SOLR-17319 : Combined Query Feature for Multi Query Execution

solr/core/src/java/org/apache/solr/handler/component/CombinedQueryResponseBuilder.java

@@ -0,0 +1,44 @@
+/*
+ * 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.handler.component;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.solr.request.SolrQueryRequest;
+import org.apache.solr.response.SolrQueryResponse;
+
+/**
+ * The CombinedQueryResponseBuilder class extends the ResponseBuilder class and is responsible for
+ * building a combined response for multiple SearchComponent objects. It orchestrates the process of
+ * constructing the SolrQueryResponse by aggregating results from various components.
+ */
+public class CombinedQueryResponseBuilder extends ResponseBuilder {
+
+  public final List<ResponseBuilder> responseBuilders = new ArrayList<>();
+
+  /**
+   * Constructs a CombinedQueryResponseBuilder instance.
+   *
+   * @param req the SolrQueryRequest object containing the query parameters and context.
+   * @param rsp the SolrQueryResponse object to which the combined results will be added.
+   * @param components a list of SearchComponent objects that will be used to build the response.
+   */
+  public CombinedQueryResponseBuilder(
+      SolrQueryRequest req, SolrQueryResponse rsp, List<SearchComponent> components) {
+    super(req, rsp, components);
+  }
+}

solr/core/src/java/org/apache/solr/handler/component/CombinedQuerySearchHandler.java

@@ -0,0 +1,75 @@
+/*
+ * 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.handler.component;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.solr.common.params.CombinerParams;
+import org.apache.solr.request.SolrQueryRequest;
+import org.apache.solr.response.SolrQueryResponse;
+import org.apache.solr.search.facet.FacetModule;
+
+/**
+ * The CombinedQuerySearchHandler class extends the SearchHandler and provides custom behavior for
+ * handling combined queries. It overrides methods to create a response builder based on the {@link
+ * CombinerParams#COMBINER} parameter and to define the default components included in the search
+ * configuration.
+ */
+public class CombinedQuerySearchHandler extends SearchHandler {
+
+  /**
+   * Overrides the default response builder creation method. This method checks if the {@link
+   * CombinerParams#COMBINER} parameter is set to true in the request. If it is, it returns an
+   * instance of {@link CombinedQueryResponseBuilder}, otherwise, it returns an instance of {@link
+   * ResponseBuilder}.
+   *
+   * @param req the SolrQueryRequest object
+   * @param rsp the SolrQueryResponse object
+   * @param components the list of SearchComponent objects
+   * @return the appropriate ResponseBuilder instance based on the CombinerParams.COMBINER parameter
+   */
+  @Override
+  protected ResponseBuilder newResponseBuilder(
+      SolrQueryRequest req, SolrQueryResponse rsp, List<SearchComponent> components) {
+    if (req.getParams().getBool(CombinerParams.COMBINER, false)) {
+      return new CombinedQueryResponseBuilder(req, rsp, components);
+    }
+    return new ResponseBuilder(req, rsp, components);
+  }
+
+  /**
+   * Overrides the default components and returns a list of component names that are included in the
+   * default configuration.
+   *
+   * @return a list of component names
+   */
+  @Override
+  @SuppressWarnings("unchecked")
+  protected List<String> getDefaultComponents() {
+    List<String> names = new ArrayList<>(9);
+    names.add(CombinedQueryComponent.COMPONENT_NAME);
+    names.add(FacetComponent.COMPONENT_NAME);
+    names.add(FacetModule.COMPONENT_NAME);
+    names.add(MoreLikeThisComponent.COMPONENT_NAME);
+    names.add(HighlightComponent.COMPONENT_NAME);
+    names.add(StatsComponent.COMPONENT_NAME);
+    names.add(DebugComponent.COMPONENT_NAME);
+    names.add(ExpandComponent.COMPONENT_NAME);
+    names.add(TermsComponent.COMPONENT_NAME);
+    return names;
+  }
+}

solr/core/src/java/org/apache/solr/search/combine/QueryAndResponseCombiner.java

@@ -0,0 +1,103 @@
+/*
+ * 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.search.combine;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+import org.apache.lucene.search.Explanation;
+import org.apache.lucene.search.Query;
+import org.apache.solr.common.SolrException;
+import org.apache.solr.common.params.CombinerParams;
+import org.apache.solr.common.params.SolrParams;
+import org.apache.solr.common.util.NamedList;
+import org.apache.solr.handler.component.ShardDoc;
+import org.apache.solr.schema.IndexSchema;
+import org.apache.solr.search.QueryResult;
+import org.apache.solr.search.SolrIndexSearcher;
+
+/**
+ * The QueryAndResponseCombiner class is an abstract base class for combining query results and
+ * shard documents. It provides a framework for different algorithms to be implemented for merging
+ * ranked lists and shard documents.
+ */
+public abstract class QueryAndResponseCombiner {
+
+  public abstract void init(NamedList<?> args);
+
+  /**
+   * Combines multiple ranked lists into a single QueryResult.
+   *
+   * @param rankedLists a list of ranked lists to be combined
+   * @param solrParams params to be used when provided at query time
+   * @return a new QueryResult containing the combined results
+   * @throws IllegalArgumentException if the input list is empty
+   */
+  public abstract QueryResult combine(List<QueryResult> rankedLists, SolrParams solrParams);
+
+  /**
+   * Combines shard documents based on the provided map.
+   *
+   * @param shardDocMap a map where keys represent shard IDs and values are lists of ShardDocs for
+   *     each shard
+   * @param solrParams params to be used when provided at query time
+   * @return a combined list of ShardDocs from all shards
+   */
+  public abstract List<ShardDoc> combine(
+      Map<String, List<ShardDoc>> shardDocMap, SolrParams solrParams);
+
+  /**
+   * Retrieves a list of explanations for the given queries and results.
+   *
+   * @param queryKeys the keys associated with the queries
+   * @param queries the list of queries for which explanations are requested
+   * @param queryResult the list of QueryResult corresponding to each query
+   * @param searcher the SolrIndexSearcher used to perform the search
+   * @param schema the IndexSchema used to interpret the search results
+   * @param solrParams params to be used when provided at query time
+   * @return a list of explanations for the given queries and results
+   * @throws IOException if an I/O error occurs during the explanation retrieval process
+   */
+  public abstract NamedList<Explanation> getExplanations(
+      String[] queryKeys,
+      List<Query> queries,
+      List<QueryResult> queryResult,
+      SolrIndexSearcher searcher,
+      IndexSchema schema,
+      SolrParams solrParams)
+      throws IOException;
+
+  /**
+   * Retrieves an implementation of the QueryAndResponseCombiner based on the specified algorithm.
+   *
+   * @param requestParams the SolrParams containing the request parameters, including the combiner
+   *     algorithm.
+   * @param combiners The already initialised map of QueryAndResponseCombiner
+   * @return an instance of QueryAndResponseCombiner corresponding to the specified algorithm.
+   * @throws SolrException if an unknown combiner algorithm is specified.
+   */
+  public static QueryAndResponseCombiner getImplementation(
+      SolrParams requestParams, Map<String, QueryAndResponseCombiner> combiners) {
+    String algorithm =
+        requestParams.get(CombinerParams.COMBINER_ALGORITHM, CombinerParams.DEFAULT_COMBINER);
+    if (combiners.containsKey(algorithm)) {
+      return combiners.get(algorithm);
+    }
+    throw new SolrException(
+        SolrException.ErrorCode.BAD_REQUEST, "Unknown Combining algorithm: " + algorithm);
+  }
+}