Re: default_text_search_config and expression indexes

On Tue, 31 Jul 2007, Bruce Momjian wrote:

>>> And if we have to require the configuration name in CREATE INDEX, it has
>>> to be used in WHERE, so we might as well just remove the default
>>> capability and always require the configuration name.
>>
>> this is very rare use case for text searching
>> 1. expression index without configuration name
>> 2. default_text_search_config can be changed by somebody
>
> If you are going to be using the configuration name with the create
> expression index, you have to use it in the WHERE clause (or the index
> doesn't work), and I assume that is 90% of the text search uses.  I
> don't see it as rare at all.

What is a basis of your assumption ? In my opinion, it's very limited
use of text search, because it doesn't supports ranking. For 4-5 years
of tsearch2 usage I never used it and I never seem in mailing lists.
This is very user-oriented feature and we could probably ask 
-general people for their opinion.

>> If somebody really need it, then he should be adviced to use configuration
>> name, else we don't guarantee that somebody could change
>> default_text_search_config  variable and this could lead to
>> incorrect dump/restore.
>>
>> I don't think we should remove default_text_search_config because of
>> this rare case.
>
> I still feel the default_text_search_config has to be removed.  We have
> tried all sorts of ways to make it work but having it not be 100%
> reliable for pg_dump/restore means it might as well be in /contrib and
> unsupported.  If we have it in core, it has to work 100%.  We can't have
> tons of examples that don't specify the configuration name and then
> expect every create expression index and WHERE clause to use it.
> default_text_search_config _can_ work, but it seems so easy to break and
> so easy to get wrong that I think it must be removed.

I'd better say we don't support text searching using expression index
than remove default_text_search_config. Anyway, I don't feel myself
responisble for such important problem. We need more feedback from 
users.

>
> If we are going to keep it, I need someone to explain why my comments
> above are wrong.  If I am right, someone has to remove
> default_text_search_config from the patch.   I can do the documentation.

I'm in conference and then will be busy writing my applications and
earning money, Teodor is in vacation. I don't want to do 
hasty conclusion, since we're very tired to change our patch from 
one solution to another. We need consensus of developers and users.
I'm almost exhausted and have  no time  to continue this discussion.

Would you be so kind to write separate post about this problem and
call -hackers and -general for feedback. Let's experienced users
show their needs. We said everything and has nothing to add.

	Regards,		Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83