#483 - ENH: Draftable - Add FK from live table back to draft table (for top level @Draftable tables)

src/main/java/com/avaje/ebean/dbmigration/model/build/ModelBuildContext.java

@@ -10,6 +10,7 @@ import com.avaje.ebeaninternal.server.deploy.BeanProperty;
 import com.avaje.ebeaninternal.server.type.ScalarType;
 
 import java.util.Collection;
+import java.util.List;
 
 /**
  * The context used during DDL generation.
@@ -134,11 +135,22 @@ public class ModelBuildContext {
   /**
    * Create the draft table for a given table.
    */
-  public void createDraft(MTable table) {
+  public void createDraft(MTable table, boolean draftable) {
 
     MTable draftTable = table.createDraftTable();
     draftTable.setPkName(primaryKeyName(draftTable.getName()));
 
+    if (draftable) {
+      // Add a FK from @Draftable live table back to it's draft table)
+      List<MColumn> pkCols = table.primaryKeyColumns();
+      if (pkCols.size() == 1) {
+        // only doing this for single column PK at this stage
+        MColumn pk = pkCols.get(0);
+        pk.setReferences(draftTable.getName() + "." + pk.getName());
+        pk.setForeignKeyName(foreignKeyConstraintName(table.getName(), pk.getName(), 0));
+      }
+    }
+
     int fkCount = 0;
     int ixCount = 0;
     int uqCount = 0;

src/main/java/com/avaje/ebean/dbmigration/model/build/ModelBuildIntersectionTable.java

@@ -44,7 +44,7 @@ public class ModelBuildIntersectionTable {
     buildFkConstraints();
 
     if (manyProp.getTargetDescriptor().isDraftable()) {
-      ctx.createDraft(intersectionTable);
+      ctx.createDraft(intersectionTable, false);
     }
 
 	}

src/main/java/com/avaje/ebean/dbmigration/model/build/ModelBuildPropertyVisitor.java

@@ -112,7 +112,7 @@ public class ModelBuildPropertyVisitor extends BaseTablePropertyVisitor {
   private void addDraftTable() {
     if (beanDescriptor.isDraftable() || beanDescriptor.isDraftableElement()) {
       // create a 'Draft' table which looks very similar (change PK, FK etc)
-      ctx.createDraft(table);
+      ctx.createDraft(table, !beanDescriptor.isDraftableElement());
     }
   }
 

src/main/java/com/avaje/ebeaninternal/server/core/PersistRequestBean.java

@@ -151,12 +151,29 @@ public final class PersistRequestBean<T> extends PersistRequest implements BeanP
     }
     this.concurrencyMode = beanDescriptor.getConcurrencyMode(intercept);
     this.publish = publish;
-    if (!publish && beanDescriptor.isDraftable()) {
+    if (isMarkDraftDirty(publish)) {
       beanDescriptor.setDraftDirty(entityBean, true);
     }
     this.dirty = intercept.isDirty();
   }
 
+  /**
+   * Return true if the draftDirty property should be set to true for this request.
+   */
+  private boolean isMarkDraftDirty(boolean publish) {
+    return !publish && type != Type.DELETE && beanDescriptor.isDraftable();
+  }
+
+  /**
+   * Set the transaction from prior persist request.
+   * Only used when hard deleting draft & associated live beans.
+   */
+  public void setTrans(SpiTransaction transaction) {
+    this.transaction = transaction;
+    this.createdTransaction = false;
+    this.persistCascade = transaction.isPersistCascade();
+  }
+
   /**
    * Init the transaction and also check for batch on cascade escalation.
    */
@@ -437,6 +454,21 @@ public final class PersistRequestBean<T> extends PersistRequest implements BeanP
     return beanDescriptor.isDraftable();
   }
 
+  /**
+   * Return true if this request is a hard delete of a draftable bean.
+   * If this is true Ebean is expected to auto-publish and delete the associated live bean.
+   */
+  public boolean isHardDeleteDraft() {
+    if (type == Type.DELETE && beanDescriptor.isDraftable() && !beanDescriptor.isDraftableElement()) {
+      // deleting a top level draftable bean
+      if (!beanDescriptor.isDraftInstance(entityBean)) {
+        throw new PersistenceException("Explicit Delete is not allowed on a 'live' bean - only draft beans");
+      }
+      return true;
+    }
+    return false;
+  }
+
   /**
    * Checks for @Draftable entity beans with @Draft property that the bean is a 'draft'.
    * Save or Update is not allowed to execute using 'live' beans - must use publish().

src/main/java/com/avaje/ebeaninternal/server/persist/DefaultPersister.java

@@ -502,21 +502,31 @@ public final class DefaultPersister implements Persister {
   public boolean delete(EntityBean bean, Transaction t, boolean permanent) {
 
     Type deleteType = permanent ? Type.DELETE_PERMANENT : Type.DELETE;
-    PersistRequestBean<EntityBean> request = createRequest(bean, t, deleteType);
-    boolean deleted = deleteRequest(request);
+    PersistRequestBean<EntityBean> originalRequest = createRequest(bean, t, deleteType);
 
-    if (request.isDraftable() && request.getType() == Type.DELETE) {
-      // we have just deleting a draft bean so now we need to delete the
-      // associated 'live' bean. This is effectively an 'automatic publish'.
-      deleteRequest(createPublishRequest(request.createReference(), t, Type.DELETE_PERMANENT, true));
+    if (originalRequest.isHardDeleteDraft()) {
+      // a hard delete of a draftable bean so first we need to  delete the associated 'live' bean
+      // due to FK constraint and then after that execute the original delete of the draft bean
+      return deleteRequest(createPublishRequest(originalRequest.createReference(), t, Type.DELETE_PERMANENT, true), originalRequest);
+
+    } else {
+      // normal delete or soft delete
+      return deleteRequest(originalRequest);
     }
-    return deleted;
   }
 
   /**
    * Execute the delete request returning true if a delete occurred.
    */
   private boolean deleteRequest(PersistRequestBean<?> req) {
+    return deleteRequest(req, null);
+  }
+
+  /**
+   * Execute the delete request support a second delete request for live and draft permanent delete.
+   * A common transaction is used across both requests.
+   */
+  private boolean deleteRequest(PersistRequestBean<?> req, PersistRequestBean<?> draftReq) {
 
     if (req.isRegisteredForDeleteBean()) {
       // skip deleting bean. Used where cascade is on
@@ -530,6 +540,11 @@ public final class DefaultPersister implements Persister {
     try {
       req.initTransIfRequiredWithBatchCascade();
       boolean deleted = delete(req);
+      if (draftReq != null) {
+        // delete the 'draft' bean ('live' bean deleted first)
+        draftReq.setTrans(req.getTransaction());
+        deleted = delete(draftReq);
+      }
       req.commitTransIfRequired();
       req.flushBatchOnCascade();