Querying the Execution Plan for Subtree Cost - Take 2

A few weeks ago I shared a query for probing the execution plan for the Estimated Subtree Cost value.

That query was rather simple but it got the job done. In that post I also explained how, although there are several ways of finding missing index suggestions, they were not always very helpful. After posting I was thinking that it would be helpful to combine the two, or at least display the results so that it is easy to determine which execution plans include missing index warnings.

Querying the Execution Plan XML for Subtree Cost

There are quite a lot of great tools and queries available to the DBA that aid in troubleshooting and performance tuning. The list is incredibly long, but I mainly use RedGate's SQL Monitor (which has come on in the last 5 years in leaps and bounds), Glenn Berry's DMV queries, Adam Machanic's sp_whoisactive and Brent Ozar Unlimited's sp_Blitz suite (predominantly sp_Blitz and sp_BlitzIndex). In writing this, I see that Brent Ozar has expanded his offering, so it looks like I have a weekend project ahead of me!

Tracking Query Plan Changes

I was reading a blog post from Brent Ozar (SQL Server Query Store), which detailed Microsoft's announced future feature in SQL Server that aims to store a history of cached execution plans. The main purpose, it seems, of such a feature is to aid in performance troubleshooting and tuning. If something has changed recently and a query or store procedure begins behaving badly, there will be another tool in the DBA toolbelt to aid in finding what happened. Beyond that I'll let others explain it further.