当我尝试在solr中使用carrot2聚类并基于字段进行分组时，我得到一个空指针异常。但是，群集查询在没有字段分组的情况下工作正常。 例如： 以下查询工作正常：
/clustering?q=text:apple&rows=500&carrot.title=title
但是，此查询会引发错误： /聚类？
q=text:tiger&rows=500&carrot.title=title&group=true&group.field=id&group.main=true
我想知道群集是否支持字段折叠或我做错了什么？ 错误的堆栈跟踪如下：
java.lang.NullPointerException
at org.apache.solr.handler.clustering.ClusteringComponent.process(ClusteringComponent.java:161)
at org.apache.solr.handler.component.SearchHandler.handleRequestBody(SearchHandler.java:208)
at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:135)
at org.apache.solr.core.RequestHandlers$LazyRequestHandlerWrapper.handleRequest(RequestHandlers.java:241)
at org.apache.solr.core.SolrCore.execute(SolrCore.java:1859)
at org.apache.solr.servlet.SolrDispatchFilter.execute(SolrDispatchFilter.java:703)
at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:406)
at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:195)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1419)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:455)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:557)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1075)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:384)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1009)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:255)
at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:154)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
at org.eclipse.jetty.server.Server.handle(Server.java:368)
at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:489)
at org.eclipse.jetty.server.BlockingHttpConnection.handleRequest(BlockingHttpConnection.java:53)
at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:942)
at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:1004)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:640)
at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)
at org.eclipse.jetty.server.BlockingHttpConnection.handle(BlockingHttpConnection.java:72)
at org.eclipse.jetty.server.bio.SocketConnector$ConnectorEndPoint.run(SocketConnector.java:264)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
at java.lang.Thread.run(Thread.java:724)