.6 or greater.
See also positional all $[] which also updates "multiple array elements" but without applying to specified conditions and applies to all elements in the array where that is the desired action.
I know this is a very old question, but I just struggled with this problem myself, and found, what I believe to be, a better answer.
A way to solve this problem is to use Sub-Documents. This is done by nesting schemas within your schemas
MainSchema = new mongoose.Schema({
array1: [Array1Schema]
})
Array1Schema = new mongoose.Schema({
array2: [Array2Schema]
})
Array2Schema = new mongoose.Schema({
answeredBy": [...]
})
This way the object will look like the one you show, but now each array are filled with sub-documents. This makes it possible to dot your way into the sub-document you want. Instead of using a .update you then use a .find or .findOne to get the document you want to update.
Main.findOne((
{
_id: 1
}
)
.exec(
function(err, result){
result.array1.id(12).array2.id(123).answeredBy.push('success')
result.save(function(err){
console.log(result)
});
}
)
Haven't used the .push() function this way myself, so the syntax might not be right, but I have used both .set() and .remove(), and both works perfectly fine.
Related
So I have a collection looking like this:
[
{"url":"website.com/test", "links":[ {"url": "www.something.fr/page.html","scoreDiff": 0.44} ], "justUpdated": true, "score": 0.91},
{"url":"domain.com/", "links":[], "justUpdated": true, "score": 0.81},
{"url":"www.something.fr/page.html", "links":[], "justUpdated": false, "score": 0.42},
]
The goal here is to get the third document, because in one of the documents where "justUpdated" equals true (the first one here), there is its url as a value in one of the "links" array elements.
To achieve that, I tried:
To find all the documents with "justUpdated" equals to true, then in NodeJS concatenate all the urls in their "links" arrays (let's call this array urlsOfInterest). And finally do another query to find all the documents where the url is in urlsOfInterest.
The problem is that it takes some time to do the first query then process the result and do the second query.
So I thought maybe I could do it all at once in an aggregate query. I use $group (with $cond to check if justUpdated equals true) to get all the arrays of "links" in one new variable named urlsOfInterest. For now this is an array of arrays of object so I then use $project with $reduce to have all these {url: "...", score: X} objects as one big array. Finally I use $project and $map to only have the url as the score value doesn't interest me here.
So I get an output looking like this:
_id:"urlsOfInterest",
urlsOfInterest: ["www.something.fr/page.html"]
Which is pretty great but I am stuck because now I just need to get the documents where url is in this variable named urlsOfInterest except I can't because all my documents have "disappeared" after the $group stage.
Please help me to find a way to perform this final query :) Or if this isn't the right way to do this, please point me in the right direction !
PS: the real goal here would be to update for all the documents where justUpdated equals true, every scoreDiff values in their links array. For our exemple, we do abs(0.91 - 0.42) = 0.49 so we replace our scoreDiff value of 0.44 by 0.49 (0.91 being the score of the document where justUpdated equals true and 0.42 the score of the document where url equals www.something.fr/page.html, explaining why I need to fetch this last document.) I don't believe there could be a way of doing all of this at once but if there is, please tell me !
You can use $lookup to get all matching documents in an array:
db.collection.aggregate([
{
"$match": {
"justUpdated": true
}
},
{
"$lookup": {
"from": "collection",
"localField": "links.url",
"foreignField": "url",
"as": "result"
}
},
{
"$match": {
"result": {
$gt: []
}
}
}
])
Then either $unwind and $replaceRoot the results array to get the documents as a cursor and do the math on the application level or do the calculations in the same pipeline, e.g. with $reduce
The "PS: the real goal" is not quite clear as it is based on a particular example but if you play a little bit with it in the playground I am sure you can calculate the numbers as per your requirements.
I need to do some additional filtering of the data I'm getting, so that I'm only getting the data that match certain criteria. I'm trying to find a combination of operators I can use to accomplish this via a functional programming approach. I'm thinking perhaps a combination of filter and reduce might work? Could I simply chain a combination of them together to get the result I'm looking for?
My data structure looks like this:
"data": [
{
"_id": "53545",
"services": [
{
"service": "service1",
"history": [
{
"_id": "6546",
"status": "stage1",
"completed": true
},
{
**"_id": "6547",
"status": "stage2",
"completed": false**
}
],
{
"service": "service2",
"history": [
{
"_id": "6743",
"status": "stage3",
"completed": false
},
{
"_id": "3742",
"status": "stage2",
"completed": true
}
]
},
{
"service": "service3",
"history": [
{
"_id": "6448",
"status": "stage4",
"completed": false
},
{
"_id": "4443",
"status": "stage1",
"completed": true
}
]
}
]
To be clear, here data, services and history are ALL arrays. And in the case of the above data, only one object within "history" should pass the tests, as there is only one object where "status:stage2" and "completed:false". BUT that means that, within the "data" array, this particular object, the one with the "_id": "53545" SHOULD pass, as the tests returned true for it. And ultimately, I'm wanting to return an array, from within the objects within the "data" array, that match like this one does.
Very specifically, in my case, there are always 3 services. Within each of those 3, there might be 1 or as many as 30 or more history objects. I need to look through all 3 "services", and find the history objects where the status is "stage2" and "completed:false". So this should return true if ANY of the three services have a history object with "status:stage2" and "completed:false".
I'm getting tripped up iterating over arrays within arrays.
I could get it directly in this manner:
let stage2Data = data.filter(data => data.services[0].history[1].status === 'stage2' && data.services[0].history[1].completed === false);
However, I obviously don't know what item number in these various arrays will contain the value I'm looking for. So what's the best way to tackle this? I suppose a series of for-of loops could work as well, but I'd like to use a more functional approach, and was thinking a combination of "filter" and "reduce", or perhaps "map" could work here. How would I only return the objects within the "data" array where ""status": "stage2" and "completed": false is true for at least one of the objects within the "history" array?
We've been going back and forth in the comments to try to get a valid data structure in your question. Let me give you a simple example of how you can make this much easier for everyone.
First, use the snippet button at the top of the editor box to create a snippet. It's the icon that looks like a typical "folded corner" document icon with <> inside it.
This will open up a popup box with places for HTML/CSS/JavaScript code. Ignore the HTML and CSS boxes and paste your data object into the JavaScript box.
Because it's not JavaScript "as is", wrap it inside an assignment statement to get a JavaScript variable that you can work with.
Then add a console.log statement at the end to display the data. Use the Run button to make sure the code actually parses and runs and displays the data correctly. Once you do that, it will be much easier for people to help you.
Here is a simplified example:
const input = {
"data": [
{
"one": "two"
},
{
"three": "four"
}
]
};
console.log( JSON.stringify( input, null, 4 ) );
Click the Run code snippet button above to see this example run. Notice how it prints out the same data structure that I used above.
If you do the same in your question, this will force you to clean up your data so that it is actually valid. Then you are giving people something they can work with.
One other note: don't be hung up on trying to do this in a "functional" manner. It's very likely that you will get more understandable code by creating an empty array with let output = [];, then using .forEach() on each of your nested arrays (or for...of loops if you are targeting the latest browsers), and using output.push() on each matching element.
To illustrate, assuming I understand your data structure correctly (and assuming you wrap it inside an input variable as in my simplified example) it might look something like this:
let output = [];
input.data.forEach( function( dataItem ) {
dataItem.services.forEach( function( service ) {
service.history.forEach( function( historyItem ) {
if( ! historyItem.completed && historyItem.status == "stage2" ) {
output.push( historyItem );
}
});
});
});
Or using for...of loops:
let output = [];
for( let dataItem of input.data ) {
for( let service of dataItem.services ) {
for( let historyItem of service.history ) {
if( ! historyItem.completed && historyItem.status == "stage2" ) {
output.push( historyItem );
}
}
}
}
Both of these are untested, of course. And either way it's not fancy, but it seems pretty easy to understand.
Depending on how you want the result data, here's a start for you. You can brute-force this with a few nested filters:
result = data.filter((datum) => {
return datum.services.filter((service) => {
return service.history.filter((h) => {
return h.completed && h.status === "stage2"
}).length > 0;
}).length > 0;
});
tl;dr - Filter the main list by any datum that has services that have at least one history record that was completed in stage 2.
Working fiddle: http://jsbin.com/jozujezidu/edit?js,console,output
If you want your resultant array to only have the history records that pass the filter, you'll have to modify the code. Plus, this is an On^3, so if this data can be enormous, you should probably modify the approach. But this should get you going.
Don't worry about being militant functional. If you can come to a working solution that people can understand and maintain, then that's a good start.
A filter operation will be based on a predicate matching your values.
If you are wanting a list of the service objects try this approach:
let result = data[0].services.filter((item) => item.history.some((h) => h.status=='stage2' && h.completed==false));
I've got an aggregation that, right now, returns objects looking like:
"_id": ObjectId("58f15197315e16762fbd2f0d"),
"versionCount": 3,
"article": {
"_id": ObjectId("58f152ecd549c4783a84f844"),
"otherProps": "etc..."
}
I've gone through quite a few aggregation steps to get here. There are quite a few properties under article. Problem is, I want it to return articles with the versionCount property. I could do a $project and individually assign each property to the parent document, but that would take many lines of code and be relatively fragile. Is there a more efficient way to take all of the properties from article and assign them to the documents returned by the aggregation?
You can use $addFields to add the top level fields to the sub document and use $replaceRoot to promote sub document to top level.
db.collection.aggregate({
$addFields: {
"article.doc_id":"$_id",
"article.versionCount": "$versionCount"
}
}, {
$replaceRoot: {
newRoot: "$article"
}
})
In couchdb I need to filter by key and which is done like this.
{
"_id": "_design/test",
"_rev": "6-cef7048c4fadf0daa67005fefe",
"language": "javascript",
"views": {
"all": {
"map": "function(doc) { if (doc.blogId) {emit(doc.key, doc);} }"
}
}
}
However the results should be ordered by another key (doc.anotherkey). So using the same function how do I achieve both filtering and ordering by another key.
Thank you
If you only need to query by single key, you can use the following map:
function (doc) {
if (doc.blogId) {
emit([doc.key, doc.anotherkey], 1);
}
}
and query for "KEY" with ?startkey=["KEY"]&endkey=["KEY",{}]&include_docs=true.
Here, according to the collation specification of CouchDB:
["KEY"] is a value lesser than any ["KEY","OTHER"] value (because longer arrays sort after their prefixes), but greater than any ["KEY2","OTHER"] with "KEY2" < "KEY";
and ["KEY",{}] is a value greater than any ["KEY","OTHER"] value, if doc.otherkey is never a JSON object (because JSON objects comes after any other JSON value), but lesser than any ["KEY2","OTHER"] with "KEY2" > "KEY".
Of course this is not limited to strings. Any type of value will work, as long as the collation is right.
Remember to URL encode the values in startkey and endkey. For example, using curl and assuming your database is "DB":
curl 'http://localhost:5984/DB/_design/test/_view/all?startkey=%5B%22KEY%22%5D&endkey=%5B%22KEY%22,%7B%7D%5D&include_docs=true'
Note that I've used the include_docs query parameter, instead of emitting the entire document with emit(..., doc), to save disk space. Query parameters are documented on CouchDB documentation.
To sort results in descending order, use the descending=true query parameter and swap the values of startkey and endkey as documented in the definitive guide book.
curl 'http://localhost:5984/DB/_design/test/_view/all?endkey=%5B%22KEY%22%5D&startkey=%5B%22KEY%22,%7B%7D%5D&include_docs=true&descending=true'
I'm trying to generate a tree structure in JavaScript from a flat array. This would usually be a fairly straightforward proposition - simply retain a 'stack' array with references to ancestor objects of the current working scope ordered by nesting depth - push a new element onto the stack when entering another nested level, and pop it off when leaving one, replacing the current working element with the object referenced by the (new) last array item.
Unfortunately this requires the capability to pass-by-reference, which JavaScript doesn't have (well, doesn't have in any meaningful way that I know how I could use for this problem.)
To give a bit of background, I'm trying to turn an arbitrarily long/complicated string containing nested XML-style (but not XML, so an XML parser can't be used instead) tokens into a structure similar to the one below:
Expected Input:
[
"<token>",
"<my non compliant token>",
"some text at this level",
"<some other token>",
"some more text",
"<yet another token>",
"more text",
"</yet another token>",
"blah!",
"</some other token>",
"</token>",
"more text"
]
Expected Output
[
{
"token": "<token>",
"children": [
{
"token": "<my non compliant token>",
"children": [
"some text at this level",
{
"token": "<some other token>",
"children": [
"some more text",
{
"token": "<yet another token>",
"children": [ "more text" ]
},
"blah!"
]
}
]
}
]
},
"more text"
]
To clarify - I'm not after an entire algorithm (but I'd be interested if you want to provide your implementation) - just a good method for maintaining current position in the outputted tree (or an entirely different/better way of generating tree objects!) Don't get too caught up on how the tokens work - they're not XML and for the purpose of the exercise could be formatted entirely differently.
Any input would be greatly appreciated!
Your strings look easy to parse. I think I would do something like this:
var stack = [];
var array = [];
for (var i in strings) {
var s = strings[i];
if (s.indexOf("</") == 0) {
array = stack.pop();
} else if (s.indexOf("<") == 0) {
var obj = {token: s, children: []};
array.push(obj);
stack.push(array);
array = obj.children;
} else {
array.push(s);
}
}
Idea #1
Here's an answer you probably weren't anticipating.
Looking at your expect output, I was wondering if it's easiest to just generate JSON and then eval it when you're done. No references at all.
When going through your flat array, you basically have three operations:
You add more data to the current object
You close off the current object
You create a new child object
You can do all three of those fairly easily by just appending the appropriate text onto a JSON string you're building as you iterate through your source array to literally just generate the text you show in your expected output. When done, run that JSON string through eval. You may need a few safety checks to verify that each array and object is closed properly if there are errors in the input, but it should work fine.
Idea #2
You can still use your stack array. I'm not sure exactly why you need to pass by reference, but you can just pass an index into the array around and have everyone modify the master copy of the array that way via index. Using local functions, the master array can be a common data value that is local to your main function, but essentially global to all your sub-functions so they can all shared access to it.
This would look something like this:
function ParseRawData(rawData)
{
var parentScopeArray = []; // main parent scope of objects
function processTag(x)
{
// you can access parentScopeArray directly here and
// and be accessing it by reference
}
// other code or local functions here
}
Idea #3
If you want to pass the array into a function and have the master copy modified (perhaps the reason you're thinking of pass by reference), the javascript design pattern is to pass the array in and return a modified array, replacing the entire original array with the modified one that is returned.