Indexes with INCLUDE columns and their support in B-tree

This patch introduces INCLUDE clause to index definition.  This clause
specifies a list of columns which will be included as a non-key part in
the index.  The INCLUDE columns exist solely to allow more queries to
benefit from index-only scans.  Also, such columns don't need to have
appropriate operator classes.  Expressions are not supported as INCLUDE
columns since they cannot be used in index-only scans.

Index access methods supporting INCLUDE are indicated by amcaninclude flag
in IndexAmRoutine.  For now, only B-tree indexes support INCLUDE clause.

In B-tree indexes INCLUDE columns are truncated from pivot index tuples
(tuples located in non-leaf pages and high keys).  Therefore, B-tree indexes
now might have variable number of attributes.  This patch also provides
generic facility to support that: pivot tuples contain number of their
attributes in t_tid.ip_posid.  Free 13th bit of t_info is used for indicating
that.  This facility will simplify further support of index suffix truncation.
The changes of above are backward-compatible, pg_upgrade doesn't need special
handling of B-tree indexes for that.

Bump catalog version

Author: Anastasia Lubennikova with contribition by Alexander Korotkov and me
Reviewed by: Peter Geoghegan, Tomas Vondra, Antonin Houska, Jeff Janes,
			 David Rowley, Alexander Korotkov
Discussion: https://www.postgresql.org/message-id/flat/56168952.4010101@postgrespro.ru

1 files changed, 6 insertions, 3 deletions

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 538e679cdf3..4ad5131aa97 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -118,9 +118,11 @@ typedef struct ExprState
  *		entries for a particular index.  Used for both index_build and
  *		retail creation of index entries.
  *
- *		NumIndexAttrs		number of columns in this index
+ *		NumIndexAttrs		total number of columns in this index
+ *		NumIndexKeyAttrs	number of key columns in index
  *		KeyAttrNumbers		underlying-rel attribute numbers used as keys
- *							(zeroes indicate expressions)
+ *							(zeroes indicate expressions). It also contains
+ * 							info about included columns.
  *		Expressions			expr trees for expression entries, or NIL if none
  *		ExpressionsState	exec state for expressions, or NIL if none
  *		Predicate			partial-index predicate, or NIL if none
@@ -146,7 +148,8 @@ typedef struct ExprState
 typedef struct IndexInfo
 {
 	NodeTag		type;
-	int			ii_NumIndexAttrs;
+	int			ii_NumIndexAttrs;	/* total number of columns in index */
+	int			ii_NumIndexKeyAttrs;	/* number of key columns in index */
 	AttrNumber	ii_KeyAttrNumbers[INDEX_MAX_KEYS];
 	List	   *ii_Expressions; /* list of Expr */
 	List	   *ii_ExpressionsState;	/* list of ExprState */