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. --- doc/src/sgml/ref/postgres-ref.sgml | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'doc/src/sgml/ref/postgres-ref.sgml') diff --git a/doc/src/sgml/ref/postgres-ref.sgml b/doc/src/sgml/ref/postgres-ref.sgml index 3807f4090a8..9869a1f5262 100644 --- a/doc/src/sgml/ref/postgres-ref.sgml +++ b/doc/src/sgml/ref/postgres-ref.sgml @@ -376,12 +376,15 @@ PostgreSQL documentation - { s | i | m | n | h } + { s | i | o | b | t | n | m | h } Forbids the use of particular scan and join methods: s and i - disable sequential and index scans respectively, while + disable sequential and index scans respectively, + o, b and t + disable index-only scans, bitmap index scans, and TID scans + respectively, while n, m, and h disable nested-loop, merge and hash joins respectively. -- cgit v1.2.3