Skip site navigation (1) Skip section navigation (2)

Re: default_text_search_config and expression indexes

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Magnus Hagander <magnus(at)hagander(dot)net>
Cc: Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Michael Paesold <mpaesold(at)gmx(dot)at>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, Teodor Sigaev <teodor(at)sigaev(dot)ru>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: default_text_search_config and expression indexes
Date: 2007-07-28 01:22:21
Message-ID: 200707280122.l6S1ML213868@momjian.us (view raw or flat)
Thread:
Lists: pgsql-advocacypgsql-hackers
Magnus Hagander wrote:
> > However, the big problem is that the expressions used in expression
> > indexes should not change their output based on the value of a GUC
> > variable (because it would corrupt the index), but in the case above,
> > default_text_search_config controls what configuration is used, and
> > hence the output of to_tsvector is changed if default_text_search_config
> > changes.
> 
> It wuoldn't actually *corrupt* the index, right? You could end up with
> wrong results, which might be regarded as corruption in one way, but as
> long as you change the value back the index still works, no?

Right, it would _temporarily_ corrupt it.  ;-)

> > We have a few possible options:
> > 
> > 	1) Document the problem and do nothing else.
> > 	2) Make default_text_search_config a postgresql.conf-only
> > 	   setting, thereby making it impossible to change by non-super
> > 	   users, or make it a super-user-only setting.
> > 	3) Remove default_text_search_config and require the
> > 	   configuration to be specified in each function call.
> > 
> > If we remove default_text_search_config, it would also make ::tsvector
> > casting useless as well.
> 
> I think 3 is a really bad solution.
> 
> 2 is a half-bad solution. Do we have a way to say that it can be set at
> database-level for example, but not at user session? Making it
> superuser-only to change it but not postgresql.conf-only could accomplish
> that, along with warnings in the docs for the super user about the effects
> on current indexes by changing it.

OK, here is what I am thinking.  If we make default_text_search_config
super-user-only, then the user can't do SET (using "zero_damaged_pages"
as a superuser-only example):

	test=> set zero_damaged_pages = on;
	ERROR:  permission denied to set parameter "zero_damaged_pages"
	
	test=> alter user guest set zero_damaged_pages = on;
	ERROR:  permission denied to set parameter "zero_damaged_pages"

but the super-user can set it in postgresql.conf, or:

	test=# alter user guest set zero_damaged_pages = on;
	ALTER ROLE

or

	test=# alter database vendor3 set zero_damaged_pages = on;
	ALTER ROLE

meaning while it will be super-user-only, the administrator can set the
default for specific databases and users.  Is that the best approach?

A user can still over-ride the default by specifying the configuration
in the function call.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>          http://momjian.us
  EnterpriseDB                               http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

In response to

Responses

pgsql-hackers by date

Next:From: algattDate: 2007-07-28 07:13:39
Subject: New Index
Previous:From: Jim NasbyDate: 2007-07-27 23:45:34
Subject: Re: stats_block_level

pgsql-advocacy by date

Next:From: Chris BellDate: 2007-07-28 03:32:27
Subject: Re: mysql community miserable about OSCON 2007
Previous:From: Joshua D. DrakeDate: 2007-07-28 01:11:48
Subject: Re: [GENERAL] PostgreSQL, PGDAY, PGParty and OSCON 2007 Rocked!

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group