pageinspect: Add tests

contrib/pageinspect/expected/gin.out

@@ -0,0 +1,30 @@
+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);
+\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
+DROP TABLE test1;