#747 - @History findVersionsBetween query with Oracle has incorrect ordering

src/main/java/com/avaje/ebeaninternal/server/query/CQueryEngine.java

@@ -19,6 +19,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.sql.SQLException;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -204,15 +205,16 @@ public class CQueryEngine {
 
     SpiQuery<T> query = request.getQuery();
 
+    String sysPeriodLower = getSysPeriodLower(query);
     if (query.isVersionsBetween() && !historySupport.isBindAtFromClause()) {
       // just add as normal predicates using the lower bound
-      query.where().gt(getSysPeriodLower(query), query.getVersionStart());
-      query.where().lt(getSysPeriodLower(query), query.getVersionEnd());
+      query.where().gt(sysPeriodLower, query.getVersionStart());
+      query.where().lt(sysPeriodLower, query.getVersionEnd());
     }
 
     // order by id asc, lower sys period desc
     query.orderBy().asc(request.getBeanDescriptor().getIdProperty().getName());
-    query.orderBy().desc(getSysPeriodLower(query));
+    query.orderBy().desc(sysPeriodLower);
 
     CQuery<T> cquery = queryBuilder.buildQuery(request);
     try {
@@ -222,6 +224,9 @@ public class CQueryEngine {
       }
 
       List<Version<T>> versions = cquery.readVersions();
+      // just order in memory rather than use NULLS LAST as that
+      // is not universally supported, not expect huge list here
+      Collections.sort(versions, OrderVersionDesc.INSTANCE);
       deriveVersionDiffs(versions, request);
 
       if (request.isLogSummary()) {

src/main/java/com/avaje/ebeaninternal/server/query/OrderVersionDesc.java

@@ -0,0 +1,29 @@
+package com.avaje.ebeaninternal.server.query;
+
+import com.avaje.ebean.Version;
+
+import java.sql.Timestamp;
+import java.util.Comparator;
+
+/**
+ * Compare Version beans in descending order with nulls last.
+ */
+class OrderVersionDesc implements Comparator<Version<?>> {
+
+  static final OrderVersionDesc INSTANCE = new OrderVersionDesc();
+
+  @Override
+  public int compare(Version<?> o1, Version<?> o2) {
+
+    Timestamp v1 = o1.getStart();
+    if (v1 == null) {
+      return 1;
+    }
+    Timestamp v2 = o2.getStart();
+    if (v2 == null) {
+      return -1;
+    }
+    return v1.compareTo(v2) * -1;
+  }
+
+}