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Diffstat (limited to 'doc/src/sgml/btree.sgml')
| -rw-r--r-- | doc/src/sgml/btree.sgml | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/doc/src/sgml/btree.sgml b/doc/src/sgml/btree.sgml index 10abf90189..ca81fbbc84 100644 --- a/doc/src/sgml/btree.sgml +++ b/doc/src/sgml/btree.sgml @@ -433,6 +433,23 @@ returns bool </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> |