profilePageCacheHitRatio should default to 0.

As a result, fix how `hasPageCacheStats` is computed too.

Author: Zhen Li

driver/src/main/java/org/neo4j/driver/internal/summary/InternalProfiledPlan.java

@@ -61,7 +61,7 @@ public long records()
     @Override
     public boolean hasPageCacheStats()
     {
-        return pageCacheHits > 0 || pageCacheMisses > 0 || !Double.isNaN( pageCacheHitRatio );
+        return pageCacheHits > 0 || pageCacheMisses > 0 || pageCacheHitRatio > 0;
     }
 
     @Override
@@ -96,7 +96,7 @@ public ProfiledPlan create( String operatorType, Map<String,Value> arguments, Li
         {
             return new InternalProfiledPlan( operatorType, arguments, identifiers, children, originalPlanValue.get( "dbHits" ).asLong( 0 ),
                     originalPlanValue.get( "rows" ).asLong( 0 ), originalPlanValue.get( "pageCacheHits" ).asLong( 0 ),
-                    originalPlanValue.get( "pageCacheMisses" ).asLong( 0 ), originalPlanValue.get( "pageCacheHitRatio" ).asDouble( Double.NaN ),
+                    originalPlanValue.get( "pageCacheMisses" ).asLong( 0 ), originalPlanValue.get( "pageCacheHitRatio" ).asDouble( 0 ),
                     originalPlanValue.get( "time" ).asLong( 0 ) );
         }
     };

driver/src/main/java/org/neo4j/driver/summary/ProfiledPlan.java

@@ -53,7 +53,7 @@ public interface ProfiledPlan extends Plan
     long pageCacheMisses();
 
     /**
-     * @return the ratio of page cache hits to total number of lookups or {@link Double#NaN} if no data is available
+     * @return the ratio of page cache hits to total number of lookups or 0 if no data is available
      */
     double pageCacheHitRatio();
 

driver/src/test/java/org/neo4j/driver/internal/util/MetadataExtractorTest.java

@@ -252,7 +252,7 @@ void shouldBuildResultSummaryWithProfiledPlan()
         assertEquals( 242424, summary.profile().dbHits() );
         assertEquals( 999, summary.profile().time() );
         assertFalse( summary.profile().hasPageCacheStats() );
-        assertEquals( Double.NaN, summary.profile().pageCacheHitRatio() );
+        assertEquals( 0, summary.profile().pageCacheHitRatio() );
         assertEquals( 0, summary.profile().pageCacheMisses() );
         assertEquals( 0, summary.profile().pageCacheHits() );