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From "Simon Willnauer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-2878) Allow Scorer to expose positions and payloads aka. nuke spans
Date Sun, 11 Nov 2012 13:09:13 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13494874#comment-13494874
] 

Simon Willnauer commented on LUCENE-2878:
-----------------------------------------

hey alan,

bq. I've started to use this branch in an (experimental!) system I'm developing for a client.


very good news! cool stuff - can you provide more infos what you are doing there? Do you highlight
too?

regarding your latest patch - commit it!

bq. 1) There isn't a replacement for SpanNotQueries - the BrouwerianIterator comes close,
but doesn't quite cover all the use cases. I
can you provide a testcase what it doesn't cover? you can go ahead and commit it even if you
don't have a fix.

bq. 2) The API is not very nice when it comes to subclassing Iterators. For example, I have
'anchor' terms at the start and end of documents, which allow 
 
I am not sure I understand this. if you have marker terms how do they differ from ordinary
terms can't you just do a nearOrdered("X", "_ENDMARKER_") query? I don't see where you need
to subclass here. can you elaborate?

bq. 4) I found a bug in the iterators() method of DisjunctionSumScorer
great, can you submit the testcase?

bq. 3) MultiTermQueries don't return iterators unless you set their rewrite policies to something
other than CONSTANT_SCORE_REWRITE.
yeah the problem here is that we use a filter instead of a scorer, you should see an exception
right? I think it would make sense to have a MTQ rewrite a query on a ConstantScoreQuery instead
of a filter - we can't get a interval iter from a filter :/

I think overall we should move out of this issue and create separate issues for all you cases.
Also for the things robert mentioned like exploring "Scorere extends DocsAndPosEnum"
                
> 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: Simon Willnauer
>              Labels: gsoc2011, gsoc2012, lucene-gsoc-11, lucene-gsoc-12, mentor
>             Fix For: Positions Branch
>
>         Attachments: LUCENE-2878-OR.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, LUCENE-2878-vs-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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