Query Store Isn’t A Forensics Engine

Grant Fritchey shows that Query Store has a limited capability of finding “ill-behaving” queries at a point in time:

Here’s a great question I received: We had a problem at 9:02 AM this morning, but we’re not sure what happened. Can Query Store tell us?

My first blush response is, no. Not really. Query Store keeps aggregate performance metrics about the queries on the database where Query Store is enabled. Aggregation means that we can’t tell you what happened with an individual call at 9:02 AM…

Well, not entirely true.

Query Store isn’t a total solution for “Why was the system slow at XX:XX?” types of questions.  This does not diminish its value as long as you do not try to treat it as your only monitoring solution.

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Good Query Store Default Settings

Erin Stellato gives us a starting point for good values for Query Store settings: QUERY_CAPTURE_MODE The default value for SQL Server 2016 and SQL Server 2017 is ALL.  For Azure SQL Database, the default value is AUTO. With AUTO, queries that are insignificant from a resource utilization perspective, or executed infrequently, are not captured.  If […]

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Getting Wait Stats From The Query Store

Erin Stellato shows how to retrieve wait stats per query from Query Store: In SQL Server 2016 a new DMV is exposed, sys.dm_exec_session_wait_stats, which provides information about waits for an existing, active session. If you know the session_id, you can track waits for a query when it starts and when it completes (snapshot the information at […]

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