I have custom page and it has a CbQ webpart alone, it actually performs a query against a single list which has only 800 items with 15 columns but it takes 8secs to load. I suspect a slowness in SQL, how I can conclude that it is an issue with the SQL. Sometimes I could see the long running queries in the ULS log.
The filter columns are used in the CbQ webpart are not indexed, will it impact the overall performance?
If so, howmany columns can be used for Indexing that should not affect the performance again? also, how can I eusure that Index is created for that site column?