Controls how data is spread out. Azure Cosmos DB puts items whose values match into one logical partition, and Azure Table storage stores rows sharing a PartitionKey side by side.
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Terms in this definition
- Cosmos DB
NoSQL database distributed globally, offering writes in multiple regions, automatic indexing and latency below 10 ms.
- VALUES
Returns in DAX the distinct column values, or table rows, still visible after filters are applied, sometimes with an extra blank entry. CALCULATE often takes the result as a table filter.
- MATCH
Used in WHERE when querying SQL Graph, it describes how to walk from node to node through edge tables, with patterns written like p1-(f1)->p2.
- Logical partition
Every Cosmos DB item with one particular partition key value. Transactions cannot cross it, and it is capped at 20 GB.
- Azure Table Storage
Holds structured NoSQL records without a fixed schema, using keys and attributes; think device details, contact lists or user records. It now sits within the Azure Cosmos DB family, where Azure Cosmos DB for Table is the premium step up.
Related terms
- Cross-partition query
Also known as a fan-out query: in Azure Cosmos DB, a query with no partition key filter, which therefore has to visit each physical partition in turn. Each partition visited costs roughly 2.5 RU or more, so these queries consume more request units.
- Hot partition
A Cosmos DB physical partition that handles far more than its share of traffic because the partition key is unevenly distributed. The result is 429 throttling and throughput (RU/s) going unused elsewhere.
- In-partition query
Filtering a Cosmos DB query on one exact partition key value means only the matching physical partition is asked, which costs less than fanning out across partitions.
- Lease container
Holds the lease documents through which the Cosmos DB change feed processor records how far each partition key range has got and shares work out between instances.
- Point read
Retrieving one Cosmos DB item straight from its partition key and id via the REST API or an SDK. It is the lowest-cost read, around 1 RU per 1 KB, and a query with an id filter doesn't qualify.