1) If you set the default slop factor in QueryProcessor to something greater
than 1, can you also use wildcards? (I ask that question because, to my
understanding, you can't combine the explicit proximity query syntax with
wildcards. That is, something like "quick fox*"~3 is not legal.)
Wildcard queries and phrase queries are completely different entities with QueryParser. The default slop factor has no relation to wildcard queries whatsoever.
"quick fox*"~3 is legal, technically. But it analyzes "quick fox" (probably into "quick" and "fox", dropping the asterisk) and then uses a slop of 3. Specifying the slop explicitly overrides the default value.
If you want something that does "quick fox*" where "quick" must be followed by something starting with "fox", you'll have to do this through the API, perhaps using the awkwardly named PhrasePrefixQuery, which does support slop also. It would be up to you to do the term expansions for all terms beginning with "fox" in order to use this.
2) Regarding the SpanQuery family, do we have any documentation on (a) what
led to their emergence (what problem they solve), (b) what their syntax is
(other than what can be discerned from the JUnit tests), and (c) examples of
their use?
The unit tests are always my first stop :)
Span queries allow you to say things like:
"foo bar" near "xyz pdq"
all docs that have "foo bar" within 10 positions in order (which you cannot do with phrase query)
all docs that have "foo bar" within 10 positions but within that span it may not have "baz"
all docs that have "foo" in the first 3 positions of the field
None of these are possible without this new span feature.
3) Is there a plan for adding QueryParser support for the SpanQuery family?
I think QueryParser is overloaded enough. It is pretty simple to have phrase queries turned into span queries with a QueryParser subclass, forcing terms to be in order:
/**
* Replace PhraseQuery with SpanNearQuery to force in-order
* phrase matching rather than reverse.
*/
protected Query getFieldQuery(
String field, Analyzer analyzer, String queryText, int slop)
throws ParseException {
// let QueryParser's implementation do the analysis
Query orig = super.getFieldQuery(
field, analyzer, queryText, slop); if (! (orig instanceof PhraseQuery)) {
return orig;
} PhraseQuery pq = (PhraseQuery) orig;
Term[] terms = pq.getTerms();
SpanTermQuery[] clauses = new SpanTermQuery[terms.length];
for (int i = 0; i < terms.length; i++) {
clauses[i] = new SpanTermQuery(terms[i]);
} SpanNearQuery query = new SpanNearQuery(
clauses, slop, true);return query; }
I built this example for Lucene in Action recently.
Erik
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