Simple CosmosDb query high RU

0
votes

I am evaluating Cosmos Db for a project and working through the documentation. I have created a sample collection following the documentation on this page https://docs.microsoft.com/en-us/azure/cosmos-db/sql-query-getting-started. When I run the first query on this page in the local emulator I get the following results:

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Why is the Request Charge 2.89 RUs? From all of the documentation I have read this should be 1 RU. The collection is partitioned on the id field and is auto indexed and Cross Partition Queries are enabled. I have event tried putting both items in the same partition and I get the same results.

1
azure-cosmosdb
You can also try to pass the partition key so it will limit the query search and lower the RU/s consumition. - Kiril1512

1 Answers

1
votes

1 RU is the cost of a Point-Read operation, not a query. Reference: https://docs.microsoft.com/azure/cosmos-db/request-units:

The cost to read a 1 KB item is 1 Request Unit (or 1 RU).

Also there:

Query patterns: The complexity of a query affects how many RUs are consumed for an operation. Factors that affect the cost of query operations include

If you want to read a single document, and you know the id and partition key, just do a point operation, it will always be cheaper than a query with the id="something" query. If you don't know the partition key, then yes, you need a cross partition query, because you don't know on which partition key is stored and there could be multiple documents with the same id (as long as their partition keys are different, see https://docs.microsoft.com/azure/cosmos-db/partitioning-overview).

You can use any of the available SDKs or work with the REST API.