On 2018-Oct-11, Tom Lane wrote:
> I have been fooling around with a patch to allow pull-up of sub-selects
> that lack any FROM, along the lines discussed in
> https://www.postgresql.org/message-id/15944.1521127664@sss.pgh.pa.us
> I find that it is smart enough to reduce that EXISTS to a plain
> expression, yielding
>
> QUERY PLAN
> ----------------------------------------------------
> Subquery Scan on tenk1_vw_sec
> -> Index Only Scan using tenk1_unique1 on tenk1
> Index Cond: (unique1 = 0)
> (3 rows)
Hmm, I have the feeling that this would nullify some tests in
partition_prune also, which IIRC pretend to invoke runtime pruning with
things like "WHERE partcol = (select 1)".
--
Álvaro Herrera https://www.2ndQuadrant.com/
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