-- sift.col_index_info.units of a key-cut index: the units of a key-cut segment are numbered from 0 in each segment, so the segments of a parallel build
-- share those numbers and are not superblocks that one segment covers once. units is the units stored, as the units of col_segments and the pre-aggregates count them.
CREATE EXTENSION pg_sift;
SET client_min_messages = warning;
SET min_parallel_table_scan_size = 0;
SET max_parallel_maintenance_workers = 2;
SET parallel_leader_participation = off;

CREATE TABLE ku (id int, g int, v int, pad text) WITH (autovacuum_enabled = off);
INSERT INTO ku SELECT i, i % 40, i % 1000, repeat('x', 200) FROM generate_series(1, 60000) i;
VACUUM (FREEZE, ANALYZE) ku;

CREATE FUNCTION ku_units(idx regclass) RETURNS TABLE (segments_ok bool, units_stored bool, preagg_within bool, advice_same bool) LANGUAGE sql AS $$
	SELECT i.segments > 1, i.units = (SELECT sum(s.units) FROM sift.col_segments(idx) s WHERE s.kind = 'immutable'), i.preagg_units <= i.units,
	       (SELECT a.units FROM sift.cluster_advice(idx::text::regclass, 1) a) IS NOT DISTINCT FROM i.units
	FROM sift.col_index_info(idx) i $$;

-- key cut, several segments
-- the segments of the workers, which the build merges when nothing says otherwise (col_build_standby_space): the layout a build of 3.6.0 left, which an older index still has
SET sift.col_auto_merge_fragmentation = 1000;
SET sift.test_col_gap_blocks = 0;
CREATE INDEX ku_key ON ku USING sift_col (id, g, v) WITH (key_cut = 'g');
RESET sift.col_auto_merge_fragmentation;
RESET sift.test_col_gap_blocks;
SELECT * FROM ku_units('ku_key');

-- not cut by a key: the superblocks are shared and counted once
CREATE INDEX ku_plain ON ku USING sift_col (id, g, v) WITH (key_cut = 'off');
SELECT segments > 1 AS segments_ok, units = (SELECT count(DISTINCT sb) FROM sift.col_unit_agg('ku_plain', 'g') WHERE segment IS NOT NULL) AS superblocks_once, preagg_units <= units AS preagg_within
FROM sift.col_index_info('ku_plain');

DROP TABLE ku;
DROP FUNCTION ku_units(regclass);
DROP EXTENSION pg_sift;