#1740 and #1744 Don't include the discriminator column on Inheritance query on a type that has no sub-types

Fix for #1740

src/main/java/io/ebeaninternal/server/deploy/AssocOneHelpRefInherit.java

@@ -74,7 +74,7 @@ class AssocOneHelpRefInherit extends AssocOneHelp {
   @Override
   void appendSelect(DbSqlContext ctx, boolean subQuery) {
 
-    if (!subQuery) {
+    if (!subQuery && inherit.hasChildren()) {
       // add discriminator column
       String relativePrefix = ctx.getRelativePrefix(property.getName());
       String tableAlias = ctx.getTableAlias(relativePrefix);

src/main/java/io/ebeaninternal/server/deploy/InheritInfo.java

@@ -6,8 +6,8 @@ import io.ebeaninternal.server.deploy.id.IdBinder;
 import io.ebeaninternal.server.deploy.parse.DeployInheritInfo;
 import io.ebeaninternal.server.query.SqlTreeProperties;
 
-import java.lang.reflect.Modifier;
 import javax.persistence.PersistenceException;
+import java.lang.reflect.Modifier;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -175,6 +175,16 @@ public class InheritInfo {
     return children;
   }
 
+  /**
+   * Return true if this node has children.
+   * <p>
+   * When an inheritance node has no children then we don't need
+   * the discriminator column as the type is effectively known.
+   */
+  public boolean hasChildren() {
+    return !children.isEmpty();
+  }
+
   /**
    * Get the bean property additionally looking in the sub types.
    */
@@ -200,7 +210,6 @@ public class InheritInfo {
 
     for (InheritInfo childInfo : children) {
       selectProps.add(childInfo.descriptor.propertiesLocal());
-
       childInfo.addChildrenProperties(selectProps);
     }
   }
@@ -209,9 +218,10 @@ public class InheritInfo {
    * Return the associated InheritInfo for this DB row read.
    */
   public InheritInfo readType(DbReadContext ctx) throws SQLException {
-
-    String discValue = ctx.getDataReader().getString();
-    return readType(discValue);
+    if (!hasChildren()) {
+      return this;
+    }
+    return readType(ctx.getDataReader().getString());
   }
 
   /**
@@ -327,7 +337,6 @@ public class InheritInfo {
    * Return the derived where for the discriminator.
    */
   public String getWhere() {
-
     return where;
   }
 

src/main/java/io/ebeaninternal/server/deploy/parse/DeployInheritInfo.java

@@ -199,9 +199,7 @@ public class DeployInheritInfo {
   public String getWhere() {
 
     List<Object> discList = new ArrayList<>();
-
     appendDiscriminator(discList);
-
     return buildWhereLiteral(discList);
   }
 

src/main/java/io/ebeaninternal/server/query/SqlTreeNodeBean.java

@@ -543,10 +543,9 @@ class SqlTreeNodeBean implements SqlTreeNode {
     }
 
     if (readId) {
-      if (!subQuery && inheritInfo != null) {
+      if (!subQuery && inheritInfo != null && inheritInfo.hasChildren()) {
         ctx.appendColumn(inheritInfo.getDiscriminatorColumn());
       }
-
       appendSelectId(ctx, idBinder.getBeanProperty());
     }
     appendSelect(ctx, subQuery, properties);