For the following JSON how do I remove the dog whose height is the least
{
_id:0
"name":"Andy",
"pets":[
{
"type":"dog","name":"max","height":120
},
{
"type":"dog","name":"rover","height":44
},
{
"type":"dog","name":"katie","height":100
},
{
"type":"cat","name":"minni"
}
]
}
The problem is the array of subdocuments is not a collection, you can't sort or do something else on it. But if you have an access to any language interface like JavaScript or else it's possible. You just need to extract list of subdocuments, sort them by height, remember the first one and then run the command to pull it from the array based on its name and height.
It can be done for example using this JavaScript code right in the MongoDB shell:
var min = 0; var name = "";
db.animals.find({ query:{"_id" : 0} }).forEach(
function(record){
var sets = record.pets;
min = sets[0].height;
sets.forEach(function(set){
if(set.height <= min)
{min=set.height;
name=set.name;}
});
print(min);
print(name);
query = {"_id": 0}
update = { "$pull" : { "pets" : { "name" : name } } };
db.animals.update(query, update);
})
I suspect the solution is not the most elegant but anyway it works.
Related
I have a database like this:
[
{
"universe":"comics",
"saga":[
{
"name":"x-men",
"characters":[
{
"character":"wolverine",
"picture":"618035022351.png"
},
{
"character":"cyclops",
"picture":"618035022352.png"
}
]
}
]
},
{
"universe":"dc",
"saga":[
{
"name":"spiderman",
"characters":[
{
"character":"venom",
"picture":"618035022353.png"
}
]
}
]
}
]
and with this code I manage to update one of the objects in my array. specifically the object where character: wolverine
db.mydb.findOneAndUpdate({
"universe": "comics",
"saga.name": "x-men",
"saga.characters.character": "wolverine"
}, {
$set: {
"saga.$[].characters.$[].character": "lobezno",
"saga.$[].characters.$[].picture": "618035022354.png",
}
}, {
new: false
}
)
it returns all my document, I need ONLY the document matched
I would like to return the object that I have updated without having to make more queries to the database.
Note
I have been told that my code does not work well as it should, apparently my query to update this bad, I would like to know how to fix it and get the object that matches these search criteria.
In other words how can I get this output:
{
"character":"wolverine",
"picture":"618035022351.png"
}
in a single query using filters
{
"universe": "comics",
"saga.name": "x-men",
"saga.characters.character": "wolverine"
}
My MongoDB knowledge prevents me from correcting this.
Use the shell method findAndModify to suit your needs.
But you cannot use the positional character $ more than once while projecting in MongoDb, so you may have to keep track of it yourself at client-side.
Use arrayFilters to update deeply nested sub-document, instead of positional all operator $[].
Below is a working query -
var query = {
universe: 'comics'
};
var update = {
$set: {
'saga.$[outer].characters.$[inner].character': 'lobezno',
'saga.$[outer].characters.$[inner].picture': '618035022354.png',
}
};
var fields = {
'saga.characters': 1
};
var updateFilter = {
arrayFilters: [
{
'outer.name': 'x-men'
},
{
'inner.character': 'wolverine'
}
]
};
db.collection.findAndModify({
query,
update,
fields,
arrayFilters: updateFilter.arrayFilters
new: true
});
If I understand your question correctly, your updating is working as expected and your issue is that it returns the whole document and you don't want to query the database to just to return these two fields.
Why don't you just extract the fields from the document returned from your update? You are not going to the database when doing that.
var extractElementFromResult = null;
if(result != null) {
extractElementFromResult = result.saga
.filter(item => item.name == "x-men")[0]
.characters
.filter(item => item.character == "wolverine")[0];
}
I'm dont think that this is a Meteor specific question, but rather around mongo and building mongo queries.
If I have the following structure,
{
username : someName,
contacts : [
{
userid : asdfae33rtqqxxx,
name : contactName,
status : friend
}
{
userid : asdfae33rtqqxxx,
name : anotherName,
status : pending
}
{
userid : asdfae33rtqqxxx,
name : contactName,
status : blocked
}
]
}
How could I pass in values from this array into a query against the users collection, to a) get the users in this array, or b) get all users in this array from the users collection with a particular status.
If this is not possible, how should I adjust my schema in order to make these sorts of queries possible?
This function will return a Meteor.users cursor based on an array of contacts and an optionally required status:
var usersByContacts = function(contacts, requiredStatus) {
var userIds = _.chain(contacts)
.map(function(c) {
if (requiredStatus) {
if (c.status === requiredStatus)
return c.userid;
} else {
return c.userid;
}
})
.compact()
.value();
return Meteor.users.find({_id: {$in: userIds}});
};
You can use it like this:
var users1 = usersByContacts(thing.contacts);
var users2 = usersByContacts(thing.contacts, 'pending');
This assumes thing has the schema referenced in your question. Also note that if you find this is a common pattern in your code, you should consider turning usersByContacts into a transform.
In Mongo how can I find all documents that have a given key and value, regardless of where that key appears in the document's key/value hierarchy?
For example the input key roID and value 5 would match both:
{
roID: '5'
}
and
{
other: {
roID: '5'
}
}
There is no built in way to do this. You might have to scan each matched document recursively to try and locate that attribute. Not recommended. You might want to think about restructuring your data or perhaps manipulating it into a more unified format so that it will be easier (and faster) to query.
If your desired key appears in a fixed number of different locations, you could use the $or operator to scan all the possibilities.
Taking your sample documents as an example, your query would look something like this:
db.data.find( { "$or": [
{ "roID": 5 },
{ "other.roID": 5 },
{ "foo.bar.roID": 5 },
{ any other possbile locations of roID },
...
] } )
If the number of documents in collection is not so large, then it can be done by this:
db.system.js.save({_id:"keyValueExisted", value: function (key, value) {
function findme(obj) {
for (var x in obj) {
var v = obj[x];
if (x == key && v == value) {
return true;
} else if (v instanceof Object) {
if (findme(v)) return true;
}
}
return false;
}
return findme(this);
}});
var param = ['roID', '5'];
db.c.find({$where: "keyValueExisted.apply(this, " + tojsononeline(param) + ");"});
Here's the structure part of my collection :
{
_id: {
id:"6a6ca923517f304900badd98",
target:"00badd6a6ca923517f304998e4df"
},
...
}
The use of :
if(bson_find(iterator, mongo_cursor_bson(cursor), "_id")){
bson_iterator_subiterator(iterator, sub);
id = (char*)bson_iterator_string(sub);
}
is "working" but in reality simply returns me the result of the first field of the array found...
How to recover precisely the value of the "id" or "target" field please ?
You can also use bson_iterator_more and bson_iterator_next upon the sub-iterator(It was still an iterator).
try this:
if(bson_find(iterator, mongo_cursor_bson(cursor), "_id"))
{
bson_iterator_subiterator(iterator, sub);
while(bson_iterator_more(sub))
{
if (bson_iterator_next(sub) != BSON_EOO)
{
printf("%s: %s\n", bson_iterator_key(sub), bson_iterator_string(sub));
}
}
}
I have a MongoDB collection containing history data with id and timestamp.
I want to delete data from the collection older than a specific
timestamp. But for every id at least one
document (the newest) must stay in the collection.
Suppose I have the following documents in my collection ...
{"id" : "11", "timestamp" : ISODate("2011-09-09T10:27:34.785Z")} //1
{"id" : "11", "timestamp" : ISODate("2011-09-08T10:27:34.785Z")} //2
{"id" : "22", "timestamp" : ISODate("2011-09-05T10:27:34.785Z")} //3
{"id" : "22", "timestamp" : ISODate("2011-09-01T10:27:34.785Z")} //4
... and I want to delete documents having a timestamp older than
2011-09-07 then
1 and 2 should not be deleted because they are newer.
4 should be deleted because it is older, but 3 should not be deleted
(although it is older) because
at least one document per id should stay in the collection.
Does anyone know how I can do this with casbah and/or on the mongo
console?
Regards,
Christian
I can think of a couple of ways. First, try this:
var cutoff = new ISODate("2011-09-07T00:00:00.000Z");
db.testdata.find().forEach(function(data) {
if (data.timestamp.valueOf() < cutoff.valueOf()) {
// A candidate for deletion
if (db.testdata.find({"id": data.id, "timestamp": { $gt: data.timestamp }}).count() > 0) {
db.testdata.remove({"_id" : data._id});
}
}
});
This does the job you want. Or you can use a MapReduce job to do it as well. Load this into a text file:
var map = function() {
emit(this.id, {
ref: this._id,
timestamp: this.timestamp
});
};
var reduce = function(key, values) {
var cutoff = new ISODate("2011-09-07T00:00:00.000Z");
var newest = null;
var ref = null;
var i;
for (i = 0; i < values.length; ++i) {
if (values[i].timestamp.valueOf() < cutoff.valueOf()) {
// falls into the delete range
if (ref == null) {
ref = values[i].ref;
newest = values[i].timestamp;
} else if (values[i].timestamp.valueOf() > newest.valueOf()) {
// This one is newer than the one we are currently saving.
// delete ref
db.testdata.remove({_id : ref});
ref = values[i].ref;
newest = values[i].timestamp;
} else {
// This one is older
// delete values[i].ref
db.testdata.remove({_id : values[i].ref});
}
} else if (ref == null) {
ref = values[i].ref;
newest = values[i].timestamp;
}
}
return { ref: ref, timestamp: newest };
};
Load the above file into the shell: load("file.js");
Then run it: db.testdata.mapReduce(map, reduce, {out: "results"});
Then remove the mapReduce output: db.results.drop();