CREATE TABLE test1 (x int, y int[]);
INSERT INTO test1 VALUES (1, ARRAY[11, 111]);
CREATE INDEX test1_y_idx ON test1 USING gin (y) WITH (fastupdate = off);
\x
SELECT * FROM gin_metapage_info(get_raw_page('test1_y_idx', 0));
-[ RECORD 1 ]----+-----------
pending_head     | 4294967295
pending_tail     | 4294967295
tail_free_size   | 0
n_pending_pages  | 0
n_pending_tuples | 0
n_total_pages    | 2
n_entry_pages    | 1
n_data_pages     | 0
n_entries        | 2
version          | 2

SELECT * FROM gin_metapage_info(get_raw_page('test1_y_idx', 1));
ERROR:  input page is not a GIN metapage
DETAIL:  Flags 0002, expected 0008
SELECT * FROM gin_page_opaque_info(get_raw_page('test1_y_idx', 1));
-[ RECORD 1 ]---------
rightlink | 4294967295
maxoff    | 0
flags     | {leaf}

SELECT * FROM gin_leafpage_items(get_raw_page('test1_y_idx', 1));
ERROR:  input page is not a compressed GIN data leaf page
DETAIL:  Flags 0002, expected 0083
INSERT INTO test1 SELECT x, ARRAY[1,10] FROM generate_series(2,10000) x;
SELECT COUNT(*) > 0
FROM gin_leafpage_items(get_raw_page('test1_y_idx',
                        (pg_relation_size('test1_y_idx') /
                         current_setting('block_size')::bigint)::int - 1));
-[ RECORD 1 ]
?column? | t