but if you do not know how many results you have then that can happen using any approach...
-igor On Thu, Apr 12, 2012 at 2:36 AM, Michal Wegrzyn <michal.wegr...@onior.com> wrote: > That's the solution which I have used for the case, where count is not > possible. > It has only one slight disadvantage - if count == n*pageSize then the last > page will be blank. > > Best regards, > Michal Wegrzyn > >> -----Original Message----- >> From: Igor Vaynberg [mailto:igor.vaynb...@gmail.com] >> Sent: Thursday, April 12, 2012 6:06 >> To: users@wicket.apache.org >> Subject: Re: IDataProvider#size() >> >> why not just fake the size to current page+1? that way you always have >> a "next" link and once you receive the current page you should know if >> you have more or not so you dont have to add the one on the last >> page.... >> >> -igor >> >> On Wed, Apr 11, 2012 at 6:59 PM, Dan Retzlaff <dretzl...@gmail.com> >> wrote: >> > Hi all. Time to start a thread of my own. :) >> > >> > Many of Wicket's powerful repeaters depend on IDataProvider. This >> > interface has a size() method which returns a non-null integer. This >> > makes it easy to determine the total number of pages in a pageable >> > view, but IMO the required computation and application complexity are >> not always called for. >> > In many cases, a pageable but open-ended data view is adequate. Have >> > you experienced this impedance mismatch yourselves? What was your >> solution? >> > >> > To elaborate on my experience: >> > >> > For SQL-based views, the application complexity comes from the need >> to >> > construct a count(*) query with exactly the same criteria as the >> > subsequent result query. In my experience, this pollutes DAO >> > interfaces and IDataProvider implementation non-trivially. We >> > initially had separate methods for counting and querying (same args), >> > but eventually moved to a single method that returns a >> > <List,Integer>-tuple with both the results and total size which our >> > IDataProvider caches. This lets us do some Hibernate trickery to >> > introduce a MySQL SQL_CALC_FOUND_ROWS query hint, avoiding separate >> > count/results queries in most cases. It's still not simple, and for >> large counts is still expensive. >> > >> > The situation is worse for non-SQL data stores which don't have a >> > fully-functional count(*) capability. We use Cassandra whose native >> > "where clause" support is limited, requiring significant client-side >> filtering. >> > Paging through an entire column (or CF) in this way is prohibitively >> > expensive, especially considering our users rarely even go to page 2. >> > To solve this, we've created a parallel set of view/paging classes >> > that define windows using previously discovered result keys instead >> of >> > start indices (tokens and column names in Cassandra). But having a >> > full suite of IUnsizedDataProvider-based classes smells. I love that >> > Wicket devs have solved some tough/tedious problems with DataViewBase >> > and friends, and I want to make use of them! >> > >> > Comments or suggestions? >> > >> > Cheers, >> > Dan >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: users-unsubscr...@wicket.apache.org >> For additional commands, e-mail: users-h...@wicket.apache.org > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@wicket.apache.org > For additional commands, e-mail: users-h...@wicket.apache.org > --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@wicket.apache.org For additional commands, e-mail: users-h...@wicket.apache.org
