On Jun 30, 2005, at 4:35 PM, markharw00d wrote:
Hi Erik,
Yes I was thinking that code could form the basis of a new
highlighter.
I've just attached a QuerySpansExtractor to the bugzilla entry for
the new highlighter. This class produces Spans from queries other
than SpanXxxxQueries eg phrase, term and booleans.
I'm thinking you can throw the text to be highligted as a single
doc into a MemIndex , extracts the spans using the
QuerySpansExtractor and the MemIndex's reader (need to expose a
getReader method on this - I'm working on it), then use some new
highlighting logic on the Spans.
Sound reasonable?
I think so.
One minor issue... a SpanNearQuery is not entirely equal to a
PhraseQuery when there is slop involved. You have this:
SpanNearQuery sp = new SpanNearQuery(clauses,query.getSlop
(),false);
Here's a test from Lucene in Action that demonstrates:
public void testSpanNearQuery() throws Exception {
SpanQuery[] quick_brown_dog =
new SpanQuery[]{quick, brown, dog};
SpanNearQuery snq =
new SpanNearQuery(quick_brown_dog, 0, true);
assertNoMatches(snq);
snq = new SpanNearQuery(quick_brown_dog, 4, true);
assertNoMatches(snq);
snq = new SpanNearQuery(quick_brown_dog, 5, true);
assertOnlyBrownFox(snq);
// interesting - even a sloppy phrase query would require
// more slop to match
snq = new SpanNearQuery(new SpanQuery[]{lazy, fox}, 3, false);
assertOnlyBrownFox(snq);
PhraseQuery pq = new PhraseQuery();
pq.add(new Term("f", "lazy"));
pq.add(new Term("f", "fox"));
pq.setSlop(4);
assertNoMatches(pq);
pq.setSlop(5);
assertOnlyBrownFox(pq);
}
So to be entirely accurate, an offset will be needed to get
SpanNearQuery to match PhraseQuery, though I have a feeling (I'm not
thinking through the details at the moment) that there is an edge
case or two that is not compatible. A PhraseQuery with slop of 1,
for example - can a SpanNearQuery be set up to match that exactly? I
don't think so... a PhraseQuery with slop of 1 cannot match in
reverse order, only in order with an optional hole between terms.
But, I like the idea of highlighting spans by converting other query
types to get the Spans.
Erik
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