Hm, shouldn't this query notice that random() is volatile and not make the
subquery an initplan?
postgres=# select i, (select (random()*1000)::integer ) from x limit 5;i | ?column?
---+----------1 | 6772 | 6773 | 6774 | 6775 | 677
(5 rows)
postgres=# explain select i, (select (random()*1000)::integer ) from x limit 5; QUERY PLAN
-----------------------------------------------------------Limit (cost=0.02..0.11 rows=5 width=4) InitPlan ->
Result (cost=0.00..0.02 rows=1 width=0) -> Seq Scan on x (cost=0.00..64.80 rows=3480 width=4)
(4 rows)
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