[ http://jira.codehaus.org/browse/DISPL-122?page=all ]
fabrizio giustina closed DISPL-122:
-----------------------------------
Resolution: Duplicate
see DISPL-122 and DISPL-129
> Increase efficiency paging using a subset (patch included)
> ----------------------------------------------------------
>
> Key: DISPL-122
> URL: http://jira.codehaus.org/browse/DISPL-122
> Project: DisplayTag
> Type: Improvement
> Components: Paging/Sorting
> Versions: 1.0 RC2
> Reporter: fabrizio giustina
> Fix For: 1.1
> Attachments: DISPL-122.diff
>
>
> ====
> imported from sf tracker
> id 1013526
> submitted by Will Glass-Husain - wglass
> http://sourceforge.net/support/tracker.php?aid=1013526
> ====
> [This really belongs in issue#872183 but I couldn't figure
> out how to add another file to the issue.]
> The dilemma - how to efficiently display a large list (e.g.
> 20,000 rows) one page at a time. Currently, to take
> advantage of DisplayTag's paging features, you must
> generate the entire list each request.
> This patch allows the application to control the
> selection of the specific sublist, with DisplayTag
> automatically generating the PREV/NEXT links as usual.
> For an MVC environment pulling large lists out of a
> database this can be used to implement significant
> performance improvements.
> There's already a patch solving the same problem in the
> issue tracker (#872183), but I've made an alternate
> implementation (not having seen the first proposal at
> the time). This particular patch may be easier to
> integrate than the previous one (being based on a more
> recent version of DisplayTag). It is fully backwards
> compatible, works with EL tags, and is configurable with
> DisplayTag properties rather than any new attributes.
> Using it is not too complicated, although it requires
> coordination between the Controller code and the JSP
> page. There are two new DisplayTag properties:
> paging.manual (true/false, default: false)
> paging.manual.prefix (default "d")
> In order to produce a table, the controller must
> generate the sublist, calculate the size of the full list,
> and pass both pieces of info to DisplayTag. (both are
> required for paging). The size of the full list is passed
> by setting a pageContext attribute with the name of "d-
> size". (or X-size, if X is the prefix specified with
> the "paging.manual.prefix" property). DisplayTag will
> display the sublist amd will also generate page hyperlinks
> for the full list. Each hyperlink will contain a request
> parameter "d-p", e.g. "d-p=2". (This is similar to the
> standard page parameter which is typically something
> like "d-2911-p=2"). When the hyperlink is clicked, the
> controller should note the new page number and send
> along a new sublist.
> Example pseudo code:
> CONTROLLER:
> int pagesize = 10;
> int fulllistsize = <count the size of the full list>
> List sublist = <generate sublist for the particular page,
> based on a page size of 10>
> pageContext.setAttribute("list",sublist);
> pageContext.setAttribute("d-size",fulllistsize);
> JSP PAGE:
> <display:table name="${list}" pagesize="10">
> <display:setProperty name="paging.manual"
> value="false" />
> .. all the display columns
> </display:table>
> A key issue the patch had to address is how to
> distinguish one TableTag from another if there are
> multiple instances on the same page. This is normally
> done with an automatically generated id. In this case
> however, since the request parameters must be
> recognized by the controller to generate the sublist, the
> id is skipped and the prefix (specified in the properties)
> is used instead. Thus it is up to the page designer to
> use different prefixes for different DisplayTag tables on
> the same page.
> I'd welcome any comments.
> Note: this patch was made against nightly build of 8-16-
> 04, 1.0-rc2 SNAPSHOT.
> ======
> Date: 2004-09-13 21:48
> Sender: ralfhauser
> Logged In: YES
> user_id=266141
> see also another solution in
> http://sourceforge.net/tracker/index.php?func=detail&aid=1026408&;
> group_id=73068&atid=536613
> ====
> Date: 2004-09-07 03:50
> Sender: ianbdev
> Logged In: YES
> user_id=461701
> Hello,
> I posted the 872183 request.
> Since then we've come up with an alternate approach.
> See [ 1023387 ] Pagination - use subList instead of iterating
> all records.
> If this change is implemented then you can implement a List
> object that overrides the subList method of the List interface.
> This would allow you to limit database/datasource accesses
> to obtain just the few page records required for the page
> being displayed.
> No other changes to display tag are required.
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