Re: default_text_search_config and expression indexes

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

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