see below...
-----Original Message-----
From: Igor Vaynberg [mailto:[EMAIL PROTECTED]
Sent: Monday, March 24, 2008 5:13 PM
To: [email protected]
Subject: Re: DataView size() iterator() call order issue
how are we going to cover these usecases:
* pagination toolbar needs to call dataprovier.size() to figure out
how many total records there are. at this point the toolbar doesnt
know what window of data to retrieve, it just wants to know the size.
[Will]: Currently, the size() method is called twice when paginating using
PagingNavigator (not to mention the call for isvisible you describe below).
This causes issues with duplicate query calls if the count is queried in the
size() method. Could there be transient properties in the data provider that
cache the count/list of items that would be cleared when rendered? If that were
the case there could be an abstract method defined in the data provider
interface to query/set the results.
* often users do:
new dataview() { isvisible() { return dataprovider.size()>0; }
once again, datawindow size is not known.
[Will]: This would be accommodated by the above solution.
-igor
On Mon, Mar 24, 2008 at 6:52 AM, Hoover, William <[EMAIL PROTECTED]> wrote:
> We are using a modified version of the Generic DAO for Hibernate
> (http://www.hibernate.org/328.html) where we make reuse of common DAO methods
> such as keyword searches that retrieve corresponding entities as well a total
> size (both use the same search criteria when determining results so it makes
> sense to combine the operations). As you stated, we are making two calls the
> database, but only one call to the DAO (although, as stated in previous
> responses there are alternative ways to perform one query to achieve this).
>
> Our business tier handles the transactions for us (not our DAOs ;o) using an
> event model (similar to typical BPM systems). Broadcast agents are used to
> notify our business listeners which in turn process our DAO calls. This gives
> us an the flexibility to have independent transactions for different business
> rule operations and makes the most out of code reuse.
>
> Avoiding the heavier call makes perfect sense, but couldn't this
> responsibility be passed to the data provider implementation? It may make
> more sense if the operation were combined so that the implementation could
> determine how/when to make the call to the persistence tier for the two
> operations. I guess I'm not seeing why we need the count before the iterator.
> The data provider impl can determine whether or not it will make the
> expensive call for the results.
>
>
> -----Original Message-----
> From: Igor Vaynberg [mailto:[EMAIL PROTECTED]
>
> Sent: Friday, March 21, 2008 2:44 PM
> To: [email protected]
> Subject: Re: DataView size() iterator() call order issue
>
>
>
>
> knowing the size and the window together seems like a ui requirement,
> it is a bit strange to me that you have it inside a dao which should
> cater to business logic. eg, as far as i know there is no single db
> operation that will produce both, so you are still doing two calls
> inside the dao.
>
> also transaction management should be handled outside the dao, daos
> are too fine an object to implement transaction management for.
>
> anywho, just nitpicking :)
>
> size() is called first for a lot of reasons, namely even knowing if
> there are any rows to retrieve before a much heavier iterator() is
> called. some clients want to hide a repeater if there are no items
> visible, and so size() might get called from inside isvisible() as
> well.
>
> idataprovider is quiet old and we havent had many complaints about its
> design so far. if all you are using is the dataview it should be
> pretty simple for you to roll your own dataview, if you look at
> dataview all it does is implement idataprovider handling to feed the
> pageable view. however, if you do you will also lose datatable as well
> :|
>
> if you got suggestions on how to improve it im all ears.
>
> -igor
>
>
> On Fri, Mar 21, 2008 at 11:24 AM, Hoover, William <[EMAIL PROTECTED]> wrote:
> > When using DataView/IDataProvider size() is called before iterator(int
> first, int count) causing calls to DAOs to be duplicated. Our current
> framework that is internally using Hibernate allows one call to be made to a
> DAO that returns both the total result size and the actual records (based off
> first/count). The problem is that the first and count are unknown until the
> iterator method is called- forcing multiple calls to the DAO to retrieve the
> data (also forcing multiple transactions). What are the reasons behind
> calling size before iterator?
> >
> >
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