Triggers

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Azure Cosmos DB is a a globally distributed multi-model databases that supports the document, graph, and key-value data models. The content in this section is for managing trigger resources using the DocumentDB API via REST.

Triggers are pieces of application logic that can executed before (pre-triggers) and after (post-triggers) creation, deletion, and replacement of a document. Triggers are written in JavaScript. Both pre and post triggers do no take parameters. Like stored procedures, triggers live within the confines of a collection, thus confining the application logic to the collection.

Similar to stored procedures, the triggers resource has a fixed schema. The body property contains the application logic. The following example illustrates the JSON construct of a trigger.

{  
"id":"PostTrigger-UpdateMetaAll",  
"body": "  
function updateMetadata() {  
        var context = getContext();  
        var collection = context.getCollection();  
        var response = context.getResponse();  
        var createdDocument = response.getBody();  

        // query for metadata document  
        var filterQuery = 'SELECT * FROM root r WHERE r.id = "_metadata"';  
        var accept = collection.queryDocuments(collection.getSelfLink(), filterQuery,  
            updateMetadataCallback);  
        if(!accept) throw "Unable to update metadata, abort";  

        function updateMetadataCallback(err, documents, responseOptions) {  
            if(err) throw new Error("Error" + err.message);  
                     if(documents.length != 1) throw 'Unable to find metadata document';  
                     var metadataDocument = documents[0];  

                     // update metadata  
                     metadataDocument.createdDocuments += 1;  
                     metadataDocument.createdNames += " " + createdDocument.id;  
                     var accept = collection.replaceDocument(metadataDocument._self,  
                           metadataDocument, function(err, docReplaced) {  
                                  if(err) throw "Unable to update metadata, abort";  
                           });  
                     if(!accept) throw "Unable to update metadata, abort";  
                     return;                      
        }  
}  
",  
"_rid":"hLEEAI1YjgcBAAAAAAAAgA==",  
"_ts":1408058682,  
"_self":"dbs\/hLEEAA==\/colls\/hLEEAI1Yjgc=\/udfs\/hLEEAI1YjgcBAAAAAAAAgA==\/",  
"_etag":"00004100-0000-0000-0000-53ed453a0000"  
}

Property	Description
id	Required. This is a user settable property. It is the unique name used to identify the trigger. The id must not exceed 255 characters.
body	Required. This is a user settable property. This is the body of the trigger.
triggerOperation	Required. This is the type of operation that will invoke the trigger. The acceptable values are: All, Insert, Replace and Delete.
triggerType	Required. This specifies when the trigger will be fired. The acceptable values are: Pre and Post. Pre triggers fire before an operation while Post triggers after an operation.
_rid	This is a system generated property. The resource ID (_rid) is a unique identifier that is also hierarchical per the resource stack on the resource model. It is used internally for placement and navigation of the trigger resource.
_ts	This is a system generated property. It specifies the last updated timestamp of the resource. The value is a timestamp.
_self	This is a system generated property. It is the uniquely addressable URI for the resource.
_etag	This is a system generated property that specifies the resource etag required for optimistic concurrency control.

Tasks

You can do the following with triggers:

For information on how UDFs work including invoking a trigger, see Azure Cosmos DB programming: Stored procedures, triggers, and UDFs.

Triggers

Tasks

See Also