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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