Summary: A deep dive into SQL Server parallelism, and a potential performance problem with parallel plans that use TOP.
Thursday 3 May 2012
Parallel Execution Plans Suck
Tuesday 1 May 2012
Query Optimizer Deep Dive - Part 4
This is the final part in a series of posts based on the content of the Query Optimizer Deep Dive presentations I have given over the last month or so at the Auckland SQL Users’ Group, and SQL Saturday events in Wellington, New Zealand and Adelaide, Australia.
Links to other parts of this series: Part 1 Part 2 Part 3
Beating the Optimizer
Our AdventureWorks test query produces an optimized physical execution plan that is quite different from the logical form of the query.
The estimated cost of the execution plan shown below is 0.0295 units.
Since we know the database schema very well, we might wonder why the optimizer did not choose to use the unique nonclustered index on Name in the Product table to filter rows based on the LIKE predicate.
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