Support index-only scans using the visibility map to avoid heap fetches.

When a btree index contains all columns required by the query, and the
visibility map shows that all tuples on a target heap page are
visible-to-all, we don't need to fetch that heap page.  This patch depends
on the previous patches that made the visibility map reliable.

There's a fair amount left to do here, notably trying to figure out a less
chintzy way of estimating the cost of an index-only scan, but the core
functionality seems ready to commit.

Robert Haas and Ibrar Ahmed, with some previous work by Heikki Linnakangas.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/include/optimizer/var.h b/src/include/optimizer/var.h
index 5d7e2d93e91..4fd0052f2df 100644
--- a/src/include/optimizer/var.h
+++ b/src/include/optimizer/var.h
@@ -31,7 +31,7 @@ typedef enum
 } PVCPlaceHolderBehavior;
 
 extern Relids pull_varnos(Node *node);
-extern void pull_varattnos(Node *node, Bitmapset **varattnos);
+extern void pull_varattnos(Node *node, Index varno, Bitmapset **varattnos);
 extern bool contain_var_clause(Node *node);
 extern bool contain_vars_of_level(Node *node, int levelsup);
 extern int	locate_var_of_level(Node *node, int levelsup);