-- The unit that holds the rows of a heap block (sift_cseg_unit_of_block): a segment cut by superblock answers the unit of the block's superblock, or none; a segment cut by key
-- has no unit by block and says unknown, whatever the block. A caller that took the address of a row for a superblock got the wrong unit in the released 3.6.0 and
-- 3.6.1 (rows missing from bitmap and index scans); every reader of the mapping goes through this answer now.
CREATE EXTENSION pg_sift;
CREATE EXTENSION pg_sift_test;
SET sift.async_maintenance = off;
SET max_parallel_maintenance_workers = 0;
SET client_min_messages = warning;
\set VERBOSITY terse
-- fillfactor 20 and a padded row: a few rows a page, 3000 pages, twelve superblocks of 256 pages
CREATE TABLE ub (id int, ent int, pad text) WITH (fillfactor = 20, autovacuum_enabled = false);
INSERT INTO ub SELECT i, 1 + i % 40, repeat('x', 1500) FROM generate_series(1, 3000) i;
VACUUM (FREEZE, ANALYZE) ub;
SELECT pg_relation_size('ub') / current_setting('block_size')::int AS pages;
 pages 
-------
  3000
(1 row)

CREATE INDEX ub_sb ON ub USING sift_col (id, ent) WITH (key_cut = 'off');
SELECT blk, seg, keyed, unit, outcome FROM unnest(ARRAY[0, 255, 256, 511, 512, 100000]::int8[]) blk, sift._test_col_unit_of_block('ub_sb', blk) ORDER BY blk, seg;
  blk   | seg | keyed | unit | outcome 
--------+-----+-------+------+---------
      0 |   0 | f     |    0 | unit
    255 |   0 | f     |    0 | unit
    256 |   0 | f     |    1 | unit
    511 |   0 | f     |    1 | unit
    512 |   0 | f     |    2 | unit
 100000 |   0 | f     |      | none
(6 rows)

DROP INDEX ub_sb;
CREATE INDEX ub_key ON ub USING sift_col (id, ent) WITH (key_cut = 'ent');
SELECT blk, seg, keyed, unit, outcome FROM unnest(ARRAY[0, 255, 256, 511, 512, 100000]::int8[]) blk, sift._test_col_unit_of_block('ub_key', blk) ORDER BY blk, seg;
  blk   | seg | keyed | unit | outcome 
--------+-----+-------+------+---------
      0 |   0 | t     |      | unknown
    255 |   0 | t     |      | unknown
    256 |   0 | t     |      | unknown
    511 |   0 | t     |      | unknown
    512 |   0 | t     |      | unknown
 100000 |   0 | t     |      | unknown
(6 rows)

DROP TABLE ub;
DROP EXTENSION pg_sift_test;
DROP EXTENSION pg_sift;