Re: Soon-to-be-broken regression test case

On 2018-Oct-11, Tom Lane wrote:

> Hm, I'm not seeing any regression test result changes there. However,
> if you're just executing queries and not EXPLAIN'ing them, it's possible
> something unwanted is happening under the hood.

Hmm, no, the explains are there. Here's one example -- maybe your new
planner smarts do not change these plans for some reason (I note that
you mentioned EXISTS in your OP, which this one does not use; I further
note that we don't use EXISTS anywhere in partition_prune.sql, which
probably amounts to uncovered cases):

prepare ab_q2 (int, int) as
select a from ab where a between $1 and $2 and b < (select 3);

explain (analyze, costs off, summary off, timing off) execute ab_q2 (2, 2);
QUERY PLAN
--------------------------------------------------------
Append (actual rows=0 loops=1)
InitPlan 1 (returns $0)
-> Result (actual rows=1 loops=1)
Subplans Removed: 6
-> Seq Scan on ab_a2_b1 (actual rows=0 loops=1)
Filter: ((a >= $1) AND (a <= $2) AND (b < $0))
-> Seq Scan on ab_a2_b2 (actual rows=0 loops=1)
Filter: ((a >= $1) AND (a <= $2) AND (b < $0))
-> Seq Scan on ab_a2_b3 (never executed)
Filter: ((a >= $1) AND (a <= $2) AND (b < $0))
(10 rows)

--
Álvaro Herrera https://www.2ndQuadrant.com/
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