Cardinality Estimator understading

Copper Contributor

I have a query that i am running from the query analyser, there are no trace flags enabled in it. When do properties of the select in the query plan I see following

anoopdba_0-1682696348082.png

My database is at compatibility lever 150, so why i am seeing this? Is it normal ?

3 Replies

@anoopdba 

 

The cardinality estimation version can vary, and a lower value doesn't automatically imply something is wrong.

 

Read the following article thoroughly as it covers:

 

  • Some of the scenarios where the cardinality estimation can run into issues (probably the most useful part to read);
  • How to monitor cardinality and make sense of the results;
  • How to force cardinality (where appropriate to do so.)

 

 

Cheers,

Lain

@LainRobertson Thanks for your help. I have gone through the article.

The query i am looking at is performing poorly and i am not sure why it is using an old cardinality estimator even though my database is at latest CE.

@anoopdba 

 

The article outlines multiple reasons in the second bullet point list near the top of the article.

 

Cheers,

Lain