Triggers

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

Triggers are pieces of application logic that can be 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. It is a user settable property. It is the unique name used to identify the trigger. The ID must not exceed 255 characters.
body Required. It is a user settable property. It is the body of the trigger.
triggerOperation Required. It is the type of operation that invokes the trigger. The acceptable values are: All, Insert, Replace and Delete.
triggerType Required. This specifies when the trigger is fired. The acceptable values are: Pre and Post. Pre triggers fire before an operation while Post triggers after an operation.
_rid It 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 It is a system generated property. It specifies the last updated timestamp of the resource. The value is a timestamp.
_self It is a system generated property. It is the uniquely addressable URI for the resource.
_etag It 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.

See Also