CREATE INDEX ... INCLUDING (column[, ...])

Now indexes (but only B-tree for now) can contain "extra" column(s) which
doesn't participate in index structure, they are just stored in leaf
tuples. It allows to use index only scan by using single index instead
of two or more indexes.

Author: Anastasia Lubennikova with minor editorializing by me
Reviewers: David Rowley, Peter Geoghegan, Jeff Janes

1 files changed, 31 insertions, 0 deletions

diff --git a/src/backend/access/common/indextuple.c b/src/backend/access/common/indextuple.c
index 274a6c2e702..8884c1e56c4 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"
 
 
 /* ----------------------------------------------------------------
@@ -441,3 +442,33 @@ CopyIndexTuple(IndexTuple source)
 	memcpy(result, source, size);
 	return result;
 }
+
+/*
+ * Reform index tuple. Truncate nonkey (INCLUDING) attributes.
+ */
+IndexTuple
+index_truncate_tuple(Relation idxrel, IndexTuple olditup)
+{
+	TupleDesc   itupdesc = RelationGetDescr(idxrel);
+	Datum       values[INDEX_MAX_KEYS];
+	bool        isnull[INDEX_MAX_KEYS];
+	IndexTuple	newitup;
+	int indnatts = IndexRelationGetNumberOfAttributes(idxrel);
+	int indnkeyatts = IndexRelationGetNumberOfKeyAttributes(idxrel);
+
+	Assert(indnatts <= INDEX_MAX_KEYS);
+	Assert(indnkeyatts > 0);
+	Assert(indnkeyatts < indnatts);
+
+	index_deform_tuple(olditup, itupdesc, values, isnull);
+
+	/* form new tuple that will contain only key attributes */
+	itupdesc->natts = indnkeyatts;
+	newitup = index_form_tuple(itupdesc, values, isnull);
+	newitup->t_tid = olditup->t_tid;
+
+	itupdesc->natts = indnatts;
+
+	Assert(IndexTupleSize(newitup) <= IndexTupleSize(olditup));
+	return newitup;
+}