Quote:
Originally Posted by pootle flump
Where on earth do you get the idea that he does?
|
Here's a quote from the paper:
Quote:
|
Originally Posted by Itzik Ben Gan et al.
As you can see, the algorithmic complexity of this plan is N^2. With a large number of rows per employee, you get enormous numbers. For example, with 5 employees and 100,000 rows per employee, you get 25,000,250,000 rows scanned. In terms of run time this query would run over an hour. With a higher number of rows per employee, the performance degrdation is not linear, rather N^2. For example, having a single partition and 10,000,000 rows, this query would run for about a year!
|
Quote:
Originally Posted by pootle flump
I really wouldn't dismiss Itzik Ben Gan's writings too lightly. He is easily up there in the top 10 of SQL Server gurus, and very possibly the very top T-SQL expert on the planet.
|
I'm not dismissing Mr. Ben Gan's expertise, far from it. I'm just saying that reading twice the rows does not necessarily take twice the time. The number of rows read may be growing exponentially as data accumulate, but query run time does not have to, and in my experience often does not.