CODEWITHSUNDEEP
azure-cosmosdb
Thomas Segato
Thomas Segato

Reputation: 5265

Update another collection everytime a new document is inserted

I have two collections. As far as I can read (feel free to correct me if I am wrong) then you cannot join data between collections. So I am looking for the best approach to update one collection, every time documents are added to the other one. Lets take a simple sample:

Vessels:

[
    {
        "name": "vessel1",
        "id":1,
        "latestReportId":null,
        "latestReportName":null
    },
    {
        "name": "vessel2",
        "id":2,
        "latestReportId":null,
        "latestReportName":null
    }
]

Reports: Reports

[
    {
        "name": "Report1",
        "id":1
    },
    {
        "name": "Report1",
        "id":1
    }
]

My first thought was using a trigger, but I read that trigger can only apply on the current partition. What is the right approach to do this? I can't be the only one that want relations between collections :D

Upvotes: 1

Views: 1427

Answers (1)

Matias Quaranta
Matias Quaranta

Reputation: 15613

You could use the Cosmos DB Trigger in Azure Functions to sync both collections.

The Trigger can listen for changes in one collection and act (update/insert) data in another.

The full code sample and explanation is in this article, but basically you can create your trigger and tie it with an Output Binding like so:

public static async Task Run([CosmosDBTrigger(
    databaseName: "your-origin-database",
    collectionName: "your-origin-collection",
    ConnectionStringSetting = "your-origin-connectionstringsettings"
    ] IReadOnlyList<Document> documents,
    [CosmosDB("your-destination-database", 
    "your-destination-collection", 
    ConnectionStringSetting = "your-destination-connectionstringsettings")] IAsyncCollector<Document> saveDocuments,
    ILogger log)
{
    foreach (var doc in documents)
    {
        try
        {
            // do any transformation required to the original document
            await saveDocuments.AddAsync(doc); // You could also create a new document here based on information from the first one
        }
        catch(Exception ex)
        {
            log.LogError($"Failed to process document id {doc.Id}: {ex.Message}");
        }
    }
}

Upvotes: 4

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