I have a single collection into which I am inserting documents of different types. I use the type parameter to distinguish between different datatypes in the collection. When I am inserting a document, I have created an Id field for every document, but Cosmosdb has a built-in id field.
How can I insert a new document and retrieve the id of the created Document all in one query?
The CreateDocumentAsync method returns the created document so you should be able to get the document id.
Document created = await client.CreateDocumentAsync(collectionLink, order);
I think you just need to .getResource() method to get the create document obj.
Please refer to the java code:
DocumentClient documentClient = new DocumentClient(END_POINT,
MASTER_KEY, ConnectionPolicy.GetDefault(),
ConsistencyLevel.Session);
Document document = new Document();
document.set("name","aaa");
document = documentClient.createDocument("dbs/db/colls/coll",document,null,false).getResource();
System.out.println(document.toString());
//then do your business logic with the document.....
C# code:
Parent p = new Parent
{
FamilyName = "Andersen.1",
FirstName = "Andersen",
};
Document doc = client.CreateDocumentAsync("dbs/db/colls/coll",p,null).Result.Resource;
Console.WriteLine(doc);
Hope it helps you.
Sure, you could always fetch the id from creation method response in your favorite API as already shown in other answers. You may have reasons why you want to delegate key-assigning to DocumentDB, but to be frank, I don't see any good ones.
If inserted document would have no id set DocumentDB would generate a GUID for you. There wouldn't be any notable difference compared to simply generating a new GUID yourself and assign it into id-field before save. Self-assigning the identity would let you simplify your code a bit and also let you use the identity not only after persisting but also BEFORE. Which could simplify a lot of scenarios you may have or run into in future.
Also, note that you don't have to use GUIDs as as id and could use any unique value you already have. Since you mentioned you have and Id field (which by name, I assume to be a primary key) then you should consider reusing this instead introducing another set of keys.
Self-assigned non-Guid key is usually a better choice since it can be designed to match your data and application needs better than a GUID. For example, in addition to being just unique, it may also be a natural key, narrower, human-readable, ordered, etc.
Related
I would like to see if a document exists in the database that has the name field "name" set to "a name" before allowing a new document to be added to the database.
I this possible in CouchDB using update handlers (inside design documents)?
Seems you are looking for a unique constraint in CouchDB. The only unique constraint supported by CouchDB is based on the document ID.
You should include your "name" attribute value into the document ID if you would like to have the document unicity based on it.
Validate document update functions defined in desing documents can only use the data of the document being created/updated/deleted, it can no use data from other documents in the database.
Yo can find a similar question here.
This is not widely known, but _update endpoint allowed to return a doc with _id prop different from requested. It means, in your case, you need to have an unique document say _id:"doc-name", which will serve as a constraint.
Then you call smth like POST _design/whatever/_update/saveDependentDoc/doc-name, providing new doc with different _id as a request body.
Your _update function will effectively receive two docs as an input (or null and newDoc if constraint doc is missing). The function then decides what should it do: return received doc to persist it, or return nothing.
The solution isn’t a full answer to your question, however it might be helpful in some cases.
This trick only works for updating existing docs if you know revision, for sure.
We want to check if a document already exists in the database with the same fields and values of a new object we are trying to save to prevent duplicated item.
Note: This question is not about updating documents or about duplicated document IDs, we only check the data to prevent saving a new document with the same data of an existing one.
Preferably we'd like to accomplish this with Mango/Cloudant queries and not rely on views.
The idea so far is:
1) Scan the the data that we are trying to save and dynamically create a selector that matches that document's structure. (We can't have the selectors hardcoded because we have types of many documents)
2) Query de DB with for any documents matching that selector to if any document already exists that matches those criteria.
However I wonder about the performance of this approach since many of the selector fields will not be indexed.
I also much rather follow best practices than create something out of the blue, but haven't been able to find any known solutions for this specific scenario.
If you happen to know of any, please share.
Option 1 - Define a meaningful ID for your documents
The ID could be a logical coposition or a computed hash from the values that should be unique
If you want to check if a document ID already exists you can use the HEAD method
HEAD /db/docId
which returns 200-OK if the docId exits on the database.
If you would like to check if you have the same content in the new document and in the previous one, you may use the Validate Document Update Function which allows to compare both documents.
function(newDoc, oldDoc, userCtx, secObj) {
...
}
Option 2 - Use content hash computed outside CouchDB
Before create or update a document a hash should be computed using the values of the attributes that should be unique.
The hash is included in the document in a new attribute i.e. "key_hash"
Create a mango index using the "key_hash" attribute
When a new doc should be inserted, the hash should be computed and find for documents with the same hash value using a mango expression before the doc is inserted.
Option 3 - Compute hash in a View
Define a view which emit the computed hash for each document as key
Couchdb Javascript support does not include hashing functions, this could be difficult to include in a design document.
Use erlang to define the map function, where you can access to the erlang support for hashing.
Before creating a new document you should query the view using a the hash that you need to compute previously.
One solution would be to take Juanjo's and Alexis's comment one step further.
Select the keys you wish to keep unique
Put the values in a string and generate a hash
Set the document's _id to that hash
PUT the document on the database.
check return for failure
If another document already exists on the database with the same _id value, the PUT request will fail.
I would like to generate a unique ObjectId for a resource to give back clients with the nodejs mongodb driver.
IE:
var ObjectID = require('mongodb').ObjectID;
var objectId = new ObjectID();
Reading about an ObjectId it seems that there are some cases in which this id may not be unique. Even though this is extremely rare I still cannot take a chance on having a duplicate id.
Question #1, Using this driver is it possible (even though unlikely) to get a duplicate id doing this:
var objectId = new ObjectID();
Question #2 (if above is not 100% guarantee to give a unique id):
Does this driver guarantee that for a certain collection the ObjectId that is automatically created when a new document is inserted is unique? If yes, how? If yes, can I somehow duplicate that behavior when calling new ObjectID() myself without a collection?
If the driver or the mongo server ensures (100% of the time) that for a collection every new doc gets a unique id, I could always have a collection of just ids, then when generating a new, empty doc for that collection I would ensure I get a unique ObjectId. However seems like overkill to have another collection just to store ids.
That being said some might ask why not just generate the ObjectId in a collection and update that doc later with data. The answer is that in my case data may not ever come later and I don't want to implement logic to check for empty docs that only contain an id.
It's very unlikely that the same ObjectID will generate as mongo guarantees unique ID. objectID is created with a combination of two same values and two different values (unix epoch time, and a random value). However, in any case of a duplicate, you won't be allowed to insert a document as objectID acts as a primary key and insert function will return duplicate key error to your callback. Read more here. The same error is returned if mongo node native library creates a duplicate ObjectID.
UPDATE: again after reading the code base, if "hypothetically" the objectID that was generated by the library isn't unique, the answer is no. We are not ensured by the library that the id is unique, but we are ensured of a duplicate error doesn't matter who or what sent the id.
Here's the process:
1. generates ID
2. Sends straight to server.
3. Returns results.
Mongo isn't looping in nodeJS with existing ids because the library isn't storing it in cache. Read the code base for the library.
Is there a way to generate an ID for a new document?
Something like
var newID = mongoose.Types.ObjectId();
// some random code that may involve db operations.
db.Model.create({_id: newID, otherProperties: {}})
When I write something like this, actual ID of the created document is always slightly larger than the newID. Is there anyway to use the newID exactly?
You should not create ID attribute for mongodb documents, It will automatically generate an ID attribute to all documents when we create them.
e.x
db.users.insert({name:'kasun',email:'kasun#gmail',address:'2street,colombo'})
this will crete an attribute called _id for the document of kasun.It is unique.Therefore don't set id attribute manually.
I am new to working with Azure table Storage but I have being able to put together the code below that successfully allows my query to accept filterQuery (string) specified by the user -- for ex: (Amount le 5000.00) -- and to retrieve all rows (entities) matching the criteria.
Dim sBuilder As New System.Text.StringBuilder
Dim query = MyBase.CreateQuery(Of cData)("CustomerData")
Dim userQuery = String.Format("(PartitionKey eq '{0}' and {1})", AppID, filterQuery)
sBuilder.AppendFormat(userQuery)
query = query.AddQueryOption("$filter", sBuilder.ToString).AsTableServiceQuery().Take(50)
Dim results As List(Of cData) = query.Execute.ToList
I should point out that this way of allowing the user to specify the filter string is key for me since I am using a generic class that has a dictionary inside of it in order to allow my caller to pass in any number of elements to store into a given entity. Therefore, this solution allows the user to drive how he wants his query to search by and my code does not have to 'know' anything about his custom fields.
Now I need to add pagination. My understanding is that the 'Execute' method I am using handles the pagination for you so if there are 7,000 records matching the criteria, my code will sit until all the entries are retrieved/returned. However, I want to instead allow my user to specify how many entities he wants returned at a time (max results) and allow him to then make subsequent calls using continuation tokens to get the next 'batch' of matching entities.
Any thoughts on how I can achieve this without losing my ability to allow the user to specify his search criteria in a simple string?
I think you can just do query.EndExecuteSegmented(query.BeginExecuteSegmented(...))
Check out the code for SmarxToDo: http://blog.smarx.com/posts/todo-list-app-using-asp-net-mvc-and-windows-azure-tables
You may want to implement your query using REST API (http://msdn.microsoft.com/en-us/library/dd179421.aspx). You will get XML response back from storage service which you can parse to create the collection of objects.