It may be a somewhat obscure pathway to produce this -- I only came
across it when, in applying faceting, I was using getDocListAndSet to
return both the DocList for output and the DocSet for facet
calculations, without fetching documents in any other way. Scores are
set to null here -- but, as you indicate, they are also set to null if
you getDocListNC, but that does not end up with an error. I agree
that the underlying issue should also be addressed, as well, but I
have not dug deeply enough into the internals to see the cause yet.
Here is the stack trace, when using a getDocListAndSet method without flags:
09> Started [EMAIL PROTECTED]
Jul 25, 2006 9:32:22 PM org.apache.solr.core.SolrCore execute
INFO: rows=10&explainOther=&start=0&indent=on&q=dell&fl=&qt=dismax&stylesheet=&v
ersion=2.1 0 140
Jul 25, 2006 9:32:22 PM org.apache.solr.core.SolrException log
SEVERE: java.lang.NullPointerException
at org.apache.solr.search.DocSlice$1.score(DocSlice.java:116)
at org.apache.solr.request.XMLWriter.writeDocList(XMLWriter.java:346)
at org.apache.solr.request.XMLWriter.writeVal(XMLWriter.java:385)
at org.apache.solr.request.XMLWriter.writeResponse(XMLWriter.java:106)
at org.apache.solr.request.XMLResponseWriter.write(XMLResponseWriter.jav
a:29)
at org.apache.solr.servlet.SolrServlet.doGet(SolrServlet.java:96)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:596)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:428
)
at org.mortbay.jetty.servlet.WebApplicationHandler.dispatch(WebApplicati
onHandler.java:473)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:5
68)
at org.mortbay.http.HttpContext.handle(HttpContext.java:1530)
at org.mortbay.jetty.servlet.WebApplicationContext.handle(WebApplication
Context.java:633)
at org.mortbay.http.HttpContext.handle(HttpContext.java:1482)
at org.mortbay.http.HttpServer.service(HttpServer.java:909)
at org.mortbay.http.HttpConnection.service(HttpConnection.java:820)
at org.mortbay.http.HttpConnection.handleNext(HttpConnection.java:986)
at org.mortbay.http.HttpConnection.handle(HttpConnection.java:837)
at org.mortbay.http.SocketListener.handleConnection(SocketListener.java:
245)
at org.mortbay.util.ThreadedServer.handle(ThreadedServer.java:357)
at org.mortbay.util.ThreadPool$PoolThread.run(ThreadPool.java:534)
Thanks,
Greg
On 7/25/06, Chris Hostetter <[EMAIL PROTECTED]> wrote:
: Thanks Greg, I just committed this.
I'm all in favor of the patch as commited, but the NPE still concerens me
... the OutputWriter should be able to cleanly deal with a DocList that
doesn't contain scores right?
Should we open a seperate issue to look into this? ... it seems like it
must be a somewhat obscure code path since I've certainly used Solr
without scores in the past.
Greg: do you by any chance have a stacktrace so we can see exactly where
the NPE was getting thrown from?
Yonik: do you have any idea what code path might cause an NPE?
:
: > Searcher's getDocListAndSet methods do not accept flags, can cause NPE when
writing output
: >
------------------------------------------------------------------------------------------
: >
: > Key: SOLR-39
: > URL: http://issues.apache.org/jira/browse/SOLR-39
: > Project: Solr
: > Issue Type: Bug
: > Components: search
: > Reporter: Greg Ludington
: > Assigned To: Yonik Seeley
: > Priority: Minor
: > Attachments: SolrIndexSearcherdocListAndSet.patch
: >
: >
: > SolrIndexSearcher's getDocListAndSet methods do not accept flags, which
can, in some cases, cause a Null Pointer Exception to be thrown when writing the
docListAndSet.docList as output. I came across the issue as I was implementing
faceting, see
http://www.nabble.com/Faceted-Browsing-Question-Discussion-tf1968854.html for the
discussion.
: > The simplest way to reproduce this is to modify DisMaxRequestHandler, by
changing this:
: > DocList results = s.getDocList(query, restrictions,
: > SolrPluginUtils.getSort(req),
: > req.getStart(), req.getLimit(),
: > flags);
: > rsp.add("search-results",results);
: > to
: > DocListAndSet listAndSet= s.getDocListAndSet(query, restrictions,
: > SolrPluginUtils.getSort(req),
: > req.getStart(), req.getLimit());
: > DocList results = listAndSet.docList;
: > rsp.add("search-results",results);
: > The root cause appears to be that the scores[] is set to null, so then the
DocIterator and its score() method is called, return scores[pos-1] will give null.
When getDocListAndSet(..) is invoked, it eventually can get down to this private
method:
: > private DocSet getDocListAndSetNC(DocListAndSet out, Query query, DocSet
filter, Sort lsort, int offset, int len, int flags) throws IOException
: > In that method, scores is assigned as follows:
: > scores = (flags&GET_SCORES)!=0 ? new float[nDocsReturned] : null;
: > Since getDocListAndSet() does not pass flags (except for the implicit
GET_DOCSET), scores is assigned as null, which eventually leads to the
NullPointerException if you try to output the docList . The attached patch does
not change the underlying mechanism of how scores is assigned, but works around
the issue by adding overloaded getDocListAndSet() methods that take an additional
flags parameter. After applying this patch, you can change the relevant bit in
DisMaxRequestHandler to:
: > DocListAndSet listAndSet= s.getDocListAndSet(query, restrictions,
: > SolrPluginUtils.getSort(req),
: > req.getStart(), req.getLimit(), flags);
: > DocList results = listAndSet.docList;
: > rsp.add("search-results",results);
: > and you will no longer see the NullPointerException
:
: --
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:
-Hoss
