E.g. Flag activities have an array of objects
We prune the activity when NONE of the objects can be found
Note that the cost of finding and deleting these is ~4x higher than finding and deleting the non-array ones
Only string:
Delete on activities (cost=506573.48..506580.38 rows=0 width=0)
Only Array:
Delete on activities (cost=3570359.68..4276365.34 rows=0 width=0)
(They are still executed separately, so the total cost is the sum of the two)
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