What are you using for the row key? --- Jim Kellerman, Senior Engineer; Powerset
> -----Original Message----- > From: Zhou Wei [mailto:[EMAIL PROTECTED] > Sent: Tuesday, April 29, 2008 9:02 AM > To: [email protected] > Subject: Re: obtain the maximum value of the row id of a table > > Bryan Duxbury wrote: > > No, we can't scan in reverse. I don't think it's possible to do so > > with the components we have today - there's no previous method on > > mapfile, only next. Out of curiosity, hat's the use case > for getting > > the last N records in the table? > > > > -Bryan > > > The use cases come from a standard transactional web > application benchmark TPC-W, which models an online bookshop. > > Use cases: > 1) obtain the latest order of a specified user As new order > is inserted at the end of table, it is better to start scan > in reverse direction. > > 2) obtain the top 50 books which sells best recently. > The calculation is based on the information of 3333 most > recent orders. > Again, better to start scan from the end of table. > > - Zhou > > On Apr 29, 2008, at 8:08 AM, Zhou Wei wrote: > > > >> > >>> Hm, tricky. You don't have the scan the whole table - > just the last > >>> region. You can find out what the start key of the last > region is by > >>> using HTable#getStartKeys. If this isn't an acceptable > solution, we > >>> might be able to think up a way to get the last real row > of a table > >>> more efficiently. > >> Actually, I need to obtain the 3333 rows starting from the > last row > >> rather than the first row. > >> So I wonder is it possible to obtain a scanner that scan in the > >> reverse direction. > >> I.e. Starting from the last row to the first row. > >> > >> Zhou > >>> > >>> -Bryan > >>> > >>> On Apr 28, 2008, at 7:53 PM, Zhou Wei wrote: > >>> > >>>> Hi > >>>> > >>>> I want to find out the maximum value of the row id of a table. > >>>> Is there a simple and efficient way to do this without > scan through > >>>> the whole table starting from the first row? > >>>> > >>>> Thanks. > >>>> > >>>> Zhou > >>> > >>> > >>> > >> > > > > > > > > > No virus found in this incoming message. > Checked by AVG. > Version: 7.5.524 / Virus Database: 269.23.6/1403 - Release > Date: 4/29/2008 7:26 AM > > No virus found in this outgoing message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.23.6/1403 - Release Date: 4/29/2008 7:26 AM
