[
https://issues.apache.org/jira/browse/LUCENE-2458?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12870353#action_12870353
]
Shai Erera commented on LUCENE-2458:
------------------------------------
FWIW, I agree w/ Mark. I don't think it's a bug, but more of a user option.
Whether it should be specified by a setter, or an extension of QP - I have no
strong feelings for either of them, so either would be fine by me.
And for what's it's also worth, we've once worked w/ a Japanese linguist, who
suggested that we always convert queries like [abcd] to [abcd "abcd"] or just
["abcd"] because if someone had already bothered to write them like that, then
phrase matching should contribute to the rank of the documents. IMO, if someone
had gone even further by writing [field:abcd], then even if the query should be
[field:a field:b field:c field:d], executing the query [field:"abcd"] is still
important and better.
So .. I'm not trying to argue what should be the default behavior, because that
is subject to personal flavor and apps requirements -- only to emphasize that
there are many user cases out there, and we should cater for such scenarios.
The extension way is already supported, right? So perhaps we just need to
document the current behavior, and not change anything? Or, introduce a setter,
that will do the simple thing - either keep it as a phrase or break it down to
terms. More sophisticated scenarios can be dealt through extension.
> 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-unsubscr...@lucene.apache.org
For additional commands, e-mail: dev-h...@lucene.apache.org
