matching only empty fields

[Lukas Kahwe Smith <ml...@pooteeweet.org>]

Hi,

I have implemented a facet search, where users essentially select what should not be included. I do this by constructing an fq filter where I match for the deselected items that I then negate:
            $fq = "{!tag=dt}!($fq)";
            $criteria->addParam('fq', $fq);

Now in some cases the field the user is deselecting is actually an empty string.

For example go to the below address and open the "legal value" section. there is an option "none" there, which is actually an empty string.
http://search.un-informed.org/search?q=malaria&=&tm=any&s=Search

The field itself is just an untokenized string. Of course I could just turn an empty string into "none" at index time, but I am wondering how to do it in general :)

I tried using just "" or ["" TO ""] to match for empty strings, but this matches everything and due to the negation removes everything.

regards,
Lukas Kahwe Smith
mls@pooteeweet.org

Re: matching only empty fields

[Yonik Seeley <yo...@lucidimagination.com>]

On Sat, May 29, 2010 at 10:01 AM, Lukas Kahwe Smith <ml...@pooteeweet.org> wrote:
> Hi,
>
> I have implemented a facet search, where users essentially select what should not be included. I do this by constructing an fq filter where I match for the deselected items that I then negate:
>            $fq = "{!tag=dt}!($fq)";
>            $criteria->addParam('fq', $fq);
>
> Now in some cases the field the user is deselecting is actually an empty string.
>
> For example go to the below address and open the "legal value" section. there is an option "none" there, which is actually an empty string.
> http://search.un-informed.org/search?q=malaria&=&tm=any&s=Search
>
> The field itself is just an untokenized string. Of course I could just turn an empty string into "none" at index time, but I am wondering how to do it in general :)
>
> I tried using just "" or ["" TO ""] to match for empty strings, but this matches everything and due to the negation removes everything.

Hmmm, if this is on a String field, it seemed to work for me.
http://localhost:8983/solr/select?debugQuery=on&q=foo_s:""

The raw query parser would also work (it skips analysis):
http://localhost:8983/solr/select?debugQuery=on&q={!raw f=foo_s}

But yes, indexing differently may be easier for you... either by
indexing a special token for _NONE_
or by leaving out the value completely (not indexing it), and using
facet.missing=true and filtering for none via fq=-myfield:[* TO *]

-Yonik
http://www.lucidimagination.com