Can anyone tell me if the getItems() function in the model automatically adds the globally set LIMIT before it actions the query (from getListQuery()). Joomla is really struggling, seemingly trying to cache the entire results (over 1 million records here!).
After looking in /libraries/legacy/model/list.php AND /libraries/legacy/model/legacy.php it appears that getItems() does add LIMIT to setQuery using $this->getState('list.limit') before it sends the results to the cache but if this is the case - why is Joomla struggling so much.
So what's going on? How come phpMyAdmin can return the limited results within a second and Joomla just times out?
Many thanks!
It does add the pagination automatically.
Its struggling is most likely due to a large dataset (i.e. 1000+ items returned in the collection) and many lookup fields: the content modules for example join as many as 10 tables, to get author names etc.
This can be a real killer, I had queries running for over one second with a dedicated server and only 3000 content items. One tag cloud component we found could take as long as 45 seconds to return a keywords list. If this is the situation (a lot of records and many joins), your only way out is to further limit the filters in the options to see if you can get some faster results (for example, limiting to articles in the last 3 months can reduce the time needed dramatically).
But if this is not sufficient or not viable, you're left with writing a new optimized query in a new model, which ultimately will bring the best performance optimization of any other optimization. In writing the query, consider leveraging the database specific optimizations, i.e. adding indexes, full-text indexes and only use joins if you really need them.
Also consider that joins must never grow with the number of fields, translations or else.
A constant query is easy for the db engine to optimize and cache, whilst a dynamic query will never be as efficient.