-- A VACUUM that vacuums the b-trees of a table with parallel workers runs the sift_col index in the leader, in parallel mode, where no transaction id may be assigned and no
-- catalog row written: a merge there leaves the key_columns = 'auto' decision to the next merge instead of failing with "cannot assign transaction IDs during
-- a parallel operation".
SET client_min_messages = warning;
CREATE EXTENSION pg_sift_test CASCADE;
SET sift.col_auto_merge = off;
SET max_parallel_workers_per_gather = 0;
CREATE FUNCTION pv_opt(idx regclass) RETURNS text LANGUAGE sql AS $$ SELECT coalesce(array_to_string(reloptions, ','), '') FROM pg_class WHERE oid = idx $$;
-- clustered by set_id: about 6 owners in a unit, which the cube holds; two b-trees and the primary key for the workers of the VACUUM
CREATE TABLE pv (id int PRIMARY KEY, set_id int, v int, pad text) WITH (autovacuum_enabled = off);
INSERT INTO pv SELECT i, i / 500, i % 100, repeat('p', 200) FROM generate_series(0, 29999) i;
CREATE INDEX pv_v ON pv (v);
CREATE INDEX pv_owner ON pv (set_id);
VACUUM (FREEZE, DISABLE_PAGE_SKIPPING) pv;
CREATE INDEX pv_idx ON pv USING sift_col (id, set_id, v);
SELECT pv_opt('pv_idx') AS built;
                            built                             
--------------------------------------------------------------
 track_changes=id,point_tid_columns=auto: id,key_columns=auto
(1 row)

-- two rounds of non-HOT updates that scatter the owners, each promoted into its own segment
UPDATE pv SET set_id = (id::bigint * 7919 % 600)::int;
VACUUM pv;
SELECT sift.col_promote('pv_idx') > 0 AS promoted;
 promoted 
----------
 f
(1 row)

UPDATE pv SET set_id = (id::bigint * 104729 % 600)::int;
VACUUM pv;
SELECT sift.col_promote('pv_idx') > 0 AS promoted;
 promoted 
----------
 f
(1 row)

-- rows to remove, so that the index is vacuumed; every index is big enough for a worker
DELETE FROM pv WHERE id % 20 = 3;
SET min_parallel_index_scan_size = 0;
SET max_parallel_maintenance_workers = 2;
VACUUM (PARALLEL 2) pv;
SELECT pv_opt('pv_idx') AS after_parallel_vacuum;
                    after_parallel_vacuum                     
--------------------------------------------------------------
 track_changes=id,point_tid_columns=auto: id,key_columns=auto
(1 row)

-- outside parallel mode the merge decides
RESET max_parallel_maintenance_workers;
SELECT sift.col_merge('pv_idx', true) >= 0 AS merged;
 merged 
--------
 t
(1 row)

SELECT pv_opt('pv_idx') AS after_merge;
                             after_merge                              
----------------------------------------------------------------------
 track_changes=id,key_columns=auto: set_id,point_tid_columns=auto: id
(1 row)

DROP TABLE pv;
DROP FUNCTION pv_opt(regclass);
DROP EXTENSION pg_sift_test, pg_sift CASCADE;