See discussions in https://lab.nexedi.com/nexedi/erp5/merge_requests/257 from background.
Here we try to reduce the differences in indexation methods that use DELETE and then INSERT (the one who does not always index the same number of rows).
In z_catalog_predicate_list the DELETE was missing, so in the case of predicate which stopped being a predicate, that predicate was never removed from the table.