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From Shai Erera <ser...@gmail.com>
Subject Re: [jira] Commented: (LUCENE-2458) queryparser shouldn't generate phrasequeries based on term count
Date Sun, 23 May 2010 16:54:47 GMT
Sorry hit the send button too early

The QP should work like that:
(1) It parses the query, creating fragments
(2) It does some out-of-the-box handling of those fragments

People should be able to override that handling of fragments. But people
should not touch (1).

And so if we keep thinking of QP that way, then we'll have THE QP for (1),
because there can be only one, and a "we think this is best for most people"
handling of fragments (2). So for (1), QP would create the fragment field +
value, and it'll be your choice how to interpret that. QP will provide a
default handling for it (today's behavior is fine w/ me).

We already do this today in other, equally important places - IndexWriter.
It has all sorts of configs and have a "what we think is good for most"
defaults. People can override it, and that's it.

And I think I do understand the issue Robert, even though I speak less
languages then you are. It is all about tokenization. My QP does the parsing
I've mentioned - it breaks the query into fragments and then handles them.
There is a default behavior which people can override. And that behavior is
all about tokenization.

Shai

On Sun, May 23, 2010 at 7:47 PM, Shai Erera <serera@gmail.com> wrote:

> Robert - I hope hitting the keyboard hard makes you happy :)
>
> I do get the issue. And I still think that CJK queries are just a small
> percentage of all queries that are used in the world today. Or at least by
> Lucene. And I'm not sure why we want to change the default for ALL OTHER
> LANGUAGES, just so that CJK QUERIES will hAVe A diFFEreNT BeHAvioR
> !!?!?!?!?!?!??!?!?!
>
>
>
>
> On Sun, May 23, 2010 at 7:42 PM, Robert Muir <rcmuir@gmail.com> wrote:
>
>> These comments lead me to believe you don't understand the issue.
>>
>> Do you understand that *ALL* CJK queries are made into phrase queries,
>> regardless of tokenizer?!!?!?!
>>
>> On Sun, May 23, 2010 at 12:38 PM, Uwe Schindler <uwe@thetaphi.de> wrote:
>> > Same here, as already noted in the issue.
>> >
>> >
>> >
>> > Uwe
>> >
>> >
>> >
>> > -----
>> >
>> > Uwe Schindler
>> >
>> > H.-H.-Meier-Allee 63, D-28213 Bremen
>> >
>> > http://www.thetaphi.de
>> >
>> > eMail: uwe@thetaphi.de
>> >
>> >
>> >
>> > From: Shai Erera [mailto:serera@gmail.com]
>> > Sent: Sunday, May 23, 2010 6:34 PM
>> >
>> > To: dev@lucene.apache.org
>> > Subject: Re: [jira] Commented: (LUCENE-2458) queryparser shouldn't
>> generate
>> > phrasequeries based on term count
>> >
>> >
>> >
>> > Robert - is the effect on scoring also on English and other European
>> > languages? Or is it mostly for ngram-based languages, and especially
>> CJK?
>> >
>> > I want to stress that not all ngram-based languages are affected by this
>> > behavior, especially those for which we do ngram just because of a lack
>> of
>> > good tokenizer.
>> >
>> > That's why I'm not sure the default should be changed and I'm all for a
>> > getter/setter. If however it turns out the default MUST be changed, then
>> I
>> > support the Version + getter/setter approach.
>> >
>> > Shai
>> >
>> > On Sun, May 23, 2010 at 6:00 PM, Uwe Schindler (JIRA) <jira@apache.org>
>> > wrote:
>> >
>> >    [
>> >
>> https://issues.apache.org/jira/browse/LUCENE-2458?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12870410#action_12870410
>> > ]
>> >
>> > Uwe Schindler commented on LUCENE-2458:
>> > ---------------------------------------
>> >
>> > Hi Robert,
>> >
>> > I also agree with Mark (as you know). We can have both:
>> > - Version for a good default (3.1 will get the new non-phrase-query
>> > behavior)
>> > - A separate getsetter for this option
>> > (set/getCreatePhraseQueryOnConcenattedTerms or whatever)
>> >
>> > This would give you the best from both worlds.
>> >
>> >> queryparser shouldn't generate phrasequeries based on term count
>> >> ----------------------------------------------------------------
>> >>
>> >>                 Key: LUCENE-2458
>> >>                 URL: https://issues.apache.org/jira/browse/LUCENE-2458
>> >>             Project: Lucene - Java
>> >>          Issue Type: Bug
>> >>          Components: QueryParser
>> >>            Reporter: Robert Muir
>> >>            Assignee: Robert Muir
>> >>            Priority: Blocker
>> >>             Fix For: 3.1, 4.0
>> >>
>> >>         Attachments: LUCENE-2458.patch, LUCENE-2458.patch
>> >>
>> >>
>> >> The current method in the queryparser to generate phrasequeries is
>> wrong:
>> >> The Query Syntax documentation
>> >> (http://lucene.apache.org/java/3_0_1/queryparsersyntax.html) states:
>> >> {noformat}
>> >> A Phrase is a group of words surrounded by double quotes such as "hello
>> >> dolly".
>> >> {noformat}
>> >> But as we know, this isn't actually true.
>> >> Instead the terms are first divided on whitespace, then the analyzer
>> term
>> >> count is used as some sort of "heuristic" to determine if its a phrase
>> query
>> >> or not.
>> >> This assumption is a disaster for languages that don't use whitespace
>> >> separation: CJK, compounding European languages like German, Finnish,
>> etc.
>> >> It also
>> >> makes it difficult for people to use n-gram analysis techniques. In
>> these
>> >> cases you get bad relevance (MAP improves nearly *10x* if you use a
>> >> PositionFilter at query-time to "turn this off" for chinese).
>> >> For even english, this undocumented behavior is bad. Perhaps in some
>> cases
>> >> its being abused as some heuristic to "second guess" the tokenizer and
>> piece
>> >> back things it shouldn't have split, but for large collections, doing
>> things
>> >> like generating phrasequeries because StandardTokenizer split a
>> compound on
>> >> a dash can cause serious performance problems. Instead people should
>> analyze
>> >> their text with the appropriate methods, and QueryParser should only
>> >> generate phrase queries when the syntax asks for one.
>> >> The PositionFilter in contrib can be seen as a workaround, but its
>> pretty
>> >> obscure and people are not familiar with it. The result is we have bad
>> >> out-of-box behavior for many languages, and bad performance for others
>> on
>> >> some inputs.
>> >> I propose instead that we change the grammar to actually look for
>> double
>> >> quotes to determine when to generate a phrase query, consistent with
>> the
>> >> documentation.
>> >
>> > --
>> > This message is automatically generated by JIRA.
>> > -
>> > You can reply to this email to add a comment to the issue online.
>> >
>> >
>> > ---------------------------------------------------------------------
>> >
>> > To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org
>> >
>> > For additional commands, e-mail: dev-help@lucene.apache.org
>> >
>> >
>>
>>
>>
>> --
>> Robert Muir
>> rcmuir@gmail.com
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org
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>>
>>
>

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