pageinspect: Fix gist_page_items() with included columns

Non-leaf pages of GiST indexes contain key attributes, leaf pages
contain both key and non-key attributes, and gist_page_items() ignored
the handling of non-key attributes.  This caused a few problems when
using gist_page_items() on a GiST index with INCLUDE:
- On a non-leaf page, the function would crash.
- On a leaf page, the function would work, but miss to display all the
values for included attributes.

This commit fixes gist_page_items() to handle such cases in a more
appropriate way, and now displays the values of key and non-key
attributes for each item separately in a style consistent with what
ruleutils.c would generate for the attribute list, depending on the page
type dealt with.  In a way similar to how a record is displayed, values
would be double-quoted for key or non-key attributes if required.

ruleutils.c did not provide a routine able to control if non-key
attributes should be displayed, so an extended() routine for index
definitions is added to work around the leaf and non-leaf page
differences.

While on it, this commit fixes a third problem related to the amount of
data reported for key attributes.  The code originally relied on
BuildIndexValueDescription() (used for error reports on constraints)
that would not print all the data stored in the index but the index
opclass's input type, so this limited the amount of information
available.  This switch makes gist_page_items() much cheaper as there is
no need to run ACL checks for each item printed, which is not an issue
anyway as superuser rights are required to execute the functions of
pageinspect.  Opclasses whose data cannot be displayed can rely on
gist_page_items_bytea().

The documentation of this function was slightly incorrect for the
output results generated on HEAD and v15, so adjust it on these
branches.

Author: Alexander Lakhin, Michael Paquier
Discussion: https://postgr.es/m/17884-cb8c326522977acb@postgresql.org
Backpatch-through: 14

1 files changed, 14 insertions, 0 deletions

diff --git a/contrib/pageinspect/sql/gist.sql b/contrib/pageinspect/sql/gist.sql
index 4787b784a46..d263542ba15 100644
--- a/contrib/pageinspect/sql/gist.sql
+++ b/contrib/pageinspect/sql/gist.sql
@@ -52,4 +52,18 @@ SELECT gist_page_items_bytea(decode(repeat('00', :block_size), 'hex'));
 SELECT gist_page_items(decode(repeat('00', :block_size), 'hex'), 'test_gist_idx'::regclass);
 SELECT gist_page_opaque_info(decode(repeat('00', :block_size), 'hex'));
 
+-- Test gist_page_items with included columns.
+-- Non-leaf pages contain only the key attributes, and leaf pages contain
+-- the included attributes.
+ALTER TABLE test_gist ADD COLUMN i int DEFAULT NULL;
+CREATE INDEX test_gist_idx_inc ON test_gist
+  USING gist (p) INCLUDE (t, i);
+-- Mask the value of the key attribute to avoid alignment issues.
+SELECT regexp_replace(keys, '\(p\)=\("(.*?)"\)', '(p)=("<val>")') AS keys_nonleaf_1
+  FROM gist_page_items(get_raw_page('test_gist_idx_inc', 0), 'test_gist_idx_inc')
+  WHERE itemoffset = 1;
+SELECT keys AS keys_leaf_1
+  FROM gist_page_items(get_raw_page('test_gist_idx_inc', 1), 'test_gist_idx_inc')
+  WHERE itemoffset = 1;
+
 DROP TABLE test_gist;