Faceting on a field in SolrCloud with docValues=true and indexed=false fails

最近在试着在SolrCloud中用docValues。不过在做某个docValues=true的数字域统计时，会报错。而在做String域的统计或者数字域的排序则没有问题。

我的int域型配置如下：

<fieldType name="int" class="solr.TrieIntField" precisionStep="0" positionIncrementGap="0"/>

域配置如下：

<field name="type" type="int" indexed="false" stored="false" multiValued="false" docValues="true" useDocValuesAsStored="true"/>

之后读到文档中的这段话，便在域的配置中添加了required="true".

Default numeric field types. For faster range queries, consider the
tint/tfloat/tlong/tdouble types. These fields support doc values, but
they require the field to be single-valued and either be required or
have a default value.

但是结果还是有错误：

null:org.apache.solr.common.SolrException: Exception during facet.field: company_type    at org.apache.solr.request.SimpleFacets$3.call(SimpleFacets.java:721)    at org.apache.solr.request.SimpleFacets$3.call(SimpleFacets.java:706)    at java.util.concurrent.FutureTask.run(FutureTask.java:266)    at org.apache.solr.request.SimpleFacets$2.execute(SimpleFacets.java:660)    at org.apache.solr.request.SimpleFacets.getFacetFieldCounts(SimpleFacets.java:731)    at org.apache.solr.handler.component.FacetComponent.getFacetCounts(FacetComponent.java:294)    at org.apache.solr.handler.component.FacetComponent.process(FacetComponent.java:256)    at org.apache.solr.handler.component.SearchHandler.handleRequestBody(SearchHandler.java:272)    at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:155)    at org.apache.solr.core.SolrCore.execute(SolrCore.java:2102)    at org.apache.solr.servlet.HttpSolrCall.execute(HttpSolrCall.java:654)    at org.apache.solr.servlet.HttpSolrCall.call(HttpSolrCall.java:460)    at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:257)    at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:208)    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:585)    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:577)    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:215)    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:110)    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)    at org.eclipse.jetty.server.Server.handle(Server.java:499)    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310)    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540)    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)    at java.lang.Thread.run(Thread.java:745)Caused by: java.lang.IllegalStateException: Cannot use facet.mincount=0 on field company_type which is not indexed    at org.apache.solr.request.NumericFacets.getCounts(NumericFacets.java:257)    at org.apache.solr.request.SimpleFacets.getTermCounts(SimpleFacets.java:454)    at org.apache.solr.request.SimpleFacets.getTermCounts(SimpleFacets.java:382)    at org.apache.solr.request.SimpleFacets$3.call(SimpleFacets.java:715)    ... 33 more

Google了一下，找到这个issue，SOLR-5260。 上面有个patch，修改了/solr/core/src/java/org/apache/solr/request/NumericFacets.java的代码：

       if (zeros && (limit < 0 || result.size() < limit)) { // need to merge with the term dict-        if (!sf.indexed()) {-          throw new IllegalStateException("Cannot use " + FacetParams.FACET_MINCOUNT + "=0 on field " + sf.getName() + " which is not indexed");+        if (!sf.indexed() && !sf.hasDocValues()) {+          throw new IllegalStateException("Cannot use " + FacetParams.FACET_MINCOUNT + "=0 on field " + sf.getName() + " which is neither indexed nor docValues");         }         // Add zeros until there are limit results         final Set<String> alreadySeen = new HashSet<>();

所以，先去http://www.apache.org/dyn/closer.lua/lucene/solr/5.5.4把solr-5.5.4-src.tgz下载并解压，导入Eclipse。点击File-Import-General-File System, 选择解压好的文件夹。

找到NumericFacets.java并修改代码。由于我这边把源代码导入后提示有错误，所以我把整个project导出jar包。

（这里注意Solr-5.5.4需要用java 1.7导出，我一开始使用了java 1.8，有个别Collection做facet的时候会报错：Error while processing facet fields: java.lang.UnsupportedClassVersionError，查了下这个错误是jdk版本号不对导致的）

然后用WinRAR打开jar包，复制NumericFacets相关的class，替换到原来Solr-5.5.4的solr-5.5.4\solr-5.5.4\server\solr-webapp\webapp\WEB-INF\lib\solr-core-5.5.4.jar中。

然后把修改过的solr-core-5.5.4放入服务器中对应的solr文件夹中/server/solr-webapp/webapp/WEB-INF/lib/solr-core-5.5.4。不用重新建索引，只需分别重启几个Solr节点，再测试docValues，可以使用facet。