QueryRuntimeStatistics (Diagnostic Log)
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Category: Maintenance & Security
Summary: Logs query operations against the account for query performance analysis.
Overview
QueryRuntimeStatistics is a diagnostic log table that logs query operations executed against an Azure Cosmos DB for NoSQL account, including details useful for analyzing query text, RU charge, and execution performance. It is commonly used alongside query metrics to identify expensive or inefficient queries that may benefit from indexing policy or query rewrites. In Log Analytics, this table is exposed under the name CDBQueryRuntimeStatistics.
Example (KQL): Find the most expensive queries and their text
CDBDataPlaneRequests
| where todouble(RequestCharge) > 10.0
| project ActivityId, RequestCharge
| join kind=inner (
CDBQueryRuntimeStatistics
| project ActivityId, QueryText
) on $left.ActivityId == $right.ActivityId
| order by RequestCharge desc
| limit 100
This query joins CDBDataPlaneRequests (RU charge per request) with CDBQueryRuntimeStatistics (the query text) on the shared ActivityId, filters for requests costing more than 10 RUs, and returns the 100 most expensive queries together with their full query text — a common first step when troubleshooting unexpectedly high RU consumption.
More Info & Links
DP-420 Style Practice Questions
Q1. What does the QueryRuntimeStatistics diagnostic log table capture?
- A. Details of query operations run against an Azure Cosmos DB for NoSQL account
- B. Per-partition storage size in KB
- C. Control-plane operations like adding a region
- D. Change feed consumer lag
Q2. Why would you review QueryRuntimeStatistics during optimization?
- A. To identify expensive or inefficient queries that might need indexing policy changes or rewrites
- B. To determine which partition key value has the most storage
- C. To check which regions accept writes
- D. To view the account's backup retention window
Answer Key
Answers are listed at the very end so you can attempt the questions first.
- Q1 (QueryRuntimeStatistics (Diagnostic Log)): A. Details of query operations run against an Azure Cosmos DB for NoSQL account — QueryRuntimeStatistics logs details about queries executed against the account, useful for query performance analysis.
- Q2 (QueryRuntimeStatistics (Diagnostic Log)): A. To identify expensive or inefficient queries that might need indexing policy changes or rewrites — This table helps surface costly or slow queries so their indexing policy or query text can be optimized.
DP-420: Designing and Implementing Cloud-Native Applications Using Microsoft Azure Cosmos DB — term detail page
