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) <j...@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-unsubscr...@lucene.apache.org > For additional commands, e-mail: dev-h...@lucene.apache.org > >
