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, 31 insertions, 0 deletions

diff --git a/src/backend/access/common/indextuple.c b/src/backend/access/common/indextuple.c
index f7103e53bcc..a9c0b620ec0 100644
--- a/src/backend/access/common/indextuple.c
+++ b/src/backend/access/common/indextuple.c
@@ -19,6 +19,7 @@
 #include "access/heapam.h"
 #include "access/itup.h"
 #include "access/tuptoaster.h"
+#include "utils/rel.h"
 
 
 /* ----------------------------------------------------------------
@@ -445,3 +446,33 @@ CopyIndexTuple(IndexTuple source)
 	memcpy(result, source, size);
 	return result;
 }
+
+/*
+ * Truncate tailing attributes from given index tuple leaving it with
+ * new_indnatts number of attributes.
+ */
+IndexTuple
+index_truncate_tuple(TupleDesc tupleDescriptor, IndexTuple olditup,
+					 int new_indnatts)
+{
+	TupleDesc	itupdesc = CreateTupleDescCopyConstr(tupleDescriptor);
+	Datum		values[INDEX_MAX_KEYS];
+	bool		isnull[INDEX_MAX_KEYS];
+	IndexTuple	newitup;
+	int			indnatts = tupleDescriptor->natts;
+
+	Assert(indnatts <= INDEX_MAX_KEYS);
+	Assert(new_indnatts > 0);
+	Assert(new_indnatts < indnatts);
+
+	index_deform_tuple(olditup, tupleDescriptor, values, isnull);
+
+	/* form new tuple that will contain only key attributes */
+	itupdesc->natts = new_indnatts;
+	newitup = index_form_tuple(itupdesc, values, isnull);
+	newitup->t_tid = olditup->t_tid;
+
+	FreeTupleDesc(itupdesc);
+	Assert(IndexTupleSize(newitup) <= IndexTupleSize(olditup));
+	return newitup;
+}