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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2011-10-07 20:13:02 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2011-10-07 20:14:13 -0400 |
| commit | a2822fb9337a21f98ac4ce850bb4145acf47ca27 (patch) | |
| tree | c239fe9a32ff0225e906711a76348cee1567f0d8 /doc/src/sgml/ref/postgres-ref.sgml | |
| parent | caa1054df8408b165e5f66ff25c87b6dd0a0a1e7 (diff) | |
| download | postgresql-a2822fb9337a21f98ac4ce850bb4145acf47ca27.tar.gz postgresql-a2822fb9337a21f98ac4ce850bb4145acf47ca27.zip | |
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.
Diffstat (limited to 'doc/src/sgml/ref/postgres-ref.sgml')
| -rw-r--r-- | doc/src/sgml/ref/postgres-ref.sgml | 7 |
1 files changed, 5 insertions, 2 deletions
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 <variablelist> <varlistentry> - <term><option>-f</option> <literal>{ s | i | m | n | h }</literal></term> + <term><option>-f</option> <literal>{ s | i | o | b | t | n | m | h }</literal></term> <listitem> <para> Forbids the use of particular scan and join methods: <literal>s</literal> and <literal>i</literal> - disable sequential and index scans respectively, while + disable sequential and index scans respectively, + <literal>o</literal>, <literal>b</literal> and <literal>t</literal> + disable index-only scans, bitmap index scans, and TID scans + respectively, while <literal>n</literal>, <literal>m</literal>, and <literal>h</literal> disable nested-loop, merge and hash joins respectively. </para> |