tag:blogger.com,1999:blog-3635447662505002071.post1775257263601456166..comments2022-03-31T03:30:53.887+01:00Comments on Database Science: Datetimes and Intsdbsciencehttp://www.blogger.com/profile/05472838753270367869noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-3635447662505002071.post-30926329843214223622008-09-19T20:45:00.000+01:002008-09-19T20:45:00.000+01:00When I was testing timestamps vs. datetimes I foun...When I was testing timestamps vs. datetimes I found timestamps to take about 33 seconds compared to 21 seconds for datetimes when the data didn't fit into memory. I found it almost unbelievable that timestamps were slow enough to impact what should have been an io bound process. I should have made this clearer. <BR/><BR/>But if your data does fit into memory, then I agree, this test isn't realistic. Are there a lot of people out there for whom this is true? How big are your databases? <BR/><BR/>As for me, I typically deal with 100s of gigs or terabytes of data. This means the bottleneck in the systems I deal with is usually io. Not always, with MySQL concurrency is often a problem as well, but when I profile the worst performing queries the bottleneck is rarely CPU. <BR/><BR/>So, to tune these systems, if the performance difference between two approaches is insignificant (such as 2%) when compared to the io component of that query I generally don't worry about. This is basic bottleneck performance tuning, where one goes after the largest bottlenecks. Stated differently, I worry about how to speed up the 98% of the query. <BR/><BR/>All of this means, for me, a good test includes the impact of io.dbsciencehttps://www.blogger.com/profile/05472838753270367869noreply@blogger.comtag:blogger.com,1999:blog-3635447662505002071.post-160179728127815162008-09-19T05:47:00.000+01:002008-09-19T05:47:00.000+01:00You're really only testing your disk subsystem thi...You're really only testing your disk subsystem this way...<BR/><BR/>No one runs DBs off disk anymore anyway :)<BR/><BR/>All our data fits in memory.burtonatorhttps://www.blogger.com/profile/08049781702053733725noreply@blogger.com