Attached documentation patch describes the purpose of
bt_page_items()'s ctid field. This has come up enough times in
disaster recovery or testing scenarios that I feel it's worth drawing
particular attention to.
--
Peter Geoghegan
diff --git a/doc/src/sgml/pageinspect.sgml b/doc/src/sgml/pageinspect.sgml
index 6f51dc6..433bcb2 100644
--- a/doc/src/sgml/pageinspect.sgml
+++ b/doc/src/sgml/pageinspect.sgml
@@ -192,6 +192,13 @@ test=# SELECT * FROM bt_page_items('pg_cast_oid_index', 1);
7 | (0,7) | 12 | f | f | 29 27 00 00
8 | (0,8) | 12 | f | f | 2a 27 00 00
</screen>
+ Note that <structfield>ctid</> addresses a heap tuple if the
+ page under consideration is a B-Tree leaf page. Otherwise, for
+ internal B-Tree pages <structfield>ctid</> addresses a page in
+ the B-Tree itself (excluding the root page if and only if there
+ has not yet been a root page split, as in the example above).
+ These internally referenced pages are child pages, and may
+ themselves be leaf pages or internal pages.
</para>
</listitem>
</varlistentry>
--
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