There is a fundamental performance problem with ZenMagick and very large categories. Since ZenMagick does all it’s sorting and filtering in PHP, rather than SQL, it’s easy to see why.

Main reason for this design decision was that it seems to be easier to add new filter and sort options this way. Another side effect is that price sorting is done on the actual calculated prices rather than the internal cost price.

To get around some of these limitations I have started on a new plugin that will use zen-cart’s default_filter code in combinations with it’s split_page_results class. This should make category pages perform more or less the same in both systems.

Filters are not implemented right now but should hopefully ready for the next release.