CosmosDB - Setting a Partition Key

Question

Can anyone tell me how to programmatically set a partition key on cosmosdb?

If you have an example (don't mind which language) id be really grateful.

Thanks,
Paul.

Answer 1

Hi @Anonymous Thank you for posting your question on Microsoft Q&A and for using Azure Services.

As per my understanding you are trying to automatically set a partition key on Cosmos DB. Please let me know if my understanding is not correct.

Programmatically setting partition KEY in Azure Cosmos DB is not yet available. You can choose the partition key for your container but cannot automatically set up partition key.
Azure Cosmos DB automatically can create new physical partitions by splitting existing ones. see Partitioning and horizontal scaling in Azure Cosmos DB

Regards,
Oury

Answer 2

Hi Oury,
thanks for the answer - that's not good.

I create a lot of data in my app (about 20-25 gb) which is the limit for the partition keys, how would you address needing more partition keys?

Thanks,
Paul.

Answer 3

I think it's a bit too late if a partition hits the actual limit.

It depends on your use cases. If it's a write-heavy, read-heavy scenario, you can use a hierarchical partition key on two or more properties. If you don't care about reading the data (for example you have a change feed processor or a connector to Kafka), you can use a synthetic partition key composed of multiple fields and even add a random value at the end, so there are as many partitions are documents (which is fine).

In both cases, you need to create a new container and migrate. The existing partitions are full, and you can't change the partition key path. You can do it with a FeedIterator on the change feed with the pull model. Or you can find migration tools, I think Alpaqa offers one.

Technically you can even leave the data where it is and store new data in a new container, but it always depends on how you use them.