Cosmos DB - Slow COUNT

Question

I am working on an existing Cosmos DB where the number of physical partitions is less than 100. Each contains around 30,000,000 documents. There is an indexing policy in place on "/*".

I'm just trying to get a total count from SQL API like so:

SELECT VALUE COUNT(1) FROM mycollection c

I have set EnableCrossPartitionQuery to true, and MaxDegreeOfParallelism to 100 (so as to at least cover the number of physical partitions AKA key ranges). The database is scaled to 50,000 RU. The query is running for HOURS. This does not make sense to me. An equivalent relational database would answer this question almost immediately. This is ridiculous.

What, if anything, can I change here? Am I doing something wrong?

Answer 1

Microsoft support ended up applying an update to the underlying instance. In this case, the update was in the development pipeline to be rolled out gradually. This instance got it earlier as a result of the support case. The update related to using indexes to service this type of query.