How SQL Server 2019 Helps You Find Queries That Have Missing Index Requests

bigtime

In the quest for me trying to get people to upgrade to a not-old-and-busted version of SQL Server, this is one that I talk about a lot because it really helps folks who don’t have all the time in the world to tune queries and indexes.

Here’s a quick helper query to get you started:

SELECT TOP (50)
    query_text = 
        SUBSTRING
        (
            st.text,
            qs.statement_start_offset / 2 + 1,
            CASE qs.statement_start_offset
                 WHEN -1 
                 THEN DATALENGTH(st.text)
                 ELSE qs.statement_end_offset
            END - qs.statement_start_offset / 2 + 1
        ),
    qp.query_plan,
    qs.creation_time,
    qs.last_execution_time,
    qs.execution_count,
    qs.max_worker_time,
    avg_worker_time = 
        (qs.total_worker_time / qs.execution_count),
    qs.max_grant_kb,
    qs.max_used_grant_kb,
    qs.total_spills
FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) AS st
CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) AS qp
CROSS APPLY
(
    SELECT TOP (1)
        gqs.*
    FROM sys.dm_db_missing_index_group_stats_query AS gqs
    WHERE qs.query_hash = gqs.query_hash
    AND   qs.query_plan_hash = gqs.query_plan_hash
    AND   qs.sql_handle = gqs.last_sql_handle
    ORDER BY
        gqs.last_user_seek DESC,
        gqs.last_user_scan DESC
) AS gqs
ORDER BY qs.max_worker_time DESC
OPTION(RECOMPILE);

This should help you find queries that use a lot of CPU and might could oughtta use an index.

Note that this script does not assemble the missing index definition for you. That stuff is all readily available in the query plans that get returned here, and of course the missing index feature has many caveats and limitations to it.

You should, as often as possible, execute the query and collect the actual execution plan to see where the time is spent before adding anything in.

Thanks for reading!

Going Further

If this is the kind of SQL Server stuff you love learning about, you’ll love my training. I’m offering a 25% discount to my blog readers if you click from here. I’m also available for consulting if you just don’t have time for that and need to solve performance problems quickly.