Partial Document Update Samples with Cosmos DB REST Operation

Overview :

In last November 2021, Cosmos DB team has announced support for patching documents with SQL API which was the top requested features in the user voice. This is a useful and long-awaited feature among users. Prior to this announcement the only way to change the stored document was to completely replace it. Users will be able to perform Partial updates with all the Cosmos DB SDKs ( JAVA, . Net , JS ) and also Cosmos DB REST API.

Use Case:

Let’s look at a scenario of a dashboard application where user need to display the System and it’s features. User has decided to use Cosmos DB as a database to store the data of a System and it’s features. A sample document would look as follows.

{
    "ApplicationId": "App-01",
    "ApplicationName": "New Cosmos Client",
    "Description": "This shows the users and interactions",
    "IsDraft": 0,
    "IsSaved": 1,
    "Features": [
        {
            "SystemID": 1,
            "Features": [
                {
                    "FeatureID": 4,
                    "FeatureName": "Patch",
                    "IsActive": false
                },
                {
                    "FeatureID": 35,
                    "FeatureName": "Feature-a-2",
                    "IsActive": false
                },
                {
                    "FeatureID": 36,
                    "FeatureName": "test-feature-a-3",
                    "IsActive": true
                } 
            ]
        }
    ],
    "id": "af3dfd7a-b7e9-4467-a2ca-9c6be7ad5b9f",
    "_rid": "S1xQAKKOTBABAAAAAAAAAA==",
    "_self": "dbs/S1xQAA==/colls/S1xQAKKOTBA=/docs/S1xQAKKOTBABAAAAAAAAAA==/",
    "_etag": "\"31003582-0000-0700-0000-6213cb6b0000\"",
    "_attachments": "attachments/",
    "_ts": 1645464427
}

Let’s look at some of the scenarios where user needs to perform patch operations.

Patch Scenario 1:  Add a new record (JSON object) under Features parent array 

JSON object to Add:

{
       "SystemID": 2,
       "Features": [
       {
          "FeatureID": 1,
          "FeatureName": "Reports",
          "IsActive": false
       }
     ]
 }

You can refer my previous blog on How to setup Rest Operations with Postman. Once you’ve configured the setup with the underlying database and container. Here we need to insert a new Object within the Features array, certainly we can leverage the Single Add Operation. And the sample request Body will be like,

Patch Url : https://account/dbs/dbName/colls/Patch/docs/id of the document and the header “x-ms-documentdb-partitionkey” is set to the partition key value which is the “ApplicationId“App-01”. And we need to specify the path as “/Features/-“

Add new JSON object under Features Array

On a successful response, in the backend you will see that a new Object that is shown above will be added to the Features array.

Patch Scenario 2:  Update the Application Description in the root Object to “Testing Patch with REST API”

Patch Scenario 3:  Update only a specific Feature object in array for a given Features parent object like FeatureName . Let’s assume if we need to update the Object at the 0th index and then update the First Features Object,

Patch Scenario 4 : Perform all the above operations as a single request

Since Partial document update supports up to 10 operations in a single request, all the above operations can be merged. User needs to combine all the operations as one as below,

{
   "operations":[
     {
         "op":"replace",
         "path":"/Features/0/Features/0/FeatureName",
         "value":"Patch Testing"
    },
    {
         "op":"set",
         "path":"/Description",
         "value":"Testing Patch with REST API"
    },
    {
    "op":"add",
    "path":"/Features/-",
    "value":{
       "SystemID": 2,
       "Features": [
           {
               "FeatureID": 1,
               "FeatureName": "Reports",
               "IsActive": false
           }
       ]
    }
   }
 ]
}

Hope these samples help you to perform different operations at different path using Cosmos Rest API. Cheers!

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