From a2822fb9337a21f98ac4ce850bb4145acf47ca27 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 7 Oct 2011 20:13:02 -0400 Subject: 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. --- src/backend/optimizer/util/pathnode.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'src/backend/optimizer/util/pathnode.c') diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c index 4a1c94affb..8ed55a3d0e 100644 --- a/src/backend/optimizer/util/pathnode.c +++ b/src/backend/optimizer/util/pathnode.c @@ -25,8 +25,8 @@ #include "optimizer/paths.h" #include "optimizer/tlist.h" #include "parser/parsetree.h" -#include "utils/selfuncs.h" #include "utils/lsyscache.h" +#include "utils/selfuncs.h" static List *translate_sub_tlist(List *tlist, int relid); @@ -418,6 +418,7 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel) * 'indexscandir' is ForwardScanDirection or BackwardScanDirection * for an ordered index, or NoMovementScanDirection for * an unordered index. + * 'indexonly' is true if an index-only scan is wanted. * 'outer_rel' is the outer relation if this is a join inner indexscan path. * (pathkeys and indexscandir are ignored if so.) NULL if not. * @@ -430,6 +431,7 @@ create_index_path(PlannerInfo *root, List *indexorderbys, List *pathkeys, ScanDirection indexscandir, + bool indexonly, RelOptInfo *outer_rel) { IndexPath *pathnode = makeNode(IndexPath); @@ -468,6 +470,7 @@ create_index_path(PlannerInfo *root, pathnode->isjoininner = (outer_rel != NULL); pathnode->indexscandir = indexscandir; + pathnode->indexonly = indexonly; if (outer_rel != NULL) { @@ -506,7 +509,8 @@ create_index_path(PlannerInfo *root, pathnode->rows = rel->rows; } - cost_index(pathnode, root, index, indexquals, indexorderbys, outer_rel); + cost_index(pathnode, root, index, indexquals, indexorderbys, + indexonly, outer_rel); return pathnode; } -- cgit v1.2.1