-- Planning time grows as N^3 with the number of subqueries that share a base name
-- (PostgreSQL 19 / master, since commit 8c49a484e8e).  Self-contained; run with
-- psql -X -f repro.sql.  Nothing is executed: EXPLAIN without ANALYZE only plans.

-- 1. The names.  Each uncorrelated scalar sublink becomes an InitPlan named by
--    choose_plan_name(glob, "expr", true): expr_1, expr_2, expr_3.
EXPLAIN (COSTS OFF)
SELECT ARRAY[(SELECT 1 WHERE random() >= 0),
             (SELECT 2 WHERE random() >= 0),
             (SELECT 3 WHERE random() >= 0)];

-- Planning time of a statement, from EXPLAIN (SUMMARY), without printing the plan.
CREATE FUNCTION pg_temp.planning_ms(stmt text) RETURNS numeric
LANGUAGE plpgsql AS $$
DECLARE plan json;
BEGIN
  EXECUTE 'EXPLAIN (SUMMARY, FORMAT JSON) ' || stmt INTO plan;
  RETURN round((plan -> 0 ->> 'Planning Time')::numeric, 1);
END $$;

-- 2. The cost: N sublinks (names expr_1 .. expr_N) and an N-arm UNION (every arm
--    planned as its own subquery, names setop_1 .. setop_N).  Doubling N multiplies
--    planning time by about 8.
SELECT n,
       pg_temp.planning_ms((SELECT 'SELECT ARRAY[' || string_agg(format('(SELECT %s WHERE random() >= 0)', i), ', ') || ']'
                            FROM generate_series(1, n) AS i)) AS sublinks_ms,
       pg_temp.planning_ms((SELECT string_agg(format('SELECT %s', i), ' UNION ')
                            FROM generate_series(1, n) AS i)) AS union_ms
FROM (VALUES (250), (500), (1000), (2000)) AS v(n);