Documentdb stored proc cross partition query

Question

I have a stored procedure which gives me a document count (count.js on github). I have partitioned my collection. Due to this, I now have to pass the partition key in as an option to run the stored procedure.

Can and how should I enable crosspartition queries in the stored procedure (ie, collection(EnableCrossPartitionQuery = true)) so that I don't have to specify the partition key?

Answer 1

There is no way to do fan-out stored procedure execution in DocumentDB. The run against a single partition. I ran into this dilemma when trying to switch to partitioned collections and had to make some adjustments. Here are some options:

1. Download a 1 for every record and sum/count them client-side

2. Rerun the stored procedure for each unique partition key. In my case, this was not as bad as it sounds since the partition key is a tenantID and I only have a dozen of those and only expect a few hundred max.

3. I'm not sure about this one since I haven't tried it with partitioned collections, but each query now returns the resource usage of the collection in the x-ms-resource-usage header. That header has a documentsSize sub-header. You could use that divided by the average size of your documents to get an approximate count. There may even be a count record in that header information by now.

4. Also, there is an x-ms-item-count header but I'm not sure how that behaves. If you send a query for all the records in the entire partitioned collection and set the max-item-count to 1, you'll only get back one record and it shouldn't cost you a lot in RUs, but I don't know how that header behaves. Does it return a 1 in that case? Or does it return the total number of documents all the pages of the query would eventually return if you bothered to request every page. A quick experiment should confirm this.