Ungrouped Results In Query Store

Erin Stellato explains why you might see two rows for the same query plan in Query Store’s run-time stats:

You can see that there are two rows for the same query_id and plan_id, but the count_executions is different, as are the avg_duration and avg_logical_io_reads values .  The data is not truly a duplicate.  This behavior occurs because the Query Store data is stored in memory before it is flushed to disk, and when you query the data SQL Server is pulling it from both locations (and doing a UNION ALL) and displaying it in the output.  If I waited a bit and ran the query again, the two rows for that interval would probably disappear – most likely because the in memory data had been flushed to disk.

Read the whole thing.

Related Posts

Workload Analysis with Query Store

Erin Stellato shows how you can mine the Query Store tables to learn more about your workload: The query text and plan are stored in two separate tables, sys.query_store_query_text and sys.query_store_plan, respectively.  The text is stored as a nvarchar(max) data type, and the plan is stored as varbinary(max).  This means that the data can be […]

Read More

Plan Forcing in Query Store

Erin Stellato continues a series on why you should be interested in Query Store: Before you go too crazy trying to stabilize performance with hundreds of forced plans, here are a couple things worth mentioning about plan forcing. 1. I think of plan forcing as a temporary solution. I do not view it as a […]

Read More

Categories

February 2018
MTWTFSS
« Jan Mar »
 1234
567891011
12131415161718
19202122232425
262728