----Original Message---- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Allen E. Elwood Sent: Tuesday, October 04, 2005 2:45 PM To: [email protected] Subject: RE: [U2] Fw: More U2 programming hints
> This is the way it was explained to me way back in '88. The > internal select > is slower on the whole file, but immediate in response. It > works the same > as LIST. If I list a file with 2,000,000 records I get > immediate response. > > If I want to process an entire file, then external select is slower on > response, i.e. I have to wait for 2 million records to be > selected before > processing begins, but is quicker in processing all records. > > The internal is slower due to the system having to stop what > it's doing, > find the next group, break out the individual ID's from that > group, and then > return it to the program - over and over again as it makes > it's way through > the file. Yes, well that *was* back in '88. :) Actually, I've no idea what UV does; there are many things which were implemented differently from Pr1me INFORMATION, or not at all. But IIRC, the issue above was addressed by pre-fetching the next group while processing the current one, so that processing and I/O overlap. With the right tuning, it would be significantly faster than processing after an external SELECT. -Keith ------- u2-users mailing list [email protected] To unsubscribe please visit http://listserver.u2ug.org/
