Hi, If I have three containers with the same partition key (say /projectid), will cosmos db put them into the same logical partition? What is the scope of the logical partition? Is it container scope only or it is database scope? Thanks for the help.

A logical partition is defined as the partition key value within a container. Your data will be stored in a minimum of three logical partitions * the number of partition key values across all three containers, even where the logical partition key values are the same. If you are new to Cosmos DB and horizontal partitioning/sharding, here is a Gist with some information to get you started. The second video is a good start. https://gist.github.com/markjbrown/114179b3d530abe0eaa25fb9ac54b609 PS: your scenario of having the same partition key in multiple containers is an anti-pattern. Generally speaking, when designing for Cosmos DB, an objective is to store data in the same container when it shares the same partition key and is frequently accessed together. If this fits your scenario. you should reconsider your design. Exceptions to this tend to include multi-tenant scenarios when trying to avoid noisy neighbor problem.

Will cosmos db put the data, which come from different containers but share the same partition key, to the same logical partition？

Accepted answer

Mark Brown - MSFT 2,766 Reputation points Microsoft Employee

2022-10-03T12:21:04.417+00:00

A logical partition is defined as the partition key value within a container. Your data will be stored in a minimum of three logical partitions * the number of partition key values across all three containers, even where the logical partition key values are the same. If you are new to Cosmos DB and horizontal partitioning/sharding, here is a Gist with some information to get you started. The second video is a good start. https://gist.github.com/markjbrown/114179b3d530abe0eaa25fb9ac54b609

PS: your scenario of having the same partition key in multiple containers is an anti-pattern. Generally speaking, when designing for Cosmos DB, an objective is to store data in the same container when it shares the same partition key and is frequently accessed together. If this fits your scenario. you should reconsider your design. Exceptions to this tend to include multi-tenant scenarios when trying to avoid noisy neighbor problem.
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Lavender Liu 21 Reputation points Microsoft Employee

2022-10-04T08:04:28.157+00:00

Hi Mark,

Thanks for your kind reply and explanation. It is a bit shame that our company already have a few systems running in production that have been migrated to Cosmos DB. But no one has the deep understanding of Cosmos DB. The overall design is still like the relational DB. This is also the reason why I decided to re-visit the videos that you have hosted for Azure Cosmos DB Live TV and take the DP420 learning path. The question that I asked above actually came from the video I watched, which is the one you suggest me to watch.

I do enjoy the video made by Thomas and Deborah about the best practices of Cosmos DB (https://www.youtube.com/watch?v=bQBeTeYUrR8&list=RDLVutdxvAhIlcY&index=5). I would like to know if there is any more resources or real world examples to talk about the best practices especially for mixing entity types?

Finally, I have one more quick question. We are eager to use analytical store for Cosmos DB Mongo API. Since months ago Rodrigo mentioned (https://feedback.azure.com/d365community/idea/3703bb6d-381e-ed11-a81b-6045bd8606d4) that the function for enabling analytical store on existing collections (Mongo API) will be announced for preview, can we assume we will get this function for preview in Q4 2022?

Thanks for your help.

Mark Brown - MSFT 2,766 Reputation points Microsoft Employee

2022-10-04T23:27:33.25+00:00

Aside from the GitHub Gist I shared there is a playlist of modeling and partitioning videos here. However, most of these are the same content. This one on a book store however is a bit different. I apologize we don't have lots of additional best practices or patterns in this area. General application of the patterns we do suggest should work in most cases. However, it is important to try different things and measure to ensure the best efficiency and performance.

Synapse Link support for existing MongoDB collections is definitely on the roadmap but I do not have any more information. I will forward this thread on to Rodrigo. Not sure he can comment as we generally try not to disclose releases before they happen :) but will forward either way.

Lavender Liu 21 Reputation points Microsoft Employee

2022-10-05T08:19:17.867+00:00

Thank you. Your replies and advice are much appreciated.

Rodrigo Souza 1 Reputation point Microsoft Employee

2022-10-06T00:47:33.89+00:00

SL for MongoDB is in roadmap and the estimated time of arrival is December of this year. This is an estimate, not a firm deadline. Tks!

Lavender Liu 21 Reputation points Microsoft Employee

2022-10-06T23:32:11.363+00:00

Thanks. Looking forward to it.
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Will cosmos db put the data, which come from different containers but share the same partition key, to the same logical partition？

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