Revert "Rescore collapsed documents (elastic#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 elastic#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();
-    }
 }