I am designing a document structure and use spring-data-mongodb to access it. The document structure is to store device profile. Each device contains modules of different types. The device can contains multiple modules of the same type. Module types are dynamic as new type of modules are created sometimes.
Please note: I try not to write custom queries to avoid boilerplate code. But, some custom queries should be fine.
I come out with two designs:
the first one use dynamic field (i.e. map). Semantics is better but seems harder to query/update using spring-data-mongodb.
{
deviceId: "12345",
instanceTypeMap: {
"type1": {
moduleMap: {
"1": {field1: "value",field2: "value"},
"2": {field1: "value",field2: "value"}
}
},
"type2": {
moduleMap: {
"30": {fielda: "value",fieldb: "value"},
"45": {fielda: "value",fieldb: "value"}
}
}
}
the second one use array and query/update seems more in-line with spring-data-mongodb.
{
deviceId: "12345",
allInstances: [
{
type: 1,
modules: [
{
id: 1,
field1: "value",
field2: "value"
},
{
id: 2,
field1: "value",
field2: "value"
}
]
},
{
type: 2,
modules: [
{
id: 30,
fielda: "value",
fieldb: "value"
},
{
id: 45,
fielda: "value",
fieldb: "value"
}
]
}
]
}
I am inclined to use array. Is it better to use array instead of dynamic field with spring-data-mongodb. I did some search on-line and found people mentioned that query for key (i.e. in map) is not as easy in spring-data-mongodb. Is that a correct statement? Do I miss anything? Thank you in advance.
I ended up with the design as below. I use one device-instance-type per document. Because, in some scenario,
updates are done on many modules of the same instance type. Those updates can be aggregated as just one database update.
The redundant "moduleId" field is also added for query purpose.
{
deviceId: "12345",
instanceTypeId: "type1",
moduleMap: {
"1": {
moduleId: "1",
field1: "value",
field2: "value"
},
"2": {
moduleId: "2",
field1: "value",
field2: "value"
}
}
}
Now, I can use spring-data-mongodb's query:
findByDeviceId("12345");
findByDeviceIdAndInstanceTypeId("12345","type1");
findByDeviceIdAndInstanceTypeIdAndModuleMapModuleId("12345","type1","1");
Related
I have a collection with a layout that looks something like this:
student1 = {
"First_Name": "John",
"Last_Name": "Doe",
"Courses": [
{
"Course_Id": 123,
"Course_Name": "Computer Science",
"Has_Chosen_Modules": false
},
{
"Course_Id": 284,
"Course_Name": "Mathematics",
"Has_Chosen_Modules": false
}
]
};
I also have the following update query:
db.Collection_Student.update(
{
$and: [
{First_Name: "John"},
{Last_Name: "Doe"}
]
},
{
$set : { "Courses.0.Has_Chosen_Modules" : true }
}
);
This code will currently update the Computer Science Has_Chosen_Modules value to true since the index is hardcoded. However, what if I wanted to update the value of Has_Chosen_Modules via the Course_Id instead (as the course might not necessarily be at the same index every time)? How would I achieve this without it affecting the other courses that a given student is taking?
You can select any item in the sub array of your document by targeting any property in the sub array of your document by using dot .
You can easily achieve this by the following query.
db.Collection_Student.update(
{
First_Name: "John",
Last_Name: "Doe",
'Courses.Course_Id': 123
},
{
$set : { "Courses.$.Has_Chosen_Modules" : true }
}
);
Conditions in search filter are by default treated as $and operator, so you don't need to specifically write $and for this simple query.
I am learning MongoDB and I've encountered a thing that mildly annoys me.
Let's say I got this collection:
[
{
_id: ObjectId("XXXXXXXXXXXXXX"),
name: "Tom",
followers: 10,
active: true
},
{
_id: ObjectId("XXXXXXXXXXXXXX"),
name: "Rob",
followers: 109,
active: true
},
{
_id: ObjectId("XXXXXXXXXXXXXX"),
name: "Jacob",
followers: 2,
active: false
}
]
and I rename the name column to username with the command:
db.getCollection('users').update({}, { $rename: { "name" : "username" }}, false, true)
now the username property is at the end of the record, example:
[
// ... rest of collection has the same structure
{
_id: ObjectId("XXXXXXXXXXXXXX"),
followers: 109,
active: true,
username: "Rob"
}
// ... rest of collection has the same structure
]
How do I prevent this from happening or how do I place them in a specific order? This is infuriating to work with in Robo/Studio 3T. I've got a collection with about 15 columns which are now out of order which in the GUI because of this
The $rename operator logically performs an $unset of both the old name and the new name, and then performs a $set operation with the new name. As such, the operation may not preserve the order of the fields in the document; i.e. the renamed field may move within the document.
Documentation
It is the behaviour from version 2.6
Since it is JSON based, you can get any field easily. And you have very less columns.
Keys in JSON objects are in their very nature unordered. See RFC 4627 which defines JSON, section 1 "Introduction":
An object is an unordered collection of zero or more name/value
pairs, where a name is a string and a value is a string, number,
boolean, null, object, or array.
(Emphasis mine)
Therefore, it would even be correct, if you wrote
{
"name": "Joe",
"city": "New York"
}
and got back
{
"city": "New York",
"name": "Joe"
}
Which of these document models would be better to use in MongoDB?
Animal:
{
_id: "1",
name: "abc",
locations_spotted: [
{
locId: "1",
dates: ["1-1-2009", "12-4-2013"...]
},
{
locId: "2",
dates: ["3-1-2012", "12-3-2013"...]
}
...
]
}
Animal:
{
_id: "1",
name: "abc",
loc1spotdates: ["1-1-2009", "12-4-2013"...],
loc2spotdates: ["3-1-2012", "12-3-2013"...],
...
...
}
There are a limited number of locations and only a few might get added in the future.
First variant is better in my opinion. Because in future if you prefer to add additional information you add it right into the object inside array. You leave your options open. In future you could add time of the day also maybe.
Suppose I have several documents like so
{
title: 'blah',
value: {
"A": {property: "foo"},
"B": {property: "bar"},
"C": {property: "foo"},
"D": {property: "foo"}
}
}
{
title: 'blah2',
value: {
"A": {property: "bar"},
"B": {property: "bar"},
"C": {property: "bar"},
"D": {property: "foo"}
}
}
What mongodb query will get me all of the documents / hash keys that have {property: "foo"}
(I know this can be done using js after the query, but can it be done within the query itself?)
The trouble is that there's no wildcard for object keys (see https://jira.mongodb.org/browse/SERVER-267), so you wouldn't be able to do this without listing all of the keys in your "value". That might be an option if you know what all of the keys are, but I imagine you don't.
If you converted "value" to an array rather than an object, you could do a query easily (which would return the documents, not the hash keys).
As the first answer says, there is nothing in the mongodb query language that would allow you to do this type of query.
You might want to consider altering your schema to make value an array like this:
value: [
{ name : "A", property : "bar" },
{ name : "B", property : "bar" },
{ name : "C", property : "bar" },
{ name : "D", property : "foo" }
]
Then you could index on value.property and run a query on value.property = "foo".
How do I make this query in mongoDB?
{
_id: "*******"
content: "",
comments: [
{
key1: "1",
key2: "2"
},
{
key1: "sdfs",
key2: "sdfasdf"
}
]
}
For example, I use the data as below. I want to query the items in comments in condition {key1: 1, key2: 2}, and not return the whole record.
What should I do?
You can try to this one
{ "comments.key1" : "1", "comments.key2" : "sdfasdf" }
You only need to use this when more than one field must be matched in the array element.
You can query a subdocument on two fields using $elemMatch:
{ comments: { $elemMatch : { key1: 1, key2: 2 } } }
You cannot return just the selected subdocument. You'll get all of them. So you'll have to filter on the client side. (You can of course, exclude all other fields of the main document).