Read Azure DocumentDB document that might not exist

Question

I can query a single document from the Azure DocumentDB like this:

var response = await client.ReadDocumentAsync( documentUri );

If the document does not exist, this will throw a DocumentClientException. In my program I have a situation where the document may or may not exist. Is there any way to query for the document without using try-catch and without doing two round trips to the server, first to query for the document and second to retrieve the document should it exist?

Answer 1

Sadly there is no other way, either you handle the exception or you make 2 calls, if you pick the second path, here is one performance-driven way of checking for document existence:

public bool ExistsDocument(string id)
{
    var client = new DocumentClient(DatabaseUri, DatabaseKey);
    var collectionUri = UriFactory.CreateDocumentCollectionUri("dbName", "collectioName");
    var query = client.CreateDocumentQuery<Microsoft.Azure.Documents.Document>(collectionUri, new FeedOptions() { MaxItemCount = 1 });
    return query.Where(x => x.Id == id).Select(x=>x.Id).AsEnumerable().Any(); //using Linq
}

The client should be shared among all your DB-accesing methods, but I created it there to have a auto-suficient example.

The new FeedOptions () {MaxItemCount = 1} will make sure the query will be optimized for 1 result (we don't really need more).

The Select(x=>x.Id) will make sure no other data is returned, if you don't specify it and the document exists, it will query and return all it's info.