so i have the below query that does NOT return anything when it should.
db.food.find({ingredient : {name : {$ne : "Kahlua"}}}); //empty data
However, what i think is its equivalent does output the correct info:
db.food.find({"ingredient.name" : {$ne : "Kahlua"}}); //gives correct data
I tried this using the BrowserShell for the above 2 queries, and it hasn't given me much problem for simple functions and queries.
No, they are not the same.
db.food.find({"ingredient.name" : {$ne : "Kahlua"}});
is saying "find where the ingredient name is not equal to Kahlua", whereas...
db.food.find({ingredient : {name : {$ne : "Kahlua"}}});
is saying "find where the ingredient sub object consists of a name property only, where that name is not equal to Kahlua". So in this case you're actually performing a search on the whole subject.
Probably far better explained here - dot notation vs subobjects
Related
I'm getting puzzled more and more discovering how mongodb is overcomplicated and bad designed in the query writing, anyway I have this kind of document in a db with thousand of records:
db.messages.aggregate([{$limit: 1}]).pretty()
{
"_id" : ObjectId("4f16fc97d1e2d32371003f42"),
"body" : "Hey Gillette,\n\nThe heat rate is going to depend on the type of fuel and the construction \ndate of the unit. Unfortunately, most of that info is proprietary. \n\nChris Gaskill is the head of our fundamentals group and he might be able to \nsupply you with some of the guidelines.\n\n-Bass\n\n\n \n\tEnron North America Corp.\n\t\n\tFrom: Lisa Gillette 04/05/2001 02:31 PM\n\t\n\nTo: Eric Bass/HOU/ECT#ECT\ncc: \nSubject: Power Generation Question\n\nHey Bass,\n\nI have a question and I am hoping you can help me. I am wanting to compile a \nlist of all the different types of power plants and their respective heat \nrates to determine some sort of generation ratio.\n\ni.e. Coal 4 mmbtu = 1 MW\n Simple Cycle 11 mmbtu = 1 MW\n\nPlease let me know if you can help me or point me to someone who can. Just \nFYI...Bryan suggested that I call you so blame him as you curse me under your \nbreath right now.\n\nThanks,\nLisa\n\n",
"filename" : "1045.",
"headers" : {
"Content-Transfer-Encoding" : "7bit",
"Content-Type" : "text/plain; charset=us-ascii",
"Date" : ISODate("2001-04-05T14:45:00Z"),
"From" : "eric.bass#enron.com",
"Message-ID" : "<2106897.1075854772243.JavaMail.evans#thyme>",
"Mime-Version" : "1.0",
"Subject" : "Re: Power Generation Question",
"To" : [
"lisa.gillette#enron.com"
],
"X-FileName" : "ebass.nsf",
"X-Folder" : "\\Eric_Bass_Jun2001\\Notes Folders\\Sent",
"X-From" : "Eric Bass",
"X-Origin" : "Bass-E",
"X-To" : "Lisa Gillette",
"X-bcc" : "",
"X-cc" : ""
},
"mailbox" : "bass-e",
"subFolder" : "sent"
}
And I need to find records from address X to address Y.
I managed to catch the "From" records with
db.messages.find({"headers.From": "eric.bass#enron.com"}).pretty().count()
But I can't get the To records (and I Need to get both togheter).
To query the "To" field I've tried:
db.messages.find({headers: {$elemMatch :{ "To": "lisa.gillette#enron.com"}}})
But it returns nothing
What am I missing?
Thanks
$elemMatch - To use this operator we need to give the array element and the matching operator, here in your case it should be like
db.messages.find({"headers.To": {$elemMatch :{$eq:"lisa.gillette#enron.com"}}})
$elemMatch is optimal to use when we have multiple queries to given for the array elements. If we are specifying only a single condition in the $elemMatch expression, we don't need to use $elemMatch, instead we can use find
db.messages.find({"headers.To": "lisa.gillette#enron.com"});
My question was, how to find all title of the releases contains the artist name
Here is the 2 Documents for just an example:
`{"release" : {"title" : "DEF day",
"artists" : {"artist" : {"role" : "1","name" : "DEF"}}}
}
{ "release" : {"title" : "XYZ day",
"artists" : {"artist" : {"role" : "1","name" : "KYC"}}}
}`
when i run this following query:
`db.test.find({$where:
"this.release.title.indexOf(this.release.artists.artist.name) > -1"
})`
I get the result "DEF day", so it works excellent!!
BUT, once i run this query to my original data(same format like above) i get this:
`error: {
"$err" : "TypeError: Object 30 has no method 'indexOf'\n at _funcs1 (_funcs1:1:49) near 'his.release.artists.a' ",
"code" : 16722
}`
My collection is big (8GB+).
Just looking at the above error, can anyone tell what may be the problem with the above query? your answer is appreciated. please.
The problem is in the data itself. Somewhere you have a document, where the title field is not String, thus invoking indexOf on the whole data, on that particular document you get the error.
One thing you can do to solve this problem is first of all find that erroneous document. To do that you will need to run a simple query.
MongoDB has the $type operator, which matches fields by their type. And here is the list of all available BSON types a MongoDB document field can have.
The id of String BSON type is 2, thus you need all the documents that have type of title field not equal to 2.
find({field: {$not: {$type: <BSON type>}}}))
After finding the document(s), you may fix or remove them.
I have contact documents which contain an embedded document "lead". So the data would look like this:
{
"_id" : ObjectId("54f8fa496d6163ad64010000"),
"name" : "teretyrrtuyytiuyi",
"email" : "rertytruyy#fdgjioj.com",
"fax" : "",
"birth_date" : null,
"phone" : "dfgdfhfgjg",
"phone_2" :
"hgjhkhjkljlj",
"lead" : { "_id" : ObjectId("54f8fa496d6163ad64020000"), "appointment status" : "dfhgfgjghjk" }
}
When there are many contacts, there will be many leads. I want to retrieve all the leads in the collection, without retrieving the owning contact. I tried the following but none seem to work:
db.lead.find()
db.contacts.find({ 'lead.$' : 1})
Any way to do this?
If that query makes sense for you, you should have probably used a different data structure. If your embedded document has an id, it is almost certainly supposed to be a first-level citizen instead.
You can work around this using the aggregation framework, but I'd consider that a hack that probably works around some more profound problem with your data model.
It's also not very elegant:
>
> db.contacts.aggregate({ $project : {
"appointment_status" : "$lead."appointment_status",
"lead_id" : "$lead.id", ... } });
>
That way, it'll look as if leads was a collection of its own, but it's not and this is just a bad hack around it.
Note that there's no wildcard operator, so if you want to have all fields projected to the root level, you'll have to do it manually. It'd be much easier to simply read the regular documents - if that's not what you need, correct your schema design.
I have a collection with following document:
{
"_id" : ObjectId("51f1fd2b8188d3117c6da352"),
"cust_id" : "abc1234",
"ord_date" : ISODate("2012-10-03T18:30:00Z"),
"status" : "A",
"price" : 27,
"items" : [{
"sku" : "mmm",
"qty" : 5,
"price" : 2.5
}, {
"sku" : "nnn",
"qty" : 5,
"price" : 2.5
}]
}
I want to use "$where" in the fields of "items", so something like this:
{$where:"this.items.sku==mmm"}
How can I do it? It works when the field is not of array type.
You don't need a $where operator to do this; just use a query object of:
{ "items.sku": mmm }
As for why your $where isn't working, the value of that operator is executed as JavaScript, so that's not going to check each element of the items array, it's just going to treat items as a normal object and compare its sku property (which is undefined) to mmm.
You are comparing this.items.sku to a variable mmm, which isn't initialized and thus has the value unefined. What you want to do, is iterate the array and compare each entry to the string 'mmm'. This example does this by using the array method some which returns true, when the passed function returns true for at least one of the entries:
{$where:"return this.items.some(function(entry){return entry.sku =='mmm'})"}
But really, don't do this. In a comment to the answer by JohnnyHK you said "my service is just a interface between user and mongodb, totally unaware what the field client want's to store". You aren't really explaining your use-case, but I am sure you can solve this better.
The $where operator invokes the Javascript engine even though this
trivial expression could be done with a normal query. This means unnecessary performance overhead.
Every single document in the collection is passed to the function, so when you have an index, it can not be used.
When the javascript function is generated from something provided by the client, you must be careful to sanetize and escape it properly, or your application gets vulnerable to code injection.
I've been reading through your comments in addition to the question. It sounds like your users can generically add some attributes, which you are storing in an array within a document. Your client needs to be able to query an arbitrary pair from the document in a generic manner. The pattern to achieve this is typically as follows:
{
.
.
attributes:[
{k:"some user defined key",
v:"the value"},
{k: ,v:}
.
.
]
}
Note that in your case, items is attributes. Now to get the document, your query will be something like:
eg)
db.collection.find({attributes:{$elemMatch:{k:"sku",v:"mmm"}}});
(index attributes.k, attributes.v)
This allows your service to provide a way to query the data, and letting the client specify what the k,v pairs are. The one caveat with this design is always be aware that documents have a 16MB limit (unless you have a use case that makes GridFS appropriate). There are functions like $slice which may help with controlling this.
Gurus - I'm stuck in a situation that I can't figure out how I can query from the following collection "spouse", which has embedded document "surname" and check for equality with "surname" of this document:
{
"_id" : ObjectId("50bd2bb4fcfc6066b7ef090d"),
"name" : "Gwendolyn",
"surname" : "Davis",
"birthyear" : 1978,
"spouse" : {
"name" : "Dennis",
"surname" : "Evans",
"birthyear" : 1969
},
I need to query:
Output data for all spouses with the same surnames (if the surname of
one of the spouses is not specified, assume that it coincides with the
name of another)
I tried something like this:
db.task.find( {"surname" : { "spouse.surname" : 1 }} )
but it failed)
PLEASE PLEASE Guide me how I can achieve this any example/sample? based on this will be really helpful :-)
Thanks a lot!
You have three options.
Use $where modifier:
db.task.find({$where: 'this.spouse.surname === this.surname'})
Update all your documents and add special flag. After that you will be able to query documents by this flag. It's faster then $where, but requires altering your data.
Use MapReduce. It's quite complicated, but it allows you to do nearly anything.