GH-2501 - Use more performant operations to store mapped records.

Author: meistermeier

src/main/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jEntityConverter.java

@@ -755,7 +755,8 @@ static class KnownObjects {
 		private final Lock write = lock.writeLock();
 
 		private final Map<Long, Object> internalIdStore = new HashMap<>();
-		private final Map<Long, Boolean> internalNextRecord = new HashMap<>();
+		private final Map<Long, Boolean> internalCurrentRecord = new HashMap<>();
+		private final Set<Long> previousRecords = new HashSet<>();
 		private final Set<Long> idsInCreation = new HashSet<>();
 
 		private void storeObject(@Nullable Long internalId, Object object) {
@@ -766,7 +767,7 @@ private void storeObject(@Nullable Long internalId, Object object) {
 				write.lock();
 				idsInCreation.remove(internalId);
 				internalIdStore.put(internalId, object);
-				internalNextRecord.put(internalId, false);
+				internalCurrentRecord.put(internalId, false);
 			} finally {
 				write.unlock();
 			}
@@ -837,23 +838,19 @@ private boolean alreadyMappedInPreviousRecord(@Nullable Long internalId) {
 
 				read.lock();
 
-				Boolean nextRecord = internalNextRecord.get(internalId);
-
-				if (nextRecord != null) {
-					return nextRecord;
-				}
+				return previousRecords.contains(internalId) || internalCurrentRecord.get(internalId);
 
 			} finally {
 				read.unlock();
 			}
-			return false;
 		}
 
 		/**
 		 * Mark all currently existing objects as mapped.
 		 */
 		private void nextRecord() {
-			internalNextRecord.replaceAll((x, y) -> true);
+			previousRecords.addAll(internalCurrentRecord.keySet());
+			internalCurrentRecord.clear();
 		}
 	}
 }