Re: tsearch2 dictionary for statute cites

On Tue, 10 Mar 2009, Tom Lane wrote:

> "Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
>> People are likely to search for statute cites, which tend to have a
>> hierarchical form.  I'm not sure the prefix approach will work for
>> this.  For example, there is a section 939.64 in the state statutes
>> dealing with commission of a crime while wearing a bulletproof
>> garment.  If someone searches for that, they should find subsections
>> like 939.64(1) or 939.64(2) but not different sections which start
>> with the same characters like 939.641 (the section on concealing
>> identity) or 939.645 (the section on hate crimes).  A search for
>> chapter 939 should return any of the above.
>
> I think what you need is a custom parser that treats these similarly to
> hyphenated words.  If I pretend that the dot is a hyphen I get matching
> behavior that seems to meet all those requirements.
>
> Unfortunately we don't seem to have any really easy way to plug in a
> custom parser, other than copy-paste-modify the existing one which would
> be a PITA from a maintenance standpoint.  Perhaps you could pass the
> texts and the queries through a regexp substitution that converts
> digit-dot-digit to digit-dash-digit?

perhaps, for 8.4 it's better to utilize prefix search, like
to_tsquery('939.645:*') will find what Kevin need. The problem is with
parser, so I'd preprocess text before indexing to convert all
digit.digit(digit) to digit.digit.digit, which is what parser recognizes as
a single lexem 'version'.  Here is just an illustration

qq=# select * from ts_parse('default',translate('939.64(1)','()','. '));
  tokid |  token
-------+----------
      8 | 939.64.1
     12 |

btw, having 'version' it's possible to use dict_regex for 8.3.


>
>             regards, tom lane
>
>

     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