Użytkownik "Jason Davidson" <[EMAIL PROTECTED]> napisał w wiadomości news:[EMAIL PROTECTED] > 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 > > --
Thanks a lot, after your replies I made a little google search on 'factory class' and found a great article: http://www.phppatterns.com/index.php/article/articleview/49/1/1/. My objects are still too slow (0,3s) but now I'm going to try Advanced PHP Debugger. Krzysztof Gorzelak -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
