\set ECHO none
\pset format unaligned

-- choose() in HAVING over non-numeric value types (here boolean and date) is
-- evaluated in the value-as-text domain via choose's PICKFIRST telescoping:
-- choose() takes the first present row's value. Atoms independent at p = 0.5,
-- rows kept in insertion order. A = (true/2020-01-01, false/2021-02-02),
-- B = (true/2020-01-01).

CREATE TABLE hc(g text, flag boolean, d date);
INSERT INTO hc VALUES
  ('A', true,  DATE '2020-01-01'),
  ('A', false, DATE '2021-02-02'),
  ('B', true,  DATE '2020-01-01');
SELECT add_provenance('hc');
DO $$ BEGIN PERFORM set_prob(provenance(), 0.5) FROM hc; END $$;

-- choose(flag) = true: first present row is the true one, so P(row1 present).
-- A 0.5  B 0.5
CREATE TABLE r1 AS SELECT g, round(probability_evaluate(provenance())::numeric,4) AS p
  FROM hc GROUP BY g HAVING choose(flag) = true;
SELECT remove_provenance('r1'); SELECT 'choose bool' AS q, g, p FROM r1 ORDER BY g;

-- choose(d) = '2020-01-01' over a date column (first present row's date).
-- A 0.5  B 0.5
CREATE TABLE r2 AS SELECT g, round(probability_evaluate(provenance())::numeric,4) AS p
  FROM hc GROUP BY g HAVING choose(d) = DATE '2020-01-01';
SELECT remove_provenance('r2'); SELECT 'choose date' AS q, g, p FROM r2 ORDER BY g;

DROP TABLE r1; DROP TABLE r2; DROP TABLE hc;