</sect1>
-<sect1 id="btree-included-attributes">
- <title>Included attributes in B-tree indexes</title>
-
- <para>
- As of <productname>PostgreSQL</productname> 11.0 there is an optional
- INCLUDE clause, which allows to add non-key (included) attributes to index.
- Those included attributes allow more queries to benefit from index-only scans.
- We never use included attributes in ScanKeys for search. That allows us to
- include into B-tree any datatypes, even those which don't have suitable
- operator classes. Included columns only stored in regular tuples on leaf
- pages. All pivot tuples on non-leaf pages and highkey tuples are truncated
- to contain only key attributes. That helps to slightly reduce the size of
- index.
- </para>
-
-</sect1>
-
<sect1 id="btree-implementation">
<title>Implementation</title>