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https://issues.apache.org/jira/browse/LUCENE-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14248188#comment-14248188
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Robert Muir commented on LUCENE-2878:
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Hi Alan,
Why are there now additional branches in nextPosition() in posting readers? Can
we avoid these? If it is to support calling nextPosition() after it has already
been exhausted, I am unsure we should be doing this. nextDoc() does not support
this, for example.
Can we improve this logic in reuse code? Reuse code is notorious for sneaky
bugs, and I don't like the comparison done here. Why can't we just check if the
bit is set?
{code}
if ((flags & DocsEnum.FLAG_POSITIONS) >= DocsEnum.FLAG_POSITIONS)
{code}
This check also is confusing to me in the first place. Why do we have both
docsEnum and docsAndPositionsEnum methods, both returning DocsEnum, with the
former checking for a FLAG_POSITIONS and calling the other one in that case. I
think there should just be one method instead if we want both to share the same
api, thats ok.
TermScorer introduces outdated dead code that is unused.
What are the Span scoring classes still doing here?
Do we have tests for any of this new code? I see no added tests files.
What about benchmarks? We should try to compare against trunk, since there are
a lot of change here.
In general, I can try to make a patch for smaller things, to make things
faster. Iterating this way may take a long time.
> Allow Scorer to expose positions and payloads aka. nuke spans
> --------------------------------------------------------------
>
> Key: LUCENE-2878
> URL: https://issues.apache.org/jira/browse/LUCENE-2878
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/search
> Affects Versions: Positions Branch
> Reporter: Simon Willnauer
> Assignee: Robert Muir
> Labels: gsoc2014
> Fix For: Positions Branch
>
> Attachments: LUCENE-2878-OR.patch, LUCENE-2878-vs-trunk.patch,
> LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch,
> LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch,
> LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch,
> LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch,
> LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch,
> LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch,
> LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch,
> LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878_trunk.patch,
> LUCENE-2878_trunk.patch, PosHighlighter.patch, PosHighlighter.patch
>
>
> Currently we have two somewhat separate types of queries, the one which can
> make use of positions (mainly spans) and payloads (spans). Yet Span*Query
> doesn't really do scoring comparable to what other queries do and at the end
> of the day they are duplicating lot of code all over lucene. Span*Queries are
> also limited to other Span*Query instances such that you can not use a
> TermQuery or a BooleanQuery with SpanNear or anthing like that.
> Beside of the Span*Query limitation other queries lacking a quiet interesting
> feature since they can not score based on term proximity since scores doesn't
> expose any positional information. All those problems bugged me for a while
> now so I stared working on that using the bulkpostings API. I would have done
> that first cut on trunk but TermScorer is working on BlockReader that do not
> expose positions while the one in this branch does. I started adding a new
> Positions class which users can pull from a scorer, to prevent unnecessary
> positions enums I added ScorerContext#needsPositions and eventually
> Scorere#needsPayloads to create the corresponding enum on demand. Yet,
> currently only TermQuery / TermScorer implements this API and other simply
> return null instead.
> To show that the API really works and our BulkPostings work fine too with
> positions I cut over TermSpanQuery to use a TermScorer under the hood and
> nuked TermSpans entirely. A nice sideeffect of this was that the Position
> BulkReading implementation got some exercise which now :) work all with
> positions while Payloads for bulkreading are kind of experimental in the
> patch and those only work with Standard codec.
> So all spans now work on top of TermScorer ( I truly hate spans since today )
> including the ones that need Payloads (StandardCodec ONLY)!! I didn't bother
> to implement the other codecs yet since I want to get feedback on the API and
> on this first cut before I go one with it. I will upload the corresponding
> patch in a minute.
> I also had to cut over SpanQuery.getSpans(IR) to
> SpanQuery.getSpans(AtomicReaderContext) which I should probably do on trunk
> first but after that pain today I need a break first :).
> The patch passes all core tests
> (org.apache.lucene.search.highlight.HighlighterTest still fails but I didn't
> look into the MemoryIndex BulkPostings API yet)
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