Why are queries getting dropped from query store?

Question

I see sometimes that queries are dropped from the query store. But I don't know why. The query store disk-space is not full and the query is far from the stale query treshold.

What I experience is that a query that I know has been executed has no history of getting executed in query store.

I will run this query to get the query_id:

SELECT   t.query_sql_text, q.query_id, object_name(q.object_id) AS parent_object, q.query_text_id, q.count_compiles
    FROM sys.query_store_query_text t JOIN sys.query_store_query q ON t.query_text_id = q.query_text_id 
WHERE  t.query_sql_text LIKE  N'%part_of_query%'

And then I use the query_id in 'Tracked queries'.

But, sometimes, if I later in the day want to look at this query and run the above query again I get a new query_id and there is no trace of the old query_id. This can even impact 'Total resource consumption'. If the new query_id was created 11:00 and consumed a lot of resources, then it will look like there was a sudden increase in resource usage at 11:00.

The queries I often look at involve a temporary table, which means that there is a batch_sql_handle stored with the query_id. I know that database_id is part of this and that a failover on an Always On AG would cause a similar situation. ref: https://milossql.wordpress.com/2019/10/21/dude-wheres-my-forced-plan-part-1/ I have been trying to find more information about what the batch_sql_handle is based on and how the auto cleanup is working, but have not found anything that helps me.

Size Based Cleanup Mode is set to Auto

Answer 1

After setting up an extended events session looking at query store cleanup I saw my query_id in an event: query_store_size_retention_query_deleted

So my queries are getting dropped to avoid reacing size limit. flush_interval_settings was set to 1 min, which probably contributed to this.