-- The completeness record of a tombstone log is in the header page of the log, and a header written before the record has fewer used bytes: whatever the page holds past them is
-- not a record. A page can hold one nonetheless (a page that held a complete log before and is given to another header), and a log taken for complete on its word would make a read
-- skip the heap for deletes it never heard. The oracle is the heap: the reads are the same with and without the log's say.
CREATE EXTENSION pg_sift;
CREATE EXTENSION pg_sift_test;
SET client_min_messages = warning;
SET max_parallel_workers_per_gather = 0;
CREATE TABLE events (id int PRIMARY KEY, tenant_id int NOT NULL, counter_a int, label text) WITH (autovacuum_enabled = false, fillfactor = 100);
INSERT INTO events SELECT i, i % 10, i, 'x' FROM generate_series(1, 20000) i;
CREATE INDEX events_c ON events USING sift_col (id, tenant_id, counter_a) WITH (track_changes = 'id');
VACUUM events;
SELECT track_changes, triggers, complete, heap_free FROM sift.col_tracking('events_c');
 track_changes | triggers | complete | heap_free 
---------------+----------+----------+-----------
 t             | t        | t        | t
(1 row)

SELECT * FROM sift._test_tomb_header('events_c');
 covered | flags 
---------+-------
 t       |     3
(1 row)

-- the page of a release before the record, with the bytes of a complete record still on it
SELECT * FROM sift._test_tomb_header('events_c', true, true);
 covered | flags 
---------+-------
 f       |     3
(1 row)

SELECT track_changes, triggers, complete, heap_free FROM sift.col_tracking('events_c');
 track_changes | triggers | complete | heap_free 
---------------+----------+----------+-----------
 t             | f        | f        | f
(1 row)

-- the reads: an update of a column the index does not cover clears the visibility map and writes nothing to the log (the page of the header is not written again); the log is not known
-- to be complete, so the heap checks and the answer is the table's
UPDATE events SET label = 'y' WHERE id % 13 = 0;
SET sift.enable_agg = on;
SELECT sift._test_hf_taken(true) AS reset;
 reset 
-------
     0
(1 row)

SELECT tenant_id, count(*), sum(counter_a) FROM events GROUP BY tenant_id ORDER BY 1;
 tenant_id | count |   sum    
-----------+-------+----------
         0 |  2000 | 20010000
         1 |  2000 | 19992000
         2 |  2000 | 19994000
         3 |  2000 | 19996000
         4 |  2000 | 19998000
         5 |  2000 | 20000000
         6 |  2000 | 20002000
         7 |  2000 | 20004000
         8 |  2000 | 20006000
         9 |  2000 | 20008000
(10 rows)

SELECT sift._test_hf_taken() AS taken_from_the_log;
 taken_from_the_log 
--------------------
                  0
(1 row)

SET sift.enable_agg = off;
SELECT tenant_id, count(*), sum(counter_a) FROM events GROUP BY tenant_id ORDER BY 1;
 tenant_id | count |   sum    
-----------+-------+----------
         0 |  2000 | 20010000
         1 |  2000 | 19992000
         2 |  2000 | 19994000
         3 |  2000 | 19996000
         4 |  2000 | 19998000
         5 |  2000 | 20000000
         6 |  2000 | 20002000
         7 |  2000 | 20004000
         8 |  2000 | 20006000
         9 |  2000 | 20008000
(10 rows)

-- a new baseline writes the record again
RESET sift.enable_agg;
ALTER INDEX events_c SET (track_changes = 'off');
ALTER INDEX events_c SET (track_changes = 'id');
SELECT * FROM sift._test_tomb_header('events_c');
 covered | flags 
---------+-------
 f       |     3
(1 row)

SELECT track_changes, triggers, complete, heap_free FROM sift.col_tracking('events_c');
 track_changes | triggers | complete | heap_free 
---------------+----------+----------+-----------
 t             | f        | f        | f
(1 row)

DROP TABLE events;
DROP EXTENSION pg_sift_test;
DROP EXTENSION pg_sift;