Re: Updated tsearch documentation - Mailing list pgsql-hackers

On Tue, 17 Jul 2007, Bruce Momjian wrote:

> I think the tsearch documentation is nearing completion:
>
>     http://momjian.us/expire/fulltext/HTML/textsearch.html
>
> but I am not happy with how tsearch is enabled in a user table:
>
>     http://momjian.us/expire/fulltext/HTML/textsearch-app-tutorial.html
>
> Aside from the fact that it needs more examples, it only illustrates an
> example where someone creates a table, populates it, then adds a
> tsvector column, populates that, then creates an index.
>
> That seems quite inflexible.  Is there a way to avoid having a separate
> tsvector column?  What happens if the table is dynamic?  How is that
> column updated based on table changes?  Triggers?  Where are the
> examples?  Can you create an index like this:

I agree, that there are could be more examples, but text search doesn't
require something special !
*Example* of trigger function is documented on 
http://momjian.us/expire/fulltext/HTML/textsearch-opfunc.html


>
>     CREATE INDEX textsearch_id ON pgweb USING gin(to_tsvector(column));
>
> That avoids having to have a separate column because you can just say:
>
>     WHERE to_query('XXX') @@ to_tsvector(column)

yes, it's possible, but without ranking, since currently it's impossible 
to store any information in index (it's pg's feature). btw, this should
works and for GiST index also.

That kind of search is useful if there is  another natural ordering of search 
results, for example, by timestamp.

>
> How do we make sure that the to_query is using the same text search
> configuration as the 'column' or index?  Perhaps we should suggest:

please, keep in mind, it's not mandatory to use the same configuration
at search time, that was used at index creation.

>
>  CREATE INDEX textsearch_idx ON pgweb USING gin(to_tsvector('english',column));
>
> so that at least the configuration is documented in the index.

yes, it's better to always explicitly specify configuration name and not 
rely on default configuration. 
Unfortunately, configuration name doesn't saved in the index.
    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