How Index Keys & Included Columns Work

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Follow up: KeyHashValue on DBCC PAGE

I did a little searching post webcast, and here’s what I found:

  • The “Expert Performance Indexing” book by Jason Strate and Grant Fritchey discusses KeyHashValue on page 46. They mention that KeyHashValue isn’t stored physically on the page, it is created when the page is placed in memory — and that one other place you may see KeyHashValue is when investigating deadlocks.
  •  Matt Lavery mentions KeyHashValue in his blog post discussion of DBCC PAGE, and in an aside mentions that this is used for resource locking (which matches up with the note that we might see this when chasing down deadlocks)

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Additional material, including tracing the latches in seeks and scans, is included in the extended version of this course.

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