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http://issues.apache.org/bugzilla/show_bug.cgi?id=31841 MultiSearcher problems with Similarity.docFreq() Summary: MultiSearcher problems with Similarity.docFreq() Product: Lucene Version: 1.4 Platform: All OS/Version: Other Status: NEW Severity: Normal Priority: Other Component: Search AssignedTo: [EMAIL PROTECTED] ReportedBy: [EMAIL PROTECTED] When MultiSearcher invokes its subsearchers, it is the subsearchers' docFreq() that is accessed by Similarity.docFreq(). This causes idf's to be computed local to each index rather than globally, which causes ranking across multiple indices to not be equivalent to ranking across the entire global collection. The attached files (if I can figure out how to attach them) provide a potential partial solution for this. They properly fix a simple test case, RankingTest, that was provided by Daniel Naber. The changes are: 1. Searcher: Add topmostSearcher() field with getter and setter to record the outermost Searcher. Default to this. 2. MultiSearcher: Pass down the topmostSearcher when creating the subsearchers. 3. IndexSearcher: Call Query.weight() everywhere with the topmostSearcher instead of this. 4. Query: Provide a default implementation of Query.combine() so that MultiSearcher works with all queries. Problems or possible problems I see: 1. This does not address the same issue with RemoteSearchable. RemoteSearchable is not a Searcher, nor can it be due to lack of multiple inheritance in Java, but Query.weight() requires a Searcher. Perhaps Query.weight() should be changed to take a Searchable, but this requires changing many places and I suspect would break apps. 2. There may be other places that topmostSearcher should be used instead of this. 3. The default implementation for Query.combine() is a guess on my part - it works for TermQuery. It's fragile in that the default implementation will hide bugs caused by queries that inadvertently omit a more precise Query.combine() method. 4. The prior comment on Query.combine() indicates that whoever wrote it was fully aware of this problem and so probably had another usage in mind, so the whole issue may just be Daniel's usage in the test case. It's not apparent to me, so I probably don't understand something. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
