-- The gist_page_opaque_info() function prints the page's LSN. Normally,
-- that's constant 1 (GistBuildLSN) on every page of a freshly built GiST
-- index. But with wal_level=minimal, the whole relation is dumped to WAL at
-- the end of the transaction if it's smaller than wal_skip_threshold, which
-- updates the LSNs. Wrap the tests on gist_page_opaque_info() in the
-- same transaction with the CREATE INDEX so that we see the LSNs before
-- they are possibly overwritten at end of transaction.
BEGIN;
-- Create a test table and GiST index.
CREATE TABLE test_gist AS SELECT point(i,i) p, i::text t FROM
    generate_series(1,1000) i;
CREATE INDEX test_gist_idx ON test_gist USING gist (p);
-- Page 0 is the root, the rest are leaf pages
SELECT * FROM gist_page_opaque_info(get_raw_page('test_gist_idx', 0));
 lsn | nsn | rightlink  | flags 
-----+-----+------------+-------
 0/1 | 0/0 | 4294967295 | {}
(1 row)

SELECT * FROM gist_page_opaque_info(get_raw_page('test_gist_idx', 1));
 lsn | nsn | rightlink  | flags  
-----+-----+------------+--------
 0/1 | 0/0 | 4294967295 | {leaf}
(1 row)

SELECT * FROM gist_page_opaque_info(get_raw_page('test_gist_idx', 2));
 lsn | nsn | rightlink | flags  
-----+-----+-----------+--------
 0/1 | 0/0 |         1 | {leaf}
(1 row)

COMMIT;
SELECT * FROM gist_page_items(get_raw_page('test_gist_idx', 0), 'test_gist_idx');
 itemoffset |   ctid    | itemlen | dead |       keys        
------------+-----------+---------+------+-------------------
          1 | (1,65535) |      40 | f    | (p)=((166,166))
          2 | (2,65535) |      40 | f    | (p)=((332,332))
          3 | (3,65535) |      40 | f    | (p)=((498,498))
          4 | (4,65535) |      40 | f    | (p)=((664,664))
          5 | (5,65535) |      40 | f    | (p)=((830,830))
          6 | (6,65535) |      40 | f    | (p)=((996,996))
          7 | (7,65535) |      40 | f    | (p)=((1000,1000))
(7 rows)

SELECT * FROM gist_page_items(get_raw_page('test_gist_idx', 1), 'test_gist_idx') LIMIT 5;
 itemoffset | ctid  | itemlen | dead |    keys     
------------+-------+---------+------+-------------
          1 | (0,1) |      40 | f    | (p)=((1,1))
          2 | (0,2) |      40 | f    | (p)=((2,2))
          3 | (0,3) |      40 | f    | (p)=((3,3))
          4 | (0,4) |      40 | f    | (p)=((4,4))
          5 | (0,5) |      40 | f    | (p)=((5,5))
(5 rows)

-- gist_page_items_bytea prints the raw key data as a bytea. The output of that is
-- platform-dependent (endianess), so omit the actual key data from the output.
SELECT itemoffset, ctid, itemlen FROM gist_page_items_bytea(get_raw_page('test_gist_idx', 0));
 itemoffset |   ctid    | itemlen 
------------+-----------+---------
          1 | (1,65535) |      40
          2 | (2,65535) |      40
          3 | (3,65535) |      40
          4 | (4,65535) |      40
          5 | (5,65535) |      40
          6 | (6,65535) |      40
          7 | (7,65535) |      40
(7 rows)

DROP TABLE test_gist;