Traktormaster commented on a change in pull request #1123: LUCENE-9093: Unified
highlighter with word separator never gives context to the left
URL: https://github.com/apache/lucene-solr/pull/1123#discussion_r361650672
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File path:
lucene/highlighter/src/java/org/apache/lucene/search/uhighlight/LengthGoalBreakIterator.java
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@@ -174,7 +175,48 @@ private int moveToBreak(int idx) { // precondition: idx
is a known break
// called at start of new Passage given first word start offset
@Override
public int preceding(int offset) {
- return baseIter.preceding(offset); // no change needed
+ final int fragmentStart = Math.max(baseIter.preceding(offset), 0); //
convert DONE to 0
+ fragmentEndFromPreceding = baseIter.following(fragmentStart);
+ if (fragmentEndFromPreceding == DONE) {
+ fragmentEndFromPreceding = baseIter.last();
+ }
+ final int centerLength = fragmentEndFromPreceding - fragmentStart;
+ final int extraPrecedingLengthGoal = (int)((lengthGoal - centerLength) *
fragmentAlignment);
Review comment:
I have a working version with this new behavior. There is just a single
assertion that fails
[here](https://github.com/apache/lucene-solr/blob/e06ad4cfb587e1bb69a80c0b531df0e52c2da89b/solr/core/src/test/org/apache/solr/highlight/TestUnifiedSolrHighlighter.java#L267).
It's because the `fragsize=60` there means to try and get 60 characters on the
right side of the match as the default `fragalign` is zero. To pass the test
the query parameters need to be changed to have
`hl.fragsize=50&hl.fragalign=0.5`.
This is not a problem by itself, but there is no way to make the new
behavior completely backwards-compatible like the previous one.
It could also be a bit jarring to have `fragsize` with a distinctively
different meaning compared to the other highlighters:
- For original&fastVector the `fragsize` is the target size of the snippet.
- For unified the `fragsize` is the size of the contextual text around the
match. Ie.: the snippet's target size is `fragsize+matchsize`.
I'm still in favor of this change, there's literally half as many calls to
`preceding()` and `following()` of the underlying BI and it's much clearer as
well.
Should I change the failing test and push this for review? What about the
backward-compatibility? I'm not sure how to change the docs or the default
parameters.
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