When i have many many objects of the same type to build, i do something
like this...
function getEvents($sql = '') {
$events = $this->dbh->query("
SELECT cols, cols, FROM table,table
WHERE blah blah balh ($sql ? " AND $sql" : ''),'rows_array');
$rv = array();
foreach($events as $event) {
$rv[] = new CalendarEvent($event);
}
return $rv;
}
my event class takes an array of data and uses phps list function to
load its members. In this case, i save 100s and 100s of queries ,
using just 1. Its a massive improvment if it fits your scheme. To get
one event, i create a method called getEvent($id) that is a wrapper to
getEvents, and only uses the first record.. of coarse, there is only
one record.. but ya.. cheers
Jason
Marcus Bointon <[EMAIL PROTECTED]> wrote:
>
> on 19/8/04 9:49, Krzysztof Gorzelak at [EMAIL PROTECTED] wrote:
>
> > Hi
> > I'm trying my new php5 script, but it takes about 1.2s to generate my page.
> > That is, how my oop model looks like :
> >
> > [category]
> > | | |
> > [photo] [desc] [products]
> >
> >
> > [products]
> > |
> > [product]
> > | | |
> > [photo] [desc] [keys]
> >
> >
> > [keys]
> > |
> > [key]
> > |
> > [values]
> > |
> > [value]
> >
> > Each object gets data from mysql by itself. The generation time of 1
> > category [30 products, 10 keys, 5 values ~= 300 mysql queries] takes as I
> > said more than a 1s (on quite fast machine). How can this model be improved?
> > Do I create too many objects ? What are the oop solutions for such problem ?
>
> This is something that I've wrestled with too. If you make each item you
> deal with a clean, self-sufficient object, with self-storage, data hiding
> etc, it is inevitable that you run into this problem. It is a symptom of a
> fundamental clash between Relational DB and OO points of view. The only
> trick I have found to work around it that is OO-clean is to use factory
> methods or objects that create multiple objects from a single DB query, so
> as well as having a 'get' method that populates an object from a DB, make
> another means of creating an object from local data that has been obtained
> from a larger query that returned sufficient values to populate multiple
> items.
>
> > I also use an extra table to create many-to-many relation betwean a product
> > and a key. Is this the only way in mysql ?
> >
> > [product]
> > |
> > [product_id, key_id]
> > |
> > [key]
>
> Yes, that's the correct way to represent a M:M relation in a relational DB.
> The join table is an artefact of a relational model, rather than an OO one,
> so the answer is to hide the existence of this table within the objects at
> either end - so have product and key objects, but not product_key objects.
> Each object should have a method that retrieves instances of all the related
> objects of the other kind. This is really a different manifestation of the
> first problem.
>
> Ultimately the trick is to create separate factory objects or higher-level
> methods inside the existing objects that can create multiple instances from
> a single database query. Having said that, it's difficult to spot the best
> places to do this. For example, you might normally create multiple product
> objects from an array of database IDs like so:
>
> foreach($productids as $id)
> $products[] = new product($id);
>
> You can see that this would cause a query for each instantiation.
>
> With a product factory class, you might do this instead:
>
> $products = product_factory::get($productids);
>
> Which achieves the same result, but using only a single DB query (hidden
> inside the factory class, which does NOT call the product class in the same
> way!). The next problem is keeping your product_factory and product classes
> in sync - I'm sure there must be a nice pattern to deal with that somewhere.
>
> Marcus
> --
> Marcus Bointon
> Synchromedia Limited: Putting you in the picture
> [EMAIL PROTECTED] | http://www.synchromedia.co.uk
>
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