Function Invertability for SARGability

My good friend Simon Sabin used the term ‘invertability’ on a Connect item he logged today. Essentially, Simon’s noticed that there are lots of people that use year(someDate), but that the system doesn’t understand that this function doesn’t affect the order of the items in the index. month(someDate) does, but if you’re already using year(someDate), … Continue reading Function Invertability for SARGability

Probe Residual when you have a Hash Match – a hidden cost in execution plans

No, this post has nothing to do with airport security, and nothing to do with marijuana. Being honest, this post is only half about Hash Matches and Probe Residuals. It’s more about the types of predicates you can see mentioned in a SQL Server Execution Plan (or Query Plan, but I prefer to call them … Continue reading Probe Residual when you have a Hash Match – a hidden cost in execution plans

How many people will be with you during 24HOP?

In less than a week, SQLPASS hosts another 24 Hours of PASS event, this time with an array of 24 female speakers (in honour of this month being Women’s History Month). Interestingly, the committee has had a few people ask if there are rules about how the event can be viewed, such as “How many … Continue reading How many people will be with you during 24HOP?

The blocking nature of aggregates

I wrote a post recently about how query tuning isn’t just about how quickly the query runs – that if you have something (such as SSIS) that is consuming your data (and probably introducing a bottleneck), then it might be more important to have a query which focuses on getting the first bit of data … Continue reading The blocking nature of aggregates