X-Git-Url: http://sigaev.ru/git/gitweb.cgi?p=plantuner.git;a=blobdiff_plain;f=README.plantuner;fp=README.plantuner;h=16aef5e48fc307ca82ff0f92bd29a500d0598952;hp=54c34f944fbef54aef87da8af686cad681df73b7;hb=4658687fa586302f46026d1405b36a3fdac87612;hpb=176da910e8225a413bac8992e650507f10f9b9d1

diff --git a/README.plantuner b/README.plantuner
index 54c34f9..16aef5e 100644
--- a/README.plantuner
+++ b/README.plantuner
@@ -1,15 +1,65 @@
-plantuner module provides plantuner.forbid_index GUC which contains comma-separated 
-list of indexes forbidden to use in query.
+Plantuner - enable planner hints
 
-USAGE (see sql/plantuner.sql:
-% LOAD 'plantuner';
-% SET plantuner.forbid_index="i_idx, j_idx";
-% SET enable_seqscan=off;
-% explain SELECT * FROM wow;
-                                QUERY PLAN                                
---------------------------------------------------------------------------
- Seq Scan on wow  (cost=10000000000.00..10000000031.40 rows=2140 width=8)
+contrib/plantuner is a contribution module for PostgreSQL 8.4+, which enable 
+planner hints.
 
+All work was done by Teodor Sigaev (teodor@sigaev.ru) and 
+ Oleg Bartunov (oleg@sai.msu.su).
+
+Sponsor: JFG Networks (www.jfg-networks.net)
+Motivation
+
+It's very interesting to be able to control planner (provide hints), which is 
+currently impossible. This first version of plantuner provides a possibility to
+hide specified indexes from PostgreSQL planner, so it will not use them.
+
+There are many situation, when developer want to temporarily disable specific 
+index(es), without dropping them, or to instruct planner to use specific index.
+Installation
+
+    * Get latest source of plantuner from CVS Repository
+    * gmake && gmake install && gmake installcheck
+
+Usage
+
+To enable the module you can either load shared library 'plantuner' in psql 
+session or specify 'shared_preload_libraries' option in postgresql.conf.
+
+=# LOAD 'plantuner';
+=# create table test(id int);
+=# create index id_idx on test(id);
+=# create index id_idx2 on test(id);
+=# \d test
+     Table "public.test"
+ Column |  Type   | Modifiers
+--------+---------+-----------
+ id     | integer |
+Indexes:
+    "id_idx" btree (id)
+    "id_idx2" btree (id)
+=# explain select id from test where id=1;
+                              QUERY PLAN
+-----------------------------------------------------------------------
+ Bitmap Heap Scan on test  (cost=4.34..15.03 rows=12 width=4)
+   Recheck Cond: (id = 1)
+   ->  Bitmap Index Scan on id_idx2  (cost=0.00..4.34 rows=12 width=0)
+         Index Cond: (id = 1)
+(4 rows)
+=# set enable_seqscan=off;
+=# set plantuner.forbid_index='id_idx2';
+=# explain select id from test where id=1;
+                              QUERY PLAN
+----------------------------------------------------------------------
+ Bitmap Heap Scan on test  (cost=4.34..15.03 rows=12 width=4)
+   Recheck Cond: (id = 1)
+   ->  Bitmap Index Scan on id_idx  (cost=0.00..4.34 rows=12 width=0)
+         Index Cond: (id = 1)
+(4 rows)
+=# set plantuner.forbid_index='id_idx2,id_idx';
+=# explain select id from test where id=1;
+                               QUERY PLAN
+-------------------------------------------------------------------------
+ Seq Scan on test  (cost=10000000000.00..10000000040.00 rows=12 width=4)
+   Filter: (id = 1)
+(2 rows)
 
-It's recommended to load library by shared_preload_libraries option
-in postgresql.conf