Add copy constructor to SearchRequest

For cross cluster search execution mode (see elastic#32125), we will need to take a search request that spans across multiple clusters (based on index prefixes e.g. cluster1:index, cluster2:index etc.) and split it into multiple search requests to be sent to each cluster. A copy constructor added to SearchRequest would make that easy and well maintanable in the future.

Something along the same lines already happens in `BulkByScrollParallelizationHelper`, but the corresponding code went outdated as some new fields were added to `SearchRequest` which were not added to the bulk by scroll code. A copy constructor helps making the task of copying a search request maintainable over time.

modules/reindex/src/main/java/org/elasticsearch/index/reindex/BulkByScrollParallelizationHelper.java

@@ -154,19 +154,9 @@ static SearchRequest[] sliceIntoSubRequests(SearchRequest request, String field,
                 }
                 slicedSource = request.source().copyWithNewSlice(sliceBuilder);
             }
-            slices[slice] = new SearchRequest()
-                    .source(slicedSource)
-                    .searchType(request.searchType())
-                    .indices(request.indices())
-                    .types(request.types())
-                    .routing(request.routing())
-                    .preference(request.preference())
-                    .requestCache(request.requestCache())
-                    .scroll(request.scroll())
-                    .indicesOptions(request.indicesOptions());
-            if (request.allowPartialSearchResults() != null) {
-                slices[slice].allowPartialSearchResults(request.allowPartialSearchResults());
-            }
+            SearchRequest searchRequest = new SearchRequest(request);
+            searchRequest.source(slicedSource);
+            slices[slice] = searchRequest;
         }
         return slices;
     }

server/src/main/java/org/elasticsearch/action/search/SearchRequest.java

@@ -77,7 +77,6 @@ public final class SearchRequest extends ActionRequest implements IndicesRequest
 
     private Boolean allowPartialSearchResults;
 
-
     private Scroll scroll;
 
     private int batchedReduceSize = DEFAULT_BATCHED_REDUCE_SIZE;
@@ -95,6 +94,25 @@ public final class SearchRequest extends ActionRequest implements IndicesRequest
     public SearchRequest() {
     }
 
+    /**
+     * Constructs a new search request from the provided search request
+     */
+    public SearchRequest(SearchRequest searchRequest) {
+        this.allowPartialSearchResults = searchRequest.allowPartialSearchResults;
+        this.batchedReduceSize = searchRequest.batchedReduceSize;
+        this.indices = searchRequest.indices;
+        this.indicesOptions = searchRequest.indicesOptions;
+        this.maxConcurrentShardRequests = searchRequest.maxConcurrentShardRequests;
+        this.preference = searchRequest.preference;
+        this.preFilterShardSize = searchRequest.preFilterShardSize;
+        this.requestCache = searchRequest.requestCache;
+        this.routing = searchRequest.routing;
+        this.scroll = searchRequest.scroll;
+        this.searchType = searchRequest.searchType;
+        this.source = searchRequest.source;
+        this.types = searchRequest.types;
+    }
+
     /**
      * Constructs a new search request against the indices. No indices provided here means that search
      * will run against all indices.

server/src/test/java/org/elasticsearch/search/SearchRequestTests.java

@@ -23,9 +23,6 @@
 import org.elasticsearch.action.search.SearchRequest;
 import org.elasticsearch.action.search.SearchType;
 import org.elasticsearch.action.support.IndicesOptions;
-import org.elasticsearch.common.io.stream.BytesStreamOutput;
-import org.elasticsearch.common.io.stream.NamedWriteableAwareStreamInput;
-import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.util.ArrayUtils;
 import org.elasticsearch.index.query.QueryBuilders;
@@ -42,15 +39,10 @@ public class SearchRequestTests extends AbstractSearchTestCase {
 
     public void testSerialization() throws Exception {
         SearchRequest searchRequest = createSearchRequest();
-        try (BytesStreamOutput output = new BytesStreamOutput()) {
-            searchRequest.writeTo(output);
-            try (StreamInput in = new NamedWriteableAwareStreamInput(output.bytes().streamInput(), namedWriteableRegistry)) {
-                SearchRequest deserializedRequest = new SearchRequest(in);
-                assertEquals(deserializedRequest, searchRequest);
-                assertEquals(deserializedRequest.hashCode(), searchRequest.hashCode());
-                assertNotSame(deserializedRequest, searchRequest);
-            }
-        }
+        SearchRequest deserializedRequest = copyWriteable(searchRequest, namedWriteableRegistry, SearchRequest::new);
+        assertEquals(deserializedRequest, searchRequest);
+        assertEquals(deserializedRequest.hashCode(), searchRequest.hashCode());
+        assertNotSame(deserializedRequest, searchRequest);
     }
 
     public void testIllegalArguments() {
@@ -142,7 +134,7 @@ public void testEqualsAndHashcode() throws IOException {
         checkEqualsAndHashCode(createSearchRequest(), SearchRequestTests::copyRequest, this::mutate);
     }
 
-    private SearchRequest mutate(SearchRequest searchRequest) throws IOException {
+    private SearchRequest mutate(SearchRequest searchRequest) {
         SearchRequest mutation = copyRequest(searchRequest);
         List<Runnable> mutators = new ArrayList<>();
         mutators.add(() -> mutation.indices(ArrayUtils.concat(searchRequest.indices(), new String[] { randomAlphaOfLength(10) })));
@@ -161,20 +153,7 @@ private SearchRequest mutate(SearchRequest searchRequest) throws IOException {
         return mutation;
     }
 
-    private static SearchRequest copyRequest(SearchRequest searchRequest) throws IOException {
-        SearchRequest result = new SearchRequest();
-        result.indices(searchRequest.indices());
-        result.indicesOptions(searchRequest.indicesOptions());
-        result.types(searchRequest.types());
-        result.searchType(searchRequest.searchType());
-        result.preference(searchRequest.preference());
-        result.routing(searchRequest.routing());
-        result.requestCache(searchRequest.requestCache());
-        result.allowPartialSearchResults(searchRequest.allowPartialSearchResults());
-        result.scroll(searchRequest.scroll());
-        if (searchRequest.source() != null) {
-            result.source(searchRequest.source());
-        }
-        return result;
+    private static SearchRequest copyRequest(SearchRequest searchRequest) {
+        return new SearchRequest(searchRequest);
     }
 }