-- The participants of a parallel CREATE INDEX are a weighted choice (src/col/build_par.c): the build time another participant saves, against the floor of every statement, the bytes and,
-- where the index has a point directory, the lookups that probe one more segment. The function is the choice itself; the default server settings allow 2 workers (3 participants).
CREATE EXTENSION pg_sift;
SET client_min_messages = warning;
CREATE EXTENSION pg_sift_test;

-- rows and columns of the index, whether it has a point directory, the most participants the server allows
SELECT rows, cols, dir, maxp, sift._test_par_participants(rows, cols, dir, maxp) AS participants
FROM (VALUES (100000, 3, true, 3), (300000, 3, true, 3), (450000, 3, true, 3), (450000, 3, false, 3), (600000, 3, true, 3), (1000000, 3, true, 3),
	(300000, 13, true, 3), (300000, 13, false, 3), (1000000, 13, true, 3), (10000000, 13, true, 3), (10000000, 13, true, 16), (10000000, 13, true, 1)) AS t(rows, cols, dir, maxp);

-- a table that the choice builds alone has one segment, and its 500-key lookup probes one
CREATE TABLE pc AS SELECT g AS id, g % 1000 AS v, g % 97 AS w FROM generate_series(1, 300000) g ORDER BY md5((g * 31 + 7)::text);
SET max_parallel_maintenance_workers = 2;
CREATE INDEX pc_i ON pc USING sift_col (id, v, w) WITH (point_tid_columns = 'id');
SELECT current_setting('sift.test_col_workers') AS workers, count(*) AS segments FROM sift.col_segments('pc_i');

DROP TABLE pc;
DROP EXTENSION pg_sift_test;
DROP EXTENSION pg_sift;