Handling LINQ "Count" queries as IDocumentQuery

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Horsing around the CosmosDB .NET SDK, I found an intriguing issue. I wanted to use the SDK LINQ support for the following query:

SELECT VALUE COUNT(1) FROM c WHERE <predicate>

Well, immediately after writing the LINQ query, I realized there might be no way to handle such queries as document queries. However, since document queries allow you to capture query metrics and unblock a thread between pages of results, I strongly prefer it. Here's the code:

client.CreateDocumentQuery<TEntity>.Where(<predicate>).Count()

Even though I understand that the result type of Count() isn't IQueryable, is there a way to handle "count" queries as document queries?

azure-cosmosdb linq
1 Answers

Of course there is a way to do that.

There is a CountAsync extension built into the SDK.

Simply construct your IQueryable and use .CountAsync() when you are ready to get the count.

Keep in mind however that there will be no metric collection as the result is aggregated in the SDK.

If you really need metrics then you can use the usual DocumentQuery created from SQL rather than LINQ and the while.HasMoreResults, ExecuteNextAsync logic and capture the metrics from the paginated result, per iteration.

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