I have the following documents inside a folders collection:
folders: [
{ _id : 1,
docs : [
{ foo : 1,
bar : undefined},
{ foo : 3,
bar : 3}
]
},
{ _id : 2,
docs : [
{ foo : 2,
bar : 2},
{ foo : 3,
bar : 3}
]
},
{ _id : 3,
docs : [
{ foo : 2},
{ foo : 3,
bar : 3}
]
},
{ _id : 4,
docs : [
{ foo : 1 }
]
},
{ _id : 5,
docs : [
{ foo : 1,
bar : null }
]
}
]
I need to be able to query the documents that do not have an undefined value, null value, or non-existent value for docs.bar. In the case above, the query should only return the document with _id: 2. I currently have a solution but I was wondering if there is a better way to query the documents.
My current solution:
db.folders.find({$nor: [{"docs.bar": { $exists: false }}]})
This ...
db.folder.find({"docs.bar": {$exists: true}, "docs.bar": {$ne: null}})
... will return only those entries for which at least one of the sub documents in the docs array has a populated bar attribute. Note: in this query the two predicates are ANDed, I think that matches your requirements, it certainly returns the document with _id: 2 from the set you supplied.
Related
I'm trying to select any documents where privacy settings match the provided ones and any documents which do not have any privacy settings (i.e. public).
Current behavior is that if I have a schema with an array of object ids referenced to another collection:
privacy: [{
type: mongoose.Schema.Types.ObjectId,
ref: 'Category',
index: true,
required: true,
default: []
}],
And I want to filter all content for my categories and the public ones, in our case content that does not have a privacy settings. i.e. an empty array []
We currently query that with an or query
{"$or":[
{"privacy": {"$size": 0}},
{"privacy": {"$in":
["5745bdd4b896d4f4367558b4","5745bd9bb896d4f4367558b2"]}
}
]}
I would love to query it by only providing an empty array [] as one the comparison options in the $in statement. Which is possible in mongodb:
db.emptyarray.insert({a:1})
db.emptyarray.insert({a:2, b:null})
db.emptyarray.insert({a:2, b:[]})
db.emptyarray.insert({a:3, b:["perm1"]})
db.emptyarray.insert({a:3, b:["perm1", "perm2"]})
db.emptyarray.insert({a:3, b:["perm1", "perm2", []]})
> db.emptyarray.find({b:[]})
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce0"), "a" : 2, "b" : [ ] }
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce3"), "a" : 3, "b" : [ "perm1", "perm2", [ ] ] }
> db.emptyarray.find({b:{$in:[]}})
> db.emptyarray.find({b:{$in:[[], "perm1"]}})
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce0"), "a" : 2, "b" : [ ] }
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce1"), "a" : 3, "b" : [ "perm1" ] }
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce2"), "a" : 3, "b" : [ "perm1", "perm2" ] }
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce3"), "a" : 3, "b" : [ "perm1", "perm2", [ ] ] }
> db.emptyarray.find({b:{$in:[[], "perm1", null]}})
{ "_id" : ObjectId("5a305f3dd89e8a887e629cde"), "a" : 1 }
{ "_id" : ObjectId("5a305f3dd89e8a887e629cdf"), "a" : 2, "b" : null }
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce0"), "a" : 2, "b" : [ ] }
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce1"), "a" : 3, "b" : [ "perm1" ] }
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce2"), "a" : 3, "b" : [ "perm1", "perm2" ] }
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce3"), "a" : 3, "b" : [ "perm1", "perm2", [ ] ] }
> db.emptyarray.find({b:{$in:[[]]}})
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce0"), "a" : 2, "b" : [ ] }
{ "_id" : ObjectId("5a305f3dd89e8a887e629ce3"), "a" : 3, "b" : [ "perm1", "perm2", [ ] ] }
Maybe like this:
"privacy_locations":{
"$in": ["5745bdd4b896d4f4367558b4","5745bd9bb896d4f4367558b2",[]]
}
But this query, works from the console (CLI), but not in the code where it throws a cast error:
{
"message":"Error in retrieving records from db.",
"error":
{
"message":"Cast to ObjectId failed for value \"[]\" at ...
}
}
Now I perfectly understand the cast is happening because the Schema is defined as an ObjectId.
But I still find that this approach is missing two possible scenarios.
I believe it is possible to query (in MongoDB) null options or empty array within an $in statement.
array: {$in:[null, [], [option-1, option-2]}
Is this correct?
I've been thinking that the best solution to my problem (Cannot select in options or empty) could be to have empty arrays be an array with a fix option of ALL for example. A setting for privacy that means ALL instead of how it is now which is that if not set, that is considered all.
But I don't want a major refactor of the existing code, I just need to see if I can make a better query or more performant query.
Today we have the query working with an $OR statement that has issues with indexes. And even if it is fast, I wanted to bring attention to this issue even if is not considered a bug.
I will appreciate any comments or guidance.
The semi-short answer is that the schema is mixing types for the privacy property (ObjectId and Array) while declaring that it is strictly of type ObjectId in the schema.
Since MongoDB is schema-less it will allow any document shape per document and doesn't need to verify the query document to match a schema. Mongoose on the other hand is meant to apply a schema enforcement and so it will verify a query document against the schema before it attempts to query the DB. The query document for { privacy: { $in: [[]] } } will fail validation since an empty array is not a valid ObjectId as indicated by the error.
The schema would need to declare the type as Mixed (which doesn't support ref) to continue using an empty array as an acceptable type as well as ObjectId.
// Current
const FooSchema = new mongoose.Schema({
privacy: [{
type: mongoose.Schema.Types.ObjectId,
ref: 'Category',
index: true,
required: true,
default: []
}]
});
const Foo = connection.model('Foo', FooSchema);
const foo1 = new Foo();
const foo2 = new Foo({privacy: [mongoose.Types.ObjectId()]});
Promise.all([
foo1.save(),
foo2.save()
]).then((results) => {
console.log('Saved', results);
/*
[
{ __v: 0, _id: 5a36e36a01e1b77cba8bd12f, privacy: [] },
{ __v: 0, _id: 5a36e36a01e1b77cba8bd131, privacy: [ 5a36e36a01e1b77cba8bd130 ] }
]
*/
return Foo.find({privacy: { $in: [[]] }}).exec();
}).then((results) => {
// Never gets here
console.log('Found', results);
}).catch((err) => {
console.log(err);
// { [CastError: Cast to ObjectId failed for value "[]" at path "privacy" for model "Foo"] }
});
And the working version. Also note the adjustment to properly apply the required flag, index flag and default value.
// Updated
const FooSchema = new mongoose.Schema({
privacy: {
type: [{
type: mongoose.Schema.Types.Mixed
}],
index: true,
required: true,
default: [[]]
}
});
const Foo = connection.model('Foo', FooSchema);
const foo1 = new Foo();
const foo2 = new Foo({
privacy: [mongoose.Types.ObjectId()]
});
Promise.all([
foo1.save(),
foo2.save()
]).then((results) => {
console.log(results);
/*
[
{ __v: 0, _id: 5a36f01733704f7e58c0bf9a, privacy: [ [] ] },
{ __v: 0, _id: 5a36f01733704f7e58c0bf9c, privacy: [ 5a36f01733704f7e58c0bf9b ] }
]
*/
return Foo.find().where({
privacy: { $in: [[]] }
}).exec();
}).then((results) => {
console.log(results);
// [ { _id: 5a36f01733704f7e58c0bf9a, __v: 0, privacy: [ [] ] } ]
});
Unlike the other question someone asked where they wanted only one item returned. I HAVE one item returned and I need ALL of the matching objects in the array return. However the second object that matches my query is being completely ignored.
This is what one of the items in the item collection looks like:
{
name: "soda",
cost: .50,
inventory: [
{ flavor: "Grape",
amount: 8 },
{ flavor: "Orange",
amount: 4 },
{ flavor: "Root Beer",
amount: 15 }
]
}
Here is the query I typed in to mongo shell:
Items.find({"inventory.amount" : { $lte : 10} } , { name : 1, "inventory.$.flavor" : 1})
And here is the result:
"_id" : ObjectId("59dbe33094b70e0b5851724c"),
"name": "soda"
"inventory" : [
{ "flavor" : "Grape",
"amount" : 8,
}
]
And here is what I want it to return to me:
"_id" : ObjectId("59dbe33094b70e0b5851724c"),
"name": "soda"
"inventory" : [
{ "flavor" : "Grape",
"amount" : 8
},
{ "flavor" : "Orange",
"amount" : 4
}
]
I'm new to mongo and am dabbling to get familiar with it. I've read through the docs but couldn't find a solution to this though it's quite possible I overlooked it. I'd really love some help. Thanks in advance.
first u can get your result by this query
db.Items.find({"inventory.amount" : { $lte : 10} } , { name : 1, "inventory.flavor" : 1 , "inventory.amount" : 1})
Sorry for the title, but I really do not know how to make it clear. But I can show you.
Here I have insert two document
> db.test.find().pretty()
{
"_id" : ObjectId("557faa461ec825d473b21422"),
"c" : [
{
"a" : 3,
"b" : 7
}
]
}
{
"_id" : ObjectId("557faa4c1ec825d473b21423"),
"c" : [
{
"a" : 1,
"b" : 3
},
{
"a" : 5,
"b" : 9
}
]
}
>
I only want to select the first document with a value which is greater than 'a' and smaller than 'b', like '4'.
But when i search, i cannot get the result i want
> db.test.find({'c.a': {$lte: 4}, 'c.b': {$gte: 4}})
{ "_id" : ObjectId("557faa461ec825d473b21422"), "c" : [ { "a" : 3, "b" : 7 } ] }
{ "_id" : ObjectId("557faa4c1ec825d473b21423"), "c" : [ { "a" : 1, "b" : 3 }, { "a" : 5, "b" : 9 } ] }
>
Because '4' is greater than the '"a" : 1' and smaller than '"b" : 9' in the second document even it is not in the same document in the array, so the second one selected.
But I only want the first one selected.
I found this http://docs.mongodb.org/manual/reference/operator/query/elemMatch/#op._S_elemMatch, but it seems the example is not suitable for my situation.
You would want to
db.test.findOne({ c: {$elemMatch: {a: {$lte: 4}, b: {$gte: 4} } } })
With your query, you are searching for documents that have an object in the 'c' array that has a key 'a' with a value <= 4, and a key 'b' with a value >= 4.
The second record is return because c[0].a is <= 4, and c[1].b is >= 4.
Since you specified you wanted to select only the first document, you would want to do a findOne() instead of a find().
Use $elemMatch as below :
db.test.find({"c":{"$elemMatch":{"a":{"$lte":4},"b":{"$gte":4}}}})
Or
db.test.find({"c":{"$elemMatch":{"a":{"$lte":4},"b":{"$gte":4}}}},{"c.$":1})
I create players the following way.
Players.insert({
name: name,
score: 0,
items: [{'name': 0}, {'name2': 0}...]
});
How do I increment the score in a specific player and specific item name (upserting if necessary)?
Sorry for the terrible wording :p
Well, the answer is - as in life - to simplify the problem by breaking it up.
And to avoid arrays in mongoDB - after all, objects can have as many keys as you like. So, my structure became:
{
"_id": <id>,
"name": <name>,
"score": <score>,
"items": {}
}
And to increment the a dynamic key in items:
// create your update skeleton first
var ud = { $inc: {} };
// fill it in
ud.$inc['item.' + key] = value;
// call it
db.Players.update(player, ud, true);
Works a charm :)
Lets say you have:
{
"_id" : ObjectId("5465332e6c3e2eeb66ef3683"),
"name" : "Alex",
"score" : 0,
"items" : [
{
"food" : 0
}
]
}
To update you can do:
db.Players.update({name: "Alex", "items.food": {$exists : true}},
{$inc: {score: 1, "items.$.food": 5}})
Result:
{
"_id" : ObjectId("5465332e6c3e2eeb66ef3683"),
"name" : "Alex",
"score" : 1,
"items" : [
{
"food" : 5
}
]
}
I am not sure you can upsert if the document doesn't exist because of the positional operator needed to update the array.
I have a document with an embedded collection, but few elements are missing a key and I have to find all those elements. Here is an example:
var foo = {name: 'foo', embedded: [{myKey: "1", value: 3}, {myKey: "2", value: 3}]}
db.example.insert(foo)
var bar = {name: 'bar', embedded: [{value: 4}, {myKey: "3", value: 1}]}
db.example.insert(bar)
I need a query that returns the 'bar' object because one of its embedded doesn't have the key 'myKey'.
I try to use the $exists, but it returns only if ALL embedded elements are missing the key
db.example.find({'embedded.myKey': {$exists: true}}).size()
// -> 2
db.example.find({'embedded.myKey': {$exists: false}}).size()
// -> 0
How can I find the documents that at least one embedded element is missing the key 'myKey'?
If 'value' is always present, then you can try this command
db.example.find({ embedded : { $elemMatch : { value : {$exists : true}, myKey : {$exists : false}} }})
{ "_id" : ObjectId("518bbccbc9e49428608691b0"), "name" : "bar", "embedded" : [ { "value" : 4 }, { "myKey" : "3", "value" : 1 } ] }