Count rows within partition in Azure table storage
I've seen various questions around SO about how to get the total row count of an Azure storage table, but I want to know how to get the number of rows within a single partition.
How can I do this while loading a minimal amount of entity data into memory?
Answer
As you may already know that there's no Count like functionality available in Azure Tables. In order to get the total number of entities (rows) in a Partition (or a Table), you have to fetch all entities.
You can reduce the response payload by using a technique called Query Projection. A query projection allows you to specify the list of entity attributes (columns) that you want table service to return. Since you're only interested in total count of entities, I would recommend that you only fetch PartitionKey back. You may find this blog post helpful for understanding about Query Projection: https://blogs.msdn.microsoft.com/windowsazurestorage/2011/09/15/windows-azure-tables-introducing-upsert-and-query-projection/.