Revert "Rescore collapsed documents (#28521)"

This reverts commit f057fc2.
The rescorer does not resort the collapsed values inside the top docs
during rescoring. For this reason the Lucene rescorer is not compatible
with collapsing.
Relates #27243

Author: jimczi

rest-api-spec/src/main/resources/rest-api-spec/test/search/110_field_collapsing.yml

@@ -237,6 +237,28 @@ setup:
           search_after: [6]
           sort: [{ sort: desc }]
 
+---
+"field collapsing and rescore":
+
+  - skip:
+      version: " - 5.2.99"
+      reason:  this uses a new API that has been added in 5.3
+
+  - do:
+      catch:      /cannot use \`collapse\` in conjunction with \`rescore\`/
+      search:
+        index: test
+        type:  test
+        body:
+          collapse: { field: numeric_group }
+          rescore:
+            window_size: 20
+            query:
+              rescore_query:
+                match_all: {}
+              query_weight: 1
+              rescore_query_weight: 2
+
 ---
 "no hits and inner_hits":
 

server/src/main/java/org/elasticsearch/search/collapse/CollapseBuilder.java

@@ -225,6 +225,9 @@ public CollapseContext build(SearchContext context) {
         if (context.searchAfter() != null) {
             throw new SearchContextException(context, "cannot use `collapse` in conjunction with `search_after`");
         }
+        if (context.rescore() != null && context.rescore().isEmpty() == false) {
+            throw new SearchContextException(context, "cannot use `collapse` in conjunction with `rescore`");
+        }
 
         MappedFieldType fieldType = context.getQueryShardContext().fieldMapper(field);
         if (fieldType == null) {

server/src/main/java/org/elasticsearch/search/query/TopDocsCollectorContext.java

@@ -128,7 +128,6 @@ void postProcess(QuerySearchResult result) {
     static class CollapsingTopDocsCollectorContext extends TopDocsCollectorContext {
         private final DocValueFormat[] sortFmt;
         private final CollapsingTopDocsCollector<?> topDocsCollector;
-        private final boolean rescore;
 
         /**
          * Ctr
@@ -140,14 +139,13 @@ static class CollapsingTopDocsCollectorContext extends TopDocsCollectorContext {
         private CollapsingTopDocsCollectorContext(CollapseContext collapseContext,
                                                   @Nullable SortAndFormats sortAndFormats,
                                                   int numHits,
-                                                  boolean trackMaxScore, boolean rescore) {
+                                                  boolean trackMaxScore) {
             super(REASON_SEARCH_TOP_HITS, numHits);
             assert numHits > 0;
             assert collapseContext != null;
             Sort sort = sortAndFormats == null ? Sort.RELEVANCE : sortAndFormats.sort;
             this.sortFmt = sortAndFormats == null ? new DocValueFormat[] { DocValueFormat.RAW } : sortAndFormats.formats;
             this.topDocsCollector = collapseContext.createTopDocs(sort, numHits, trackMaxScore);
-            this.rescore = rescore;
         }
 
         @Override
@@ -160,11 +158,6 @@ Collector create(Collector in) throws IOException {
         void postProcess(QuerySearchResult result) throws IOException {
             result.topDocs(topDocsCollector.getTopDocs(), sortFmt);
         }
-
-        @Override
-        boolean shouldRescore() {
-            return rescore;
-        }
     }
 
     abstract static class SimpleTopDocsCollectorContext extends TopDocsCollectorContext {
@@ -339,6 +332,11 @@ static TopDocsCollectorContext createTopDocsCollectorContext(SearchContext searc
             return new ScrollingTopDocsCollectorContext(reader, query, searchContext.scrollContext(),
                 searchContext.sort(), numDocs, searchContext.trackScores(), searchContext.numberOfShards(),
                 searchContext.trackTotalHits(), hasFilterCollector);
+        } else if (searchContext.collapse() != null) {
+            boolean trackScores = searchContext.sort() == null ? true : searchContext.trackScores();
+            int numDocs = Math.min(searchContext.from() + searchContext.size(), totalNumDocs);
+            return new CollapsingTopDocsCollectorContext(searchContext.collapse(),
+                searchContext.sort(), numDocs, trackScores);
         } else {
             int numDocs = Math.min(searchContext.from() + searchContext.size(), totalNumDocs);
             final boolean rescore = searchContext.rescore().isEmpty() == false;
@@ -348,11 +346,6 @@ static TopDocsCollectorContext createTopDocsCollectorContext(SearchContext searc
                     numDocs = Math.max(numDocs, rescoreContext.getWindowSize());
                 }
             }
-            if (searchContext.collapse() != null) {
-                boolean trackScores = searchContext.sort() == null ? true : searchContext.trackScores();
-                return new CollapsingTopDocsCollectorContext(searchContext.collapse(),
-                    searchContext.sort(), numDocs, trackScores, rescore);
-            }
             return new SimpleTopDocsCollectorContext(reader, query, searchContext.sort(), searchContext.searchAfter(), numDocs,
                                                      searchContext.trackScores(), searchContext.trackTotalHits(), hasFilterCollector) {
                 @Override

server/src/test/java/org/elasticsearch/search/functionscore/QueryRescorerIT.java

@@ -36,17 +36,13 @@
 import org.elasticsearch.index.query.functionscore.ScoreFunctionBuilders;
 import org.elasticsearch.search.SearchHit;
 import org.elasticsearch.search.SearchHits;
-import org.elasticsearch.search.collapse.CollapseBuilder;
 import org.elasticsearch.search.rescore.QueryRescoreMode;
 import org.elasticsearch.search.rescore.QueryRescorerBuilder;
 import org.elasticsearch.search.sort.SortBuilders;
 import org.elasticsearch.test.ESIntegTestCase;
 
-import java.io.IOException;
 import java.util.Arrays;
 import java.util.Comparator;
-import java.util.Map;
-import java.util.stream.Collectors;
 
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_REPLICAS;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_SHARDS;
@@ -71,7 +67,6 @@
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertThirdHit;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.hasId;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.hasScore;
-import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
@@ -753,65 +748,4 @@ public void testRescorePhaseWithInvalidSort() throws Exception {
             assertThat(hit.getScore(), equalTo(101f));
         }
     }
-
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/28932")
-    public void testRescoreAfterCollapse() throws Exception {
-        assertAcked(prepareCreate("test")
-            .addMapping(
-                "type1",
-                jsonBuilder()
-                    .startObject()
-                    .startObject("properties")
-                    .startObject("group")
-                    .field("type", "keyword")
-                    .endObject()
-                    .endObject()
-                    .endObject())
-        );
-
-        ensureGreen("test");
-
-        indexDocument(1, "miss", "a", 1, 10);
-        indexDocument(2, "name", "a", 2, 20);
-        indexDocument(3, "name", "b", 2, 30);
-        // should be highest on rescore, but filtered out during collapse
-        indexDocument(4, "name", "b", 1, 40);
-
-        refresh("test");
-
-        SearchResponse searchResponse = client().prepareSearch("test")
-            .setTypes("type1")
-            .setQuery(staticScoreQuery("static_score"))
-            .addRescorer(new QueryRescorerBuilder(staticScoreQuery("static_rescore")))
-            .setCollapse(new CollapseBuilder("group"))
-            .get();
-
-        assertThat(searchResponse.getHits().totalHits, equalTo(3L));
-        assertThat(searchResponse.getHits().getHits().length, equalTo(2));
-
-        Map<String, Float> collapsedHits = Arrays
-            .stream(searchResponse.getHits().getHits())
-            .collect(Collectors.toMap(SearchHit::getId, SearchHit::getScore));
-
-        assertThat(collapsedHits.keySet(), containsInAnyOrder("2", "3"));
-        assertThat(collapsedHits.get("2"), equalTo(22F));
-        assertThat(collapsedHits.get("3"), equalTo(32F));
-    }
-
-    private QueryBuilder staticScoreQuery(String scoreField) {
-        return functionScoreQuery(termQuery("name", "name"), ScoreFunctionBuilders.fieldValueFactorFunction(scoreField))
-            .boostMode(CombineFunction.REPLACE);
-    }
-
-    private void indexDocument(int id, String name, String group, int score, int rescore) throws IOException {
-        XContentBuilder docBuilder =jsonBuilder()
-            .startObject()
-            .field("name", name)
-            .field("group", group)
-            .field("static_score", score)
-            .field("static_rescore", rescore)
-            .endObject();
-
-        client().prepareIndex("test", "type1", Integer.toString(id)).setSource(docBuilder).get();
-    }
 }