ps_product_attribute and ps_product_attribute_combination tables grown huge

[Marek]

I was asked to upgrade the PS from 1.6.0.14 to the latest 1.6. I managed to setup the testing environment but I noticed an awkward thing. Some of the tables are surprisingly big (data from phpMyAdmin):

ps_product_attribute_combination - 1.2 GiB - 21.900.197
ps_product_attribute - 758 MiB - 4.311.096
ps_stock_available - 627.9 MiB - 4.607.251
ps_product_attribute_shop - 389 MiB - 4.379.841

and those are only the biggest in terms of MiB size. I'm not a very experienced PS user but is seems pretty strange for the installation that has 8488 products with 64 attributes defined. Even the cartesian product would not give such numbers...

Obviously with such amount of data the upgrade operation will be at least hard (1-Click already failed because of timeouts) so I need to figure out how to slim product-related tables down somehow.

Any idea why they grown so huge and how to deal with it?