-- A key-cut index built at a small maintenance_work_mem is several segments, the last one shorter than the others (a writer is cut at its memory, not at equal
-- shares). They hold disjoint key ranges: each is a partition of the key, nothing is due, and a pass of the rewrite finds nothing to do instead of being asked
-- again and again (the rows are string-heavy: the memory of a writer is mostly dictionary).
CREATE EXTENSION pg_sift;
SET client_min_messages = warning;
SET max_parallel_maintenance_workers = 0;
CREATE TABLE ms (id int, a text, b text, c text) WITH (autovacuum_enabled = false);
INSERT INTO ms SELECT g, md5(g::text) || md5((g * 3)::text), md5((g * 5)::text) || md5((g * 7)::text), md5((g * 11)::text) FROM generate_series(1, 400000) g;
VACUUM (FREEZE, ANALYZE) ms;
SET maintenance_work_mem = '4MB';
CREATE INDEX ms_i ON ms USING sift_col (id, a, b, c) WITH (key_cut = 'id');
SELECT count(*) > 1 AS several_segments FROM sift.col_segments('ms_i') WHERE kind = 'immutable';
 several_segments 
------------------
 t
(1 row)

SELECT sift.col_maintenance_due('ms_i', false) IS NULL AS nothing_due;
 nothing_due 
-------------
 t
(1 row)

SELECT sift.col_verify('ms_i', true);
 col_verify 
------------
 
(1 row)

DROP TABLE ms;
DROP EXTENSION pg_sift;