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Message Posted: Fri, 29 Jan 2010 @ 16:20:00 GMT

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Subj:   Re: Workaround to avoid product join
From:   Dieter Noeth

Victor Sokovin wrote:

  Product join has the best performance? I guess we all are learning something new here every day.  

I wondered, too.

It's not the product join per se, but the huge intermediate spool created by it. An average range of just 10 minutes already results in 1,500,000,000 rows (150,000,000 * 10).

I compared both queries on about 10 mio random rows with 3 products and approx. 12 minutes average range and there was a 1:40 difference in runtime and CPU usage.

  A lot depends on the data, of course. Perhaps the pre-aggregation suggested by Dieter did not reduce the volumes much in your particular case? The skew is another thing to check, as always.  

Yep, would be nice to get some more info about the actual data.


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