SOLR-13681: make Lucene's index sorting directly configurable in Solr

solr/core/src/java/org/apache/solr/update/SolrIndexConfig.java

@@ -43,6 +43,8 @@
 import org.apache.solr.index.MergePolicyFactoryArgs;
 import org.apache.solr.index.SortingMergePolicy;
 import org.apache.solr.schema.IndexSchema;
+import org.apache.solr.search.SortSpec;
+import org.apache.solr.search.SortSpecParsing;
 import org.apache.solr.util.SolrPluginUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -83,6 +85,7 @@ public class SolrIndexConfig implements MapSerializable {
 
   public final int writeLockTimeout;
   public final String lockType;
+  public final String indexSort;
   public final PluginInfo mergePolicyFactoryInfo;
   public final PluginInfo mergeSchedulerInfo;
   public final PluginInfo metricsInfo;
@@ -102,6 +105,7 @@ private SolrIndexConfig(SolrConfig solrConfig) {
     maxCommitMergeWaitMillis = -1;
     writeLockTimeout = -1;
     lockType = DirectoryFactory.LOCK_TYPE_NATIVE;
+    indexSort = null;
     mergePolicyFactoryInfo = null;
     mergeSchedulerInfo = null;
     mergedSegmentWarmerInfo = null;
@@ -151,6 +155,7 @@ public SolrIndexConfig(SolrConfig solrConfig, String prefix, SolrIndexConfig def
 
     writeLockTimeout=solrConfig.getInt(prefix+"/writeLockTimeout", def.writeLockTimeout);
     lockType=solrConfig.get(prefix+"/lockType", def.lockType);
+    indexSort=solrConfig.get(prefix+"/indexSort", def.indexSort);
 
     List<PluginInfo> infos = solrConfig.readPluginInfos(prefix + "/metrics", false, false);
     if (infos.isEmpty()) {
@@ -209,6 +214,9 @@ public Map<String, Object> toMap(Map<String, Object> map) {
     if (metricsInfo != null) {
       map.put("metrics", metricsInfo);
     }
+    if (indexSort != null) {
+      map.put("indexSort", indexSort);
+    }
     if (mergePolicyFactoryInfo != null) {
       map.put("mergePolicyFactory", mergePolicyFactoryInfo);
     }
@@ -261,9 +269,19 @@ public IndexWriterConfig toIndexWriterConfig(SolrCore core) throws IOException {
     iwc.setMergeScheduler(mergeScheduler);
     iwc.setInfoStream(infoStream);
 
+    if (indexSort != null) {
+      SortSpec indexSortSpec = SortSpecParsing.parseSortSpec(indexSort, schema);
+      iwc.setIndexSort(indexSortSpec.getSort());
+    }
+
     if (mergePolicy instanceof SortingMergePolicy) {
-      Sort indexSort = ((SortingMergePolicy) mergePolicy).getSort();
-      iwc.setIndexSort(indexSort);
+      Sort mergeSort = ((SortingMergePolicy) mergePolicy).getSort();
+      Sort indexSort = iwc.getIndexSort();
+      if (indexSort != null && !indexSort.equals(mergeSort)) {
+        log.warn("indexSort={} differs from mergePolicySort={} (using indexSort)", indexSort, mergeSort);
+      } else {
+        iwc.setIndexSort(mergeSort);
+      }
     }
 
     iwc.setUseCompoundFile(useCompoundFile);

solr/core/src/test-files/solr/collection1/conf/solrconfig-sortingmergepolicyfactory.xml

@@ -29,6 +29,7 @@
       <str name="sort">timestamp_i_dvo desc</str>
     </mergePolicyFactory>
     <lockType>${solr.tests.lockType:single}</lockType>
+    <indexSort>timestamp_i_dvo desc</indexSort>
   </indexConfig>
 
   <requestHandler name="/select" class="solr.SearchHandler" />

solr/core/src/test/org/apache/solr/cloud/SolrIndexConfigIndexSortTest.java

@@ -0,0 +1,52 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.solr.cloud;
+
+import org.apache.solr.client.solrj.request.CollectionAdminRequest;
+import org.junit.Before;
+import org.junit.Test;
+
+public class SolrIndexConfigIndexSortTest extends SolrCloudTestCase {
+
+  private static String COLLECTION;
+
+  @Before
+  public void setUp() throws Exception {
+    super.setUp();
+
+    // decide collection name ...
+    COLLECTION = "collection"+(1+random().nextInt(100)) ;
+
+    // create and configure cluster
+    configureCluster(1)
+        .addConfig("conf", configset("cloud-minimal"))
+        .configure();
+
+    // create an empty collection
+    CollectionAdminRequest
+    .createCollection(COLLECTION, "conf", 1, 1)
+    .processAndWait(cluster.getSolrClient(), DEFAULT_TIMEOUT);
+    cluster.waitForActiveCollection(COLLECTION, 1, 1);
+  }
+
+  @Test
+  public void testStuff() throws Exception {
+    // TODO
+  }
+
+}

solr/core/src/test/org/apache/solr/update/SolrIndexConfigTest.java

@@ -146,6 +146,7 @@ public void testSortingMPSolrIndexConfigCreation() throws Exception {
     final Sort expected = new Sort(new SortField(expectedFieldName, expectedFieldType, expectedFieldSortDescending));
     final Sort actual = sortingMergePolicy.getSort();
     assertEquals("SortingMergePolicy.getSort", expected, actual);
+    assertEquals("indexSort", expected, iwc.getIndexSort());
   }
 
   public void testMergedSegmentWarmerIndexConfigCreation() throws Exception {