> Risky to try in prod server. Requires creating randomly distributed
> product_id testcase to measure
> difference.
>
> What should I do next?
I guess you have backups - take them, restore the database on a
different machine (preferably with the same / similar hw config) and
tune the queries on it.
After restoring all the tables / indexes will be 'clean' (not bloated),
so you'll see if performing VACUUM FULL / CLUSTER is the right solution
or if you have to change the application internals.
Sure, the times will be slightly different but the performance problems
should remain the same.
regards
Tomas