LUCENE-6309: disable coord when scores are not needed, or the scoring fn does not use it

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1662964 13f79535-47bb-0310-9956-ffa450edef68

lucene/core/src/java/org/apache/lucene/search/BooleanWeight.java

@@ -42,13 +42,13 @@ public class BooleanWeight extends Weight {
   protected int maxCoord;  // num optional + num required
   private final boolean disableCoord;
   private final boolean needsScores;
+  private final float coords[];
 
   public BooleanWeight(BooleanQuery query, IndexSearcher searcher, boolean needsScores, boolean disableCoord) throws IOException {
     super(query);
     this.query = query;
     this.needsScores = needsScores;
     this.similarity = searcher.getSimilarity();
-    this.disableCoord = disableCoord;
     weights = new ArrayList<>(query.clauses().size());
     for (int i = 0 ; i < query.clauses().size(); i++) {
       BooleanClause c = query.clauses().get(i);
@@ -58,6 +58,23 @@ public class BooleanWeight extends Weight {
         maxCoord++;
       }
     }
+    
+    // precompute coords (0..N, N).
+    // set disableCoord when its explicit, scores are not needed, no scoring clauses, or the sim doesn't use it.
+    coords = new float[maxCoord+1];
+    Arrays.fill(coords, 1F);
+    coords[0] = 0f;
+    if (maxCoord > 0 && needsScores && disableCoord == false) {
+      // compute coords from the similarity, look for any actual ones.
+      boolean seenActualCoord = false;
+      for (int i = 1; i < coords.length; i++) {
+        coords[i] = coord(i, maxCoord);
+        seenActualCoord |= (coords[i] != 1F);
+      }
+      this.disableCoord = seenActualCoord == false;
+    } else {
+      this.disableCoord = true;
+    }
   }
 
   @Override
@@ -346,9 +363,9 @@ public class BooleanWeight extends Weight {
       }
     } else {
       if (minShouldMatch > 0) {
-        return new BooleanTopLevelScorers.CoordinatingConjunctionScorer(this, coords(), req, requiredScoring.size(), opt);
+        return new BooleanTopLevelScorers.CoordinatingConjunctionScorer(this, coords, req, requiredScoring.size(), opt);
       } else {
-        return new BooleanTopLevelScorers.ReqMultiOptScorer(req, opt, requiredScoring.size(), coords()); 
+        return new BooleanTopLevelScorers.ReqMultiOptScorer(req, opt, requiredScoring.size(), coords); 
       }
     }
   }
@@ -395,10 +412,11 @@ public class BooleanWeight extends Weight {
     } else {
       float coords[];
       if (disableCoord) {
+        // sneaky: when we do a mixed conjunction/disjunction, we need a fake for the disjunction part.
         coords = new float[optional.size()+1];
         Arrays.fill(coords, 1F);
       } else {
-        coords = coords();
+        coords = this.coords;
       }
       if (minShouldMatch > 1) {
         return new MinShouldMatchSumScorer(this, optional, minShouldMatch, coords);
@@ -407,13 +425,4 @@ public class BooleanWeight extends Weight {
       }
     }
   }
-  
-  private float[] coords() {
-    float[] coords = new float[maxCoord+1];
-    coords[0] = 0F;
-    for (int i = 1; i < coords.length; i++) {
-      coords[i] = coord(i, maxCoord);
-    }
-    return coords;
-  }
 }

lucene/core/src/test/org/apache/lucene/search/TestBooleanQuery.java

@@ -674,7 +674,7 @@ public class TestBooleanQuery extends LuceneTestCase {
 
     final Weight weight = searcher.createNormalizedWeight(q, random().nextBoolean());
     final Scorer scorer = weight.scorer(reader.leaves().get(0), null);
-    assertTrue(scorer instanceof BoostedScorer);
+    assertTrue(scorer instanceof BoostedScorer || scorer instanceof ExactPhraseScorer);
     assertNotNull(scorer.asTwoPhaseIterator());
 
     reader.close();