CREATE TABLE test1 (a int, b text);
INSERT INTO test1 VALUES (1, 'one');
CREATE INDEX test1_a_idx ON test1 USING brin (a);
SELECT brin_page_type(get_raw_page('test1_a_idx', 0));
 brin_page_type 
----------------
 meta
(1 row)

SELECT brin_page_type(get_raw_page('test1_a_idx', 1));
 brin_page_type 
----------------
 revmap
(1 row)

SELECT brin_page_type(get_raw_page('test1_a_idx', 2));
 brin_page_type 
----------------
 regular
(1 row)

SELECT * FROM brin_metapage_info(get_raw_page('test1_a_idx', 0));
   magic    | version | pagesperrange | lastrevmappage 
------------+---------+---------------+----------------
 0xA8109CFA |       1 |           128 |              1
(1 row)

SELECT * FROM brin_metapage_info(get_raw_page('test1_a_idx', 1));
ERROR:  page is not a BRIN page of type "metapage"
DETAIL:  Expected special type 0000f091, got 0000f092.
SELECT * FROM brin_revmap_data(get_raw_page('test1_a_idx', 0)) LIMIT 5;
ERROR:  page is not a BRIN page of type "revmap"
DETAIL:  Expected special type 0000f092, got 0000f091.
SELECT * FROM brin_revmap_data(get_raw_page('test1_a_idx', 1)) LIMIT 5;
 pages 
-------
 (2,1)
 (0,0)
 (0,0)
 (0,0)
 (0,0)
(5 rows)

SELECT * FROM brin_page_items(get_raw_page('test1_a_idx', 2), 'test1_a_idx')
    ORDER BY blknum, attnum LIMIT 5;
 itemoffset | blknum | attnum | allnulls | hasnulls | placeholder |  value   
------------+--------+--------+----------+----------+-------------+----------
          1 |      0 |      1 | f        | f        | f           | {1 .. 1}
(1 row)

DROP TABLE test1;