Bug: Wrong join in query with @Inheritance and @DbForeignKey

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

@@ -3,6 +3,7 @@ package io.ebeaninternal.server.deploy;
 import io.ebean.bean.EntityBean;
 import io.ebean.bean.PersistenceContext;
 import io.ebeaninternal.server.query.SqlJoinType;
+import io.ebeaninternal.server.query.SqlTreeJoin;
 
 import java.sql.SQLException;
 
@@ -60,11 +61,28 @@ final class AssocOneHelpRefInherit extends AssocOneHelp {
     return ref;
   }
 
-  @Override
   void appendFrom(DbSqlContext ctx, SqlJoinType joinType) {
     // add join to support the discriminator column
     String relativePrefix = ctx.getRelativePrefix(property.name);
-    property.tableJoin.addJoin(joinType, relativePrefix, ctx);
+    ctx.addExtraJoin(new Extra(relativePrefix, joinType));
+  }
+
+  /**
+   * Extra join to support the discriminator column.
+   */
+  final class Extra implements SqlTreeJoin {
+    final String relativePrefix;
+    final SqlJoinType joinType;
+    Extra(String relativePrefix, SqlJoinType joinType) {
+      this.relativePrefix = relativePrefix;
+      this.joinType = joinType;
+    }
+
+    @Override
+    public void addJoin(DbSqlContext ctx) {
+      // add join to support the discriminator column *IF* join is not already present
+      property.tableJoin.addJoin(joinType, relativePrefix, ctx);
+    }
   }
 
   /**

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

@@ -1,6 +1,7 @@
 package io.ebeaninternal.server.deploy;
 
 import io.ebeaninternal.server.query.SqlJoinType;
+import io.ebeaninternal.server.query.SqlTreeJoin;
 
 /**
  * Used to provide context during sql construction.
@@ -133,4 +134,13 @@ public interface DbSqlContext {
    */
   void appendFromForUpdate();
 
+  /**
+   * Delay adding an extra join to support inheritance discriminator in projection (IF required).
+   */
+  void addExtraJoin(SqlTreeJoin treeJoin);
+
+  /**
+   * Add extra joins *IF* required to support inheritance discriminator in projection.
+   */
+  void flushExtraJoins();
 }

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

@@ -7,6 +7,7 @@ import io.ebeaninternal.server.util.ArrayStack;
 
 import java.util.ArrayList;
 import java.util.HashSet;
+import java.util.List;
 
 final class DefaultDbSqlContext implements DbSqlContext {
 
@@ -43,7 +44,9 @@ final class DefaultDbSqlContext implements DbSqlContext {
 
   private String currentPrefix;
 
-  private ArrayList<BeanProperty> encryptedProps;
+  private List<BeanProperty> encryptedProps;
+
+  private List<SqlTreeJoin> extraJoins;
 
   private final CQueryDraftSupport draftSupport;
 
@@ -70,6 +73,24 @@ final class DefaultDbSqlContext implements DbSqlContext {
     return alias.isIncludeSoftDelete();
   }
 
+  @Override
+  public void addExtraJoin(SqlTreeJoin treeJoin) {
+    if (extraJoins == null) {
+      extraJoins = new ArrayList<>();
+    }
+    extraJoins.add(treeJoin);
+  }
+
+  @Override
+  public void flushExtraJoins() {
+    if (extraJoins != null) {
+      for (SqlTreeJoin extra : extraJoins) {
+        extra.addJoin(this);
+      }
+      extraJoins = null;
+    }
+  }
+
   @Override
   public void appendFromForUpdate() {
     if (fromForUpdate != null) {

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

@@ -256,7 +256,7 @@ public final class SqlTreeBuilder {
       }
       addManyWhereJoins(myJoinList);
     }
-    extraProps.forEach(props::add);
+    extraProps.forEach(props::add); //addExtra
 
     if (!rawSql && manyWhereJoins.isFormulaWithJoin(prefix)) {
       for (String property : manyWhereJoins.getFormulaJoinProperties(prefix)) {

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

@@ -0,0 +1,15 @@
+package io.ebeaninternal.server.query;
+
+import io.ebeaninternal.server.deploy.DbSqlContext;
+
+/**
+ * Extra Sql joins conditionally added if required (after children are joined).
+ */
+public interface SqlTreeJoin {
+
+  /**
+   * Add the extra join if required.
+   */
+  void addJoin(DbSqlContext ctx);
+
+}

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

@@ -279,18 +279,16 @@ class SqlTreeNodeBean implements SqlTreeNode {
     ctx.pushTableAlias(prefix);
 
     baseTableAlias = ctx.getTableAlias(prefix);
-
     // join and return SqlJoinType to use for child joins
     joinType = appendFromBaseTable(ctx, joinType);
-
     for (STreeProperty property : properties) {
       // usually nothing... except for 1-1 Exported
       property.appendFrom(ctx, joinType, null);
     }
-
     for (SqlTreeNode child : children) {
       child.appendFrom(ctx, joinType);
     }
+    ctx.flushExtraJoins();
     ctx.popTableAlias();
     ctx.popJoin();
   }