Statistics example query gives no hits if some attribute value is empty

[arildm]

Steps to reproduce:

1. Make a statistics search
2. Group by word and some variable that gives empty values, like name
3. Click a cell with a count higher than 0 to open an example KWIC search
4. Expected: Get the same number of hits
5. Actual: No hits

Example: https://spraakbanken.gu.se/korp/#?search=word%7Cgod&corpus=attasidor&prefix&result_tab=2&stats_reduce=word,ne_name

When deselecting word from the group-by selector, there's an error instead: CQPError: Malformed input string passed to builtin ambiguity(i god tid). Maybe that's another bug.

[arildm]

@MartinHammarstedt Could you check if the params sent in the /query request are reasonable? I guess especially cqp2: <match> [word = 'godis' & ambiguity(_.ne_name) = 0] []{0,} </match>

[arildm]

The ambiguity(_.ne_name) = 0 part is obviously wrong. That only works for set-type positional attributes. There's no problem with complemgram for instance: https://spraakbanken.gu.se/korp/#?search=word%7Cgod&corpus=attasidor&prefix&result_tab=2&stats_reduce=word,complemgram

For single-value positional attributes we can use <attr> = "". But how do we match tokens that have no ne_name value?
@MartinHammarstedt

Edit: ambiguity() can be used with non-set-type attributes too

[MartinHammarstedt]

ambiguity() should only work for sets, and it works for both positional and structural attributes. But it doesn't mean "not contained by structure", which is what we need for the ne annotation in this case. To say "not contained by <ne_name>", use [word = 'godis' & !ne_name].

The next question is, how do you determine from the /count result if a structural attribute is empty but present, or if it's not present at all? I don't think you can. Maybe you have to resort to (!ne_name | _.ne_name='').