Add scripts to enable/disable use of new LIKE/regexp selectivity

estimation operators.  See contrib/likeplanning/README for info.

contrib/README

@@ -35,6 +35,12 @@ isbn_issn -
 	PostgreSQL type extensions for ISBN (books) and ISSN (serials)
 	by Garrett A. Wollman <wollman@khavrinen.lcs.mit.edu>
 
+likeplanning -
+	Scripts to enable/disable new planning code for LIKE and regexp
+	pattern match operators.  These will go away again once the code
+	is mature enough to enable by default.
+	by Tom Lane <tgl@sss.pgh.pa.us>
+
 linux -
 	Start postgres back end system
 	by Thomas Lockhart <lockhart@alumni.caltech.edu>

contrib/likeplanning/README

+This directory contains three SQL scripts that control use of some new
+code for planning/optimizing queries containing LIKE and
+regular-expression operators.  This code was added to Postgres 7.0 late in
+beta test, and it hasn't gotten enough testing to warrant turning it on by
+default in release 7.0 (although it probably will become default in 7.1).
+So, here are some scripts to enable and disable it.  You may want to run
+these scripts if you have problems with the planner choosing bad plans for
+queries involving LIKE or regexps in WHERE clauses.
+
+
+HOW TO USE THE SCRIPTS
+----------------------
+
+All three scripts must be run as the Postgres superuser.  The easiest
+way to run an SQL script is
+	psql -f scriptfile databasename
+or you can start psql interactively and enter
+	\i scriptfile
+
+enablelike.sql enables use of the new planning code in the database in
+which it is run.  If you run it in template1, all subsequently-created
+databases will use the new code by default.
+
+disablelike.sql reverts to the old planning code for LIKE, in the database
+in which it is run.  If you run it in template1, all subsequently-created
+databases will use the old code by default.
+
+If your database was initdb'd with release 7.0beta5, you need to run
+updatepgproc.sql before you can run enablelike.sql.  Databases initdb'd
+with 7.0RC1 or later already have pg_proc entries for the new code, so
+updatepgproc.sql is unnecessary for them.  If enablelike.sql produces
+errors like "No procedure with name regexeqsel", then you need to run
+updatepgproc.sql.
+
+
+WHAT IT DOES
+------------
+
+These scripts install (or disable) new code for "selectivity estimation"
+of LIKE and regexp operators.  Selectivity estimation determines the
+estimated number of rows produced by a query or subquery, and that in turn
+determines the kind of plan the planner will use.  The old selectivity
+estimator ignored the pattern being searched for and just produced the
+same estimate as for an "=" operator, which of course was usually too low
+for a wildcard match.  The new code has some knowledge of pattern matching
+rules and generates an estimate based on the number of fixed characters and
+wildcards present in the pattern.  Also, if the pattern has a fixed prefix
+that must be matched (such as LIKE 'foo%' or ~ '^foo'), an appropriate
+range-query selectivity estimate is produced and factored into the result.
+
+If you want to look at the code itself, see src/backend/utils/adt/selfuncs.c.

contrib/likeplanning/disablelike.sql

+-- This script disables use of the new LIKE-related selectivity estimation
+-- functions, which are a little too new to be enabled by default in 7.0.
+-- You can enable them again by running enablelike.sql.
+
+-- Use of the functions will be disabled only in those databases you
+-- run this script in.  If you run it in template1,
+-- all subsequently-created databases will not use the functions.
+
+-- Be sure to run the script as the Postgres superuser!
+
+UPDATE pg_operator SET
+	oprrest = 'eqsel'::regproc,
+	oprjoin = 'eqjoinsel'::regproc
+WHERE oprrest = 'regexeqsel'::regproc;
+
+UPDATE pg_operator SET
+	oprrest = 'eqsel'::regproc,
+	oprjoin = 'eqjoinsel'::regproc
+WHERE oprrest = 'icregexeqsel'::regproc;
+
+UPDATE pg_operator SET
+	oprrest = 'eqsel'::regproc,
+	oprjoin = 'eqjoinsel'::regproc
+WHERE oprrest = 'likesel'::regproc;
+
+UPDATE pg_operator SET
+	oprrest = 'neqsel'::regproc,
+	oprjoin = 'neqjoinsel'::regproc
+WHERE oprrest = 'regexnesel'::regproc;
+
+UPDATE pg_operator SET
+	oprrest = 'neqsel'::regproc,
+	oprjoin = 'neqjoinsel'::regproc
+WHERE oprrest = 'icregexnesel'::regproc;
+
+UPDATE pg_operator SET
+	oprrest = 'neqsel'::regproc,
+	oprjoin = 'neqjoinsel'::regproc
+WHERE oprrest = 'nlikesel'::regproc;

contrib/likeplanning/enablelike.sql

+-- This script enables use of the new LIKE-related selectivity estimation
+-- functions, which are a little too new to be enabled by default in 7.0.
+-- You can disable them again by running disablelike.sql.
+
+-- If your database was initdb'd with 7.0beta5, you need to run
+-- updatepgproc.sql first.  You can tell that is necessary if this
+-- script produces errors like "No procedure with name regexeqsel".
+
+-- Use of the functions will be enabled only in those databases you
+-- run this script in.  If you run it in template1,
+-- all subsequently-created databases will use the functions.
+
+-- Be sure to run the script as the Postgres superuser!
+
+UPDATE pg_operator SET
+	oprrest = 'regexeqsel'::regproc,
+	oprjoin = 'regexeqjoinsel'::regproc
+WHERE oprrest = 'eqsel'::regproc AND oprname = '~';
+
+UPDATE pg_operator SET
+	oprrest = 'icregexeqsel'::regproc,
+	oprjoin = 'icregexeqjoinsel'::regproc
+WHERE oprrest = 'eqsel'::regproc AND oprname = '~*';
+
+UPDATE pg_operator SET
+	oprrest = 'likesel'::regproc,
+	oprjoin = 'likejoinsel'::regproc
+WHERE oprrest = 'eqsel'::regproc AND oprname = '~~';
+
+UPDATE pg_operator SET
+	oprrest = 'regexnesel'::regproc,
+	oprjoin = 'regexnejoinsel'::regproc
+WHERE oprrest = 'neqsel'::regproc AND oprname = '!~';
+
+UPDATE pg_operator SET
+	oprrest = 'icregexnesel'::regproc,
+	oprjoin = 'icregexnejoinsel'::regproc
+WHERE oprrest = 'neqsel'::regproc AND oprname = '!~*';
+
+UPDATE pg_operator SET
+	oprrest = 'nlikesel'::regproc,
+	oprjoin = 'nlikejoinsel'::regproc
+WHERE oprrest = 'neqsel'::regproc AND oprname = '!~~';

contrib/likeplanning/updatepgproc.sql

+-- This script loads pg_proc entries for the 7.0 selectivity estimation
+-- functions into a 7.0beta5 database.  You should not run it if you
+-- initdb'd with 7.0RC1 or later.  If you do need it, run it in each
+-- database you have, including template1.  Once you have run it in
+-- template1, all subsequently-created databases will contain the entries,
+-- so you won't need to run it again.
+-- Be sure to run the script as the Postgres superuser!
+
+COPY pg_proc WITH OIDS FROM stdin;
+1818	regexeqsel	0	11	f	t	f	5	f	701	26 26 21 0 23	100	0	0	100	regexeqsel	-
+1819	likesel	0	11	f	t	f	5	f	701	26 26 21 0 23	100	0	0	100	likesel	-
+1820	icregexeqsel	0	11	f	t	f	5	f	701	26 26 21 0 23	100	0	0	100	icregexeqsel	-
+1821	regexnesel	0	11	f	t	f	5	f	701	26 26 21 0 23	100	0	0	100	regexnesel	-
+1822	nlikesel	0	11	f	t	f	5	f	701	26 26 21 0 23	100	0	0	100	nlikesel	-
+1823	icregexnesel	0	11	f	t	f	5	f	701	26 26 21 0 23	100	0	0	100	icregexnesel	-
+1824	regexeqjoinsel	0	11	f	t	f	5	f	701	26 26 21 26 21	100	0	0	100	regexeqjoinsel	-
+1825	likejoinsel	0	11	f	t	f	5	f	701	26 26 21 26 21	100	0	0	100	likejoinsel	-
+1826	icregexeqjoinsel	0	11	f	t	f	5	f	701	26 26 21 26 21	100	0	0	100	icregexeqjoinsel	-
+1827	regexnejoinsel	0	11	f	t	f	5	f	701	26 26 21 26 21	100	0	0	100	regexnejoinsel	-
+1828	nlikejoinsel	0	11	f	t	f	5	f	701	26 26 21 26 21	100	0	0	100	nlikejoinsel	-
+1829	icregexnejoinsel	0	11	f	t	f	5	f	701	26 26 21 26 21	100	0	0	100	icregexnejoinsel	-
+\.
+
+UPDATE pg_proc SET proowner = pg_shadow.usesysid
+WHERE oid >= 1818 AND oid <= 1829 AND pg_shadow.usename = CURRENT_USER;