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() {
+  };
 }

ebean-test/src/test/java/org/tests/json/TestJsonMapBasic.java

@@ -3,13 +3,18 @@ package org.tests.json;
 import io.ebean.BaseTestCase;
 import io.ebean.DB;
 import io.ebean.Query;
+import io.ebean.annotation.ForPlatform;
+import io.ebean.annotation.Platform;
 import io.ebean.test.LoggedSql;
 import io.ebean.text.json.EJson;
+
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 import org.tests.model.json.EBasicJsonMap;
 import org.tests.model.json.EBasicJsonMapDetail;
 
 import java.io.IOException;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -18,15 +23,19 @@ import static org.junit.jupiter.api.Assertions.assertEquals;
 
 public class TestJsonMapBasic extends BaseTestCase {
 
-  @Test
-  public void whereManyPredicate() {
+  private final EBasicJsonMap bean = new EBasicJsonMap();;
 
-    if (!isPostgres()) {
-      // testing postgres specific select distinct on clause
-      return;
+  @AfterEach
+  void cleanup() {
+    if (bean != null && bean.getId() != null) {
+      DB.delete(EBasicJsonMap.class, bean.getId());
     }
+  }
+
+  @Test
+  @ForPlatform(Platform.POSTGRES)
+  public void whereManyPredicatePg() {
 
-    EBasicJsonMap bean = new EBasicJsonMap();
     bean.setName("own1");
     bean.getDetails().add(new EBasicJsonMapDetail("detail1"));
     bean.getDetails().add(new EBasicJsonMapDetail("detail2"));
@@ -50,6 +59,36 @@ public class TestJsonMapBasic extends BaseTestCase {
     assertThat(query2.getGeneratedSql()).contains("select distinct on (t0.id) ");
   }
 
+  @Test
+  @ForPlatform(Platform.DB2)
+  public void whereManyPredicateDb2() {
+
+    Map<String, Object> m1 = new HashMap<>();
+    m1.put("foo", "bar");
+    bean.setContent(m1);
+    bean.setName("own1");
+    bean.getDetails().add(new EBasicJsonMapDetail("db2-detail1"));
+    bean.getDetails().add(new EBasicJsonMapDetail("db2-detail2"));
+
+    DB.save(bean);
+    Query<EBasicJsonMap> query1 = DB.find(EBasicJsonMap.class).select("*").fetch("details").where()
+        .startsWith("details.name", "db2-detail").query();
+
+    List<EBasicJsonMap> lst = query1.findList();
+
+    assertThat(query1.getGeneratedSql()).contains("select distinct t0.id, t0.name, t0.version,")
+        .doesNotContain("content");
+    assertThat(lst).hasSize(1);
+    assertThat(lst.get(0).getContent()).containsEntry("foo", "bar");
+
+    Query<EBasicJsonMap> query2 = DB.find(EBasicJsonMap.class).where().startsWith("details.name", "db2-detail")
+        .query();
+    query2.findList();
+
+    assertThat(query2.getGeneratedSql()).contains("select distinct t0.id, t0.name, t0.version from");
+
+  }
+
   @Test
   public void testInsertUpdateDelete() throws IOException {
 
@@ -58,7 +97,6 @@ public class TestJsonMapBasic extends BaseTestCase {
 
     Map<String, Object> content = EJson.parseObject(s0);
 
-    EBasicJsonMap bean = new EBasicJsonMap();
     bean.setName("one");
     bean.setContent(content);
 
@@ -106,7 +144,6 @@ public class TestJsonMapBasic extends BaseTestCase {
     String s0 = "{\"docId\":22,\"contentId\":\"initialDoc\"}";
     Map<String, Object> content = EJson.parseObject(s0);
 
-    EBasicJsonMap bean = new EBasicJsonMap();
     bean.setName("one");
     bean.setContent(content);
 
@@ -133,6 +170,5 @@ public class TestJsonMapBasic extends BaseTestCase {
     assertThat(content2.get("contentId")).isEqualTo("updatedDoc222");
     assertThat(content2.get("docId")).isEqualTo(222L);
 
-    DB.delete(found);
   }
 }