I have the same test database restored to separate Virtual Machines with SQL2005 and SQL2008 installed. Indexes have been rebuilt and statistics updated. I boot either VM, open Management Studio, set STATISTICS TIME and IO on, and run a simple query that
groups and sums rows in a table containing 2.3 million rows.
Scan count 1, logical reads 111522, physical reads 0, read-ahead reads 111522
Scan count 1, logical reads 111522, physical reads 2836, read-ahead reads 111522
How did SQL2005 return the same 6200 row result set without performing any physical reads? Did the way these statistics were generated alter between the two versions?
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