DB2:Unselect LOBs when making a distinct select

ebean-core/src/main/java/io/ebeaninternal/server/deploy/BeanProperty.java

@@ -1160,7 +1160,26 @@ public class BeanProperty implements ElPropertyValue, Property, STreeProperty {
   public boolean isLob() {
     return lob;
   }
-
+  
+  /**
+   * Returns true if this <code>isLob()</code> or the type will effectively map to a lob. 
+   */
+  public boolean isDbLob() {
+    if (lob) {
+      return true;
+    }
+    switch (dbType) {
+    case DbPlatformType.JSON:
+    case DbPlatformType.JSONB:
+      return dbLength == 0; // must be analog to DbPlatformTypeMapping.lookup
+    case DbPlatformType.JSONBlob:
+    case DbPlatformType.JSONClob:
+      return true;
+    default:
+      return false;
+    }
+  }
+  
   public static boolean isLobType(int type) {
     switch (type) {
       case Types.CLOB:

ebean-core/src/main/java/io/ebeaninternal/server/deploy/DynamicPropertyAggregationFormula.java

@@ -62,4 +62,9 @@ class DynamicPropertyAggregationFormula extends DynamicPropertyBase {
     ctx.appendParseSelect(parsedFormula, alias);
   }
 
+  @Override
+  public boolean isDbLob() {
+    return false;
+  }
+
 }

ebean-core/src/main/java/io/ebeaninternal/server/query/CQueryBuilder.java

@@ -760,6 +760,10 @@ final class CQueryBuilder {
     return dbPlatform.isPlatform(Platform.POSTGRES);
   }
 
+  boolean isPlatformDistinctNoLobs() {
+    return dbPlatform.isPlatform(Platform.DB2); // CHECKME: Also oracle?
+  }
+
   /**
    * Return the 'for update' FROM hint (sql server).
    */

ebean-core/src/main/java/io/ebeaninternal/server/query/STreeProperty.java

@@ -28,6 +28,11 @@ public interface STreeProperty extends ScalarDataReader<Object> {
    * Return true if the property is the Id.
    */
   boolean isId();
+  
+  /**
+   * Returns true, if this is a lob property from db-perspective.
+   */
+  boolean isDbLob();
 
   /**
    * Return true if the property is an embedded type.

ebean-core/src/main/java/io/ebeaninternal/server/query/SqlTreeNode.java

@@ -78,6 +78,10 @@ interface SqlTreeNode {
    * Create the loader for this node.
    */
   SqlTreeLoad createLoad();
-  
-  default void unselectLobs() {};
+
+  /**
+   * Unselect lobs (for distinct queries on DB2 and Oracle).
+   */
+  default void unselectLobs() {
+  };
 }