Add BillingVKey to restore symmetric VKey in GracePeriodBase (#902)

* Use PollMessageVKey to replace VKey<PollMessage> in DomainBase

* Revert changes to DomainContent

* Use BillingVKey in GracePeriodBase to restore symmetric vkey

* Rebase on HEAD

core/src/main/java/google/registry/flows/domain/DomainCreateFlow.java

@@ -110,7 +110,6 @@ import google.registry.model.reporting.DomainTransactionRecord;
 import google.registry.model.reporting.DomainTransactionRecord.TransactionReportField;
 import google.registry.model.reporting.HistoryEntry;
 import google.registry.model.reporting.IcannReportingTypes.ActivityReportField;
-import google.registry.persistence.DomainHistoryVKey;
 import google.registry.persistence.VKey;
 import google.registry.tmch.LordnTaskUtils;
 import java.util.Optional;
@@ -372,7 +371,7 @@ public class DomainCreateFlow implements TransactionalFlow {
         && TokenType.SINGLE_USE.equals(allocationToken.get().getTokenType())) {
       entitiesToSave.add(
           allocationTokenFlowUtils.redeemToken(
-              allocationToken.get(), DomainHistoryVKey.create(Key.create(historyEntry))));
+              allocationToken.get(), HistoryEntry.createVKey(Key.create(historyEntry))));
     }
     enqueueTasks(newDomain, hasSignedMarks, hasClaimsNotice);
 

core/src/main/java/google/registry/flows/domain/token/AllocationTokenFlowUtils.java

@@ -32,7 +32,8 @@ import google.registry.model.domain.token.AllocationToken;
 import google.registry.model.domain.token.AllocationToken.TokenStatus;
 import google.registry.model.domain.token.AllocationToken.TokenType;
 import google.registry.model.registry.Registry;
-import google.registry.persistence.DomainHistoryVKey;
+import google.registry.model.reporting.HistoryEntry;
+import google.registry.persistence.VKey;
 import java.util.List;
 import java.util.Optional;
 import javax.inject.Inject;
@@ -107,7 +108,7 @@ public class AllocationTokenFlowUtils {
 
   /** Redeems a SINGLE_USE {@link AllocationToken}, returning the redeemed copy. */
   public AllocationToken redeemToken(
-      AllocationToken token, DomainHistoryVKey redemptionHistoryEntry) {
+      AllocationToken token, VKey<? extends HistoryEntry> redemptionHistoryEntry) {
     checkArgument(
         TokenType.SINGLE_USE.equals(token.getTokenType()),
         "Only SINGLE_USE tokens can be marked as redeemed");

core/src/main/java/google/registry/model/domain/GracePeriod.java

@@ -23,6 +23,8 @@ import google.registry.model.billing.BillingEvent;
 import google.registry.model.billing.BillingEvent.Recurring;
 import google.registry.model.domain.rgp.GracePeriodStatus;
 import google.registry.model.ofy.ObjectifyService;
+import google.registry.persistence.BillingVKey.BillingEventVKey;
+import google.registry.persistence.BillingVKey.BillingRecurrenceVKey;
 import google.registry.persistence.VKey;
 import google.registry.schema.replay.DatastoreAndSqlEntity;
 import javax.annotation.Nullable;
@@ -82,10 +84,8 @@ public class GracePeriod extends GracePeriodBase implements DatastoreAndSqlEntit
     instance.domainRepoId = checkArgumentNotNull(domainRepoId);
     instance.expirationTime = checkArgumentNotNull(expirationTime);
     instance.clientId = checkArgumentNotNull(clientId);
-    instance.billingEventOneTime = billingEventOneTime;
+    instance.billingEventOneTime = BillingEventVKey.create(billingEventOneTime);
-    instance.billingEventOneTimeHistoryId = DomainBase.getHistoryId(billingEventOneTime);
+    instance.billingEventRecurring = BillingRecurrenceVKey.create(billingEventRecurring);
-    instance.billingEventRecurring = billingEventRecurring;
-    instance.billingEventRecurringHistoryId = DomainBase.getHistoryId(billingEventRecurring);
     return instance;
   }
 
@@ -178,7 +178,6 @@ public class GracePeriod extends GracePeriodBase implements DatastoreAndSqlEntit
   public GracePeriod cloneAfterOfyLoad(String domainRepoId) {
     GracePeriod clone = clone(this);
     clone.domainRepoId = checkArgumentNotNull(domainRepoId);
-    clone.restoreHistoryIds();
     return clone;
   }
 
@@ -190,7 +189,7 @@ public class GracePeriod extends GracePeriodBase implements DatastoreAndSqlEntit
    */
   public GracePeriod cloneWithRecurringBillingEvent(VKey<BillingEvent.Recurring> recurring) {
     GracePeriod clone = clone(this);
-    clone.billingEventRecurring = recurring;
+    clone.billingEventRecurring = BillingRecurrenceVKey.create(recurring);
     return clone;
   }
 
@@ -232,9 +231,7 @@ public class GracePeriod extends GracePeriodBase implements DatastoreAndSqlEntit
       instance.expirationTime = gracePeriod.expirationTime;
       instance.clientId = gracePeriod.clientId;
       instance.billingEventOneTime = gracePeriod.billingEventOneTime;
-      instance.billingEventOneTimeHistoryId = gracePeriod.billingEventOneTimeHistoryId;
       instance.billingEventRecurring = gracePeriod.billingEventRecurring;
-      instance.billingEventRecurringHistoryId = gracePeriod.billingEventRecurringHistoryId;
       return instance;
     }
   }

core/src/main/java/google/registry/model/domain/GracePeriodBase.java

@@ -14,14 +14,14 @@
 
 package google.registry.model.domain;
 
-import com.googlecode.objectify.Key;
 import com.googlecode.objectify.annotation.Embed;
 import com.googlecode.objectify.annotation.Ignore;
 import google.registry.model.ImmutableObject;
 import google.registry.model.ModelUtils;
 import google.registry.model.billing.BillingEvent;
-import google.registry.model.billing.BillingEvent.OneTime;
 import google.registry.model.domain.rgp.GracePeriodStatus;
+import google.registry.persistence.BillingVKey.BillingEventVKey;
+import google.registry.persistence.BillingVKey.BillingRecurrenceVKey;
 import google.registry.persistence.VKey;
 import java.lang.reflect.Field;
 import java.util.LinkedHashMap;
@@ -68,24 +68,16 @@ public class GracePeriodBase extends ImmutableObject {
    * billingEventRecurring}) or for redemption grace periods (since deletes have no cost).
    */
   // NB: Would @IgnoreSave(IfNull.class), but not allowed for @Embed collections.
-  @Column(name = "billing_event_id")
+  @Access(AccessType.FIELD)
-  VKey<OneTime> billingEventOneTime = null;
+  BillingEventVKey billingEventOneTime = null;
-
-  @Ignore
-  @Column(name = "billing_event_history_id")
-  Long billingEventOneTimeHistoryId;
 
   /**
    * The recurring billing event corresponding to the action that triggered this grace period, if
    * applicable - i.e. if the action was an autorenew - or null in all other cases.
    */
   // NB: Would @IgnoreSave(IfNull.class), but not allowed for @Embed collections.
-  @Column(name = "billing_recurrence_id")
+  @Access(AccessType.FIELD)
-  VKey<BillingEvent.Recurring> billingEventRecurring = null;
+  BillingRecurrenceVKey billingEventRecurring = null;
-
-  @Ignore
-  @Column(name = "billing_recurrence_history_id")
-  Long billingEventRecurringHistoryId;
 
   public long getGracePeriodId() {
     return gracePeriodId;
@@ -123,8 +115,7 @@ public class GracePeriodBase extends ImmutableObject {
    * period is not AUTO_RENEW.
    */
   public VKey<BillingEvent.OneTime> getOneTimeBillingEvent() {
-    restoreOfyKeys();
+    return billingEventOneTime == null ? null : billingEventOneTime.createVKey();
-    return billingEventOneTime;
   }
 
   /**
@@ -132,18 +123,7 @@ public class GracePeriodBase extends ImmutableObject {
    * period is AUTO_RENEW.
    */
   public VKey<BillingEvent.Recurring> getRecurringBillingEvent() {
-    restoreOfyKeys();
+    return billingEventRecurring == null ? null : billingEventRecurring.createVKey();
-    return billingEventRecurring;
-  }
-
-  /**
-   * Restores history ids for composite VKeys after a load from datastore.
-   *
-   * <p>For use by DomainContent.load() ONLY.
-   */
-  protected void restoreHistoryIds() {
-    billingEventOneTimeHistoryId = DomainBase.getHistoryId(billingEventOneTime);
-    billingEventRecurringHistoryId = DomainBase.getHistoryId(billingEventRecurring);
   }
 
   /**
@@ -152,7 +132,6 @@ public class GracePeriodBase extends ImmutableObject {
    */
   @Override
   protected Map<Field, Object> getSignificantFields() {
-    restoreOfyKeys();
     // Can't use streams or ImmutableMap because we can have null values.
     Map<Field, Object> result = new LinkedHashMap();
     for (Map.Entry<Field, Object> entry : ModelUtils.getFieldValues(this).entrySet()) {
@@ -162,33 +141,4 @@ public class GracePeriodBase extends ImmutableObject {
     }
     return result;
   }
-
-  /**
-   * Restores Ofy keys in the billing events.
-   *
-   * <p>This must be called by all methods that access the one time or recurring billing event keys.
-   * When the billing event keys are loaded from SQL, they are loaded as asymmetric keys because the
-   * database columns that we load them from do not contain all of the information necessary to
-   * reconsitute the Ofy side of the key. In other cases, we restore the Ofy key during the
-   * hibernate {@link javax.persistence.PostLoad} method from the other fields of the object, but we
-   * have been unable to make this work with hibernate's internal persistence model in this case
-   * because the {@link GracePeriod}'s hash code is evaluated prior to these calls, and would be
-   * invalidated by changing the fields.
-   */
-  private final synchronized void restoreOfyKeys() {
-    if (billingEventOneTime != null && !billingEventOneTime.maybeGetOfyKey().isPresent()) {
-      billingEventOneTime =
-          DomainBase.restoreOfyFrom(
-              Key.create(DomainBase.class, domainRepoId),
-              billingEventOneTime,
-              billingEventOneTimeHistoryId);
-    }
-    if (billingEventRecurring != null && !billingEventRecurring.maybeGetOfyKey().isPresent()) {
-      billingEventRecurring =
-          DomainBase.restoreOfyFrom(
-              Key.create(DomainBase.class, domainRepoId),
-              billingEventRecurring,
-              billingEventRecurringHistoryId);
-    }
-  }
 }

core/src/main/java/google/registry/model/domain/token/AllocationToken.java

@@ -111,9 +111,9 @@ public class AllocationToken extends BackupGroupRoot implements Buildable, Datas
   @Nullable
   @Index
   @AttributeOverrides({
-    @AttributeOverride(name = "domainRepoId", column = @Column(name = "redemption_domain_repo_id")),
+    @AttributeOverride(name = "repoId", column = @Column(name = "redemption_domain_repo_id")),
     @AttributeOverride(
-        name = "domainHistoryId",
+        name = "historyRevisionId",
         column = @Column(name = "redemption_domain_history_id"))
   })
   DomainHistoryVKey redemptionHistoryEntry;
@@ -192,8 +192,9 @@ public class AllocationToken extends BackupGroupRoot implements Buildable, Datas
     return token;
   }
 
-  public Optional<VKey<HistoryEntry>> getRedemptionHistoryEntry() {
+  public Optional<VKey<? extends HistoryEntry>> getRedemptionHistoryEntry() {
-    return Optional.ofNullable(redemptionHistoryEntry);
+    return Optional.ofNullable(
+        redemptionHistoryEntry == null ? null : redemptionHistoryEntry.createDomainHistoryVKey());
   }
 
   public boolean isRedeemed() {
@@ -291,9 +292,10 @@ public class AllocationToken extends BackupGroupRoot implements Buildable, Datas
       return this;
     }
 
-    public Builder setRedemptionHistoryEntry(DomainHistoryVKey redemptionHistoryEntry) {
+    public Builder setRedemptionHistoryEntry(VKey<? extends HistoryEntry> redemptionHistoryEntry) {
-      getInstance().redemptionHistoryEntry =
       checkArgumentNotNull(redemptionHistoryEntry, "Redemption history entry must not be null");
+      getInstance().redemptionHistoryEntry =
+          DomainHistoryVKey.create(redemptionHistoryEntry.getOfyKey());
       return this;
     }
 

core/src/main/java/google/registry/model/ofy/ObjectifyService.java

@@ -42,8 +42,8 @@ import google.registry.model.translators.CidrAddressBlockTranslatorFactory;
 import google.registry.model.translators.CommitLogRevisionsTranslatorFactory;
 import google.registry.model.translators.CreateAutoTimestampTranslatorFactory;
 import google.registry.model.translators.CurrencyUnitTranslatorFactory;
-import google.registry.model.translators.DomainHistoryVKeyTranslatorFactory;
 import google.registry.model.translators.DurationTranslatorFactory;
+import google.registry.model.translators.EppHistoryVKeyTranslatorFactory;
 import google.registry.model.translators.InetAddressTranslatorFactory;
 import google.registry.model.translators.ReadableInstantUtcTranslatorFactory;
 import google.registry.model.translators.UpdateAutoTimestampTranslatorFactory;
@@ -128,7 +128,7 @@ public class ObjectifyService {
             new CreateAutoTimestampTranslatorFactory(),
             new CurrencyUnitTranslatorFactory(),
             new DurationTranslatorFactory(),
-            new DomainHistoryVKeyTranslatorFactory(),
+            new EppHistoryVKeyTranslatorFactory(),
             new InetAddressTranslatorFactory(),
             new MoneyStringTranslatorFactory(),
             new ReadableInstantUtcTranslatorFactory(),

core/src/main/java/google/registry/model/translators/DomainHistoryVKeyTranslatorFactory.java

@@ -1,48 +0,0 @@
-// Copyright 2020 The Nomulus Authors. All Rights Reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package google.registry.model.translators;
-
-import com.google.appengine.api.datastore.Key;
-import google.registry.persistence.DomainHistoryVKey;
-import javax.annotation.Nullable;
-
-/** Translator factory for {@link DomainHistoryVKey}. */
-public class DomainHistoryVKeyTranslatorFactory
-    extends AbstractSimpleTranslatorFactory<DomainHistoryVKey, Key> {
-
-  public DomainHistoryVKeyTranslatorFactory() {
-    super(DomainHistoryVKey.class);
-  }
-
-  @Override
-  SimpleTranslator<DomainHistoryVKey, Key> createTranslator() {
-    return new SimpleTranslator<DomainHistoryVKey, Key>() {
-
-      @Nullable
-      @Override
-      public DomainHistoryVKey loadValue(@Nullable Key datastoreValue) {
-        return datastoreValue == null
-            ? null
-            : DomainHistoryVKey.create(com.googlecode.objectify.Key.create(datastoreValue));
-      }
-
-      @Nullable
-      @Override
-      public Key saveValue(@Nullable DomainHistoryVKey pojoValue) {
-        return pojoValue == null ? null : pojoValue.getOfyKey().getRaw();
-      }
-    };
-  }
-}

core/src/main/java/google/registry/model/translators/EppHistoryVKeyTranslatorFactory.java

@@ -0,0 +1,110 @@
+// Copyright 2020 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.model.translators;
+
+import static com.google.common.collect.ImmutableMap.toImmutableMap;
+import static java.util.function.Function.identity;
+
+import com.google.appengine.api.datastore.Key;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import google.registry.persistence.BillingVKey.BillingEventVKey;
+import google.registry.persistence.BillingVKey.BillingRecurrenceVKey;
+import google.registry.persistence.DomainHistoryVKey;
+import google.registry.persistence.EppHistoryVKey;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import javax.annotation.Nullable;
+
+/** Translator factory for {@link EppHistoryVKey}. */
+public class EppHistoryVKeyTranslatorFactory
+    extends AbstractSimpleTranslatorFactory<EppHistoryVKey, Key> {
+
+  public EppHistoryVKeyTranslatorFactory() {
+    super(EppHistoryVKey.class);
+  }
+
+  // This map is used when we need to convert the raw Datastore key to its VKey instance. We have
+  // one dedicated VKey class, e.g. DomainHistoryVKey, for each such kind of entity, and we need
+  // a way to map the raw Datastore key to its VKey class. So, we use the kind path as the key of
+  // the map, and the kind path is created by concatenating all the kind strings in a raw Datastore
+  // key, e.g. the map key for ContactPollMessageVKey is "ContactResource/HistoryEntry/PollMessage".
+  @VisibleForTesting
+  static final ImmutableMap<String, Class<? extends EppHistoryVKey>> kindPathToVKeyClass =
+      ImmutableSet.of(DomainHistoryVKey.class, BillingEventVKey.class, BillingRecurrenceVKey.class)
+          .stream()
+          .collect(toImmutableMap(EppHistoryVKeyTranslatorFactory::getKindPath, identity()));
+
+  /**
+   * Gets the kind path string for the given {@link Class}.
+   *
+   * <p>This method calls the getKindPath method on an instance of the given {@link Class} to get
+   * the kind path string.
+   */
+  private static String getKindPath(Class<? extends EppHistoryVKey> clazz) {
+    try {
+      Constructor<?> constructor = clazz.getDeclaredConstructor();
+      constructor.setAccessible(true);
+      Object instance = constructor.newInstance();
+      Method getKindPathMethod = EppHistoryVKey.class.getDeclaredMethod("getKindPath");
+      getKindPathMethod.setAccessible(true);
+      return (String) getKindPathMethod.invoke(instance);
+    } catch (Throwable t) {
+      throw new IllegalStateException(t);
+    }
+  }
+
+  @Override
+  SimpleTranslator<EppHistoryVKey, Key> createTranslator() {
+    return new SimpleTranslator<EppHistoryVKey, Key>() {
+
+      @Nullable
+      @Override
+      public EppHistoryVKey loadValue(@Nullable Key datastoreValue) {
+        if (datastoreValue == null) {
+          return null;
+        } else {
+          com.googlecode.objectify.Key<?> ofyKey =
+              com.googlecode.objectify.Key.create(datastoreValue);
+          String kindPath = EppHistoryVKey.createKindPath(ofyKey);
+          if (kindPathToVKeyClass.containsKey(kindPath)) {
+            Class<? extends EppHistoryVKey> vKeyClass = kindPathToVKeyClass.get(kindPath);
+            try {
+              Method createVKeyMethod =
+                  vKeyClass.getDeclaredMethod("create", com.googlecode.objectify.Key.class);
+              return (EppHistoryVKey) createVKeyMethod.invoke(null, ofyKey);
+            } catch (NoSuchMethodException e) {
+              throw new IllegalStateException(
+                  "Missing static method create(com.googlecode.objectify.Key) on " + vKeyClass);
+            } catch (IllegalAccessException | InvocationTargetException e) {
+              throw new IllegalStateException("Error invoking createVKey on " + vKeyClass, e);
+            }
+          } else {
+            throw new IllegalStateException(
+                "Missing EppHistoryVKey implementation for kind path: " + kindPath);
+          }
+        }
+      }
+
+      @Nullable
+      @Override
+      public Key saveValue(@Nullable EppHistoryVKey pojoValue) {
+        return pojoValue == null ? null : pojoValue.createOfyKey().getRaw();
+      }
+    };
+  }
+}

core/src/main/java/google/registry/persistence/BillingVKey.java

@@ -0,0 +1,134 @@
+// Copyright 2020 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.persistence;
+
+
+import com.googlecode.objectify.Key;
+import google.registry.model.billing.BillingEvent;
+import google.registry.model.billing.BillingEvent.OneTime;
+import google.registry.model.billing.BillingEvent.Recurring;
+import google.registry.model.domain.DomainBase;
+import google.registry.model.reporting.HistoryEntry;
+import javax.annotation.Nullable;
+import javax.persistence.AttributeOverride;
+import javax.persistence.AttributeOverrides;
+import javax.persistence.Column;
+import javax.persistence.Embeddable;
+import javax.persistence.MappedSuperclass;
+
+/** Base class for {@link BillingEvent}'s {@link VKey}. */
+@MappedSuperclass
+public abstract class BillingVKey<K> extends EppHistoryVKey<K, DomainBase> {
+  Long billingId;
+
+  // Hibernate requires a default constructor.
+  BillingVKey() {}
+
+  BillingVKey(String repoId, long historyRevisionId, long billingId) {
+    super(repoId, historyRevisionId);
+    this.billingId = billingId;
+  }
+
+  Key<HistoryEntry> createHistoryEntryKey() {
+    return Key.create(Key.create(DomainBase.class, repoId), HistoryEntry.class, historyRevisionId);
+  }
+
+  @Override
+  public Object createSqlKey() {
+    return billingId;
+  }
+
+  /** VKey class for {@link BillingEvent.OneTime} that belongs to a {@link DomainBase} entity. */
+  @Embeddable
+  @AttributeOverrides({
+    @AttributeOverride(name = "repoId", column = @Column(name = "billing_event_domain_repo_id")),
+    @AttributeOverride(
+        name = "historyRevisionId",
+        column = @Column(name = "billing_event_history_id")),
+    @AttributeOverride(name = "billingId", column = @Column(name = "billing_event_id"))
+  })
+  public static class BillingEventVKey extends BillingVKey<OneTime> {
+
+    // Hibernate requires this default constructor
+    private BillingEventVKey() {}
+
+    private BillingEventVKey(String repoId, long historyRevisionId, long billingEventId) {
+      super(repoId, historyRevisionId, billingEventId);
+    }
+
+    @Override
+    public Key<OneTime> createOfyKey() {
+      return Key.create(createHistoryEntryKey(), BillingEvent.OneTime.class, billingId);
+    }
+
+    /** Creates a {@link BillingEventVKey} instance from the given {@link Key} instance. */
+    public static BillingEventVKey create(@Nullable Key<BillingEvent.OneTime> ofyKey) {
+      if (ofyKey == null) {
+        return null;
+      }
+      long billingEventId = ofyKey.getId();
+      long historyRevisionId = ofyKey.getParent().getId();
+      String repoId = ofyKey.getParent().getParent().getName();
+      return new BillingEventVKey(repoId, historyRevisionId, billingEventId);
+    }
+
+    /** Creates a {@link BillingEventVKey} instance from the given {@link VKey} instance. */
+    public static BillingEventVKey create(@Nullable VKey<BillingEvent.OneTime> vKey) {
+      return vKey == null ? null : create(vKey.getOfyKey());
+    }
+  }
+
+  /** VKey class for {@link BillingEvent.Recurring} that belongs to a {@link DomainBase} entity. */
+  @Embeddable
+  @AttributeOverrides({
+    @AttributeOverride(
+        name = "repoId",
+        column = @Column(name = "billing_recurrence_domain_repo_id")),
+    @AttributeOverride(
+        name = "historyRevisionId",
+        column = @Column(name = "billing_recurrence_history_id")),
+    @AttributeOverride(name = "billingId", column = @Column(name = "billing_recurrence_id"))
+  })
+  public static class BillingRecurrenceVKey extends BillingVKey<Recurring> {
+
+    // Hibernate requires this default constructor
+    private BillingRecurrenceVKey() {}
+
+    private BillingRecurrenceVKey(String repoId, long historyRevisionId, long billingEventId) {
+      super(repoId, historyRevisionId, billingEventId);
+    }
+
+    @Override
+    public Key<Recurring> createOfyKey() {
+      return Key.create(createHistoryEntryKey(), BillingEvent.Recurring.class, billingId);
+    }
+
+    /** Creates a {@link BillingRecurrenceVKey} instance from the given {@link Key} instance. */
+    public static BillingRecurrenceVKey create(@Nullable Key<BillingEvent.Recurring> ofyKey) {
+      if (ofyKey == null) {
+        return null;
+      }
+      long billingEventId = ofyKey.getId();
+      long historyRevisionId = ofyKey.getParent().getId();
+      String repoId = ofyKey.getParent().getParent().getName();
+      return new BillingRecurrenceVKey(repoId, historyRevisionId, billingEventId);
+    }
+
+    /** Creates a {@link BillingRecurrenceVKey} instance from the given {@link VKey} instance. */
+    public static BillingRecurrenceVKey create(@Nullable VKey<BillingEvent.Recurring> vKey) {
+      return vKey == null ? null : create(vKey.getOfyKey());
+    }
+  }
+}

core/src/main/java/google/registry/persistence/DomainHistoryVKey.java

@@ -18,45 +18,44 @@ import static google.registry.util.PreconditionsUtils.checkArgumentNotNull;
 
 import com.googlecode.objectify.Key;
 import google.registry.model.domain.DomainBase;
+import google.registry.model.domain.DomainHistory;
 import google.registry.model.domain.DomainHistory.DomainHistoryId;
 import google.registry.model.reporting.HistoryEntry;
 import javax.persistence.Embeddable;
-import javax.persistence.PostLoad;
 
 /** {@link VKey} for {@link HistoryEntry} which parent is {@link DomainBase}. */
 @Embeddable
-public class DomainHistoryVKey extends VKey<HistoryEntry> {
+public class DomainHistoryVKey extends EppHistoryVKey<HistoryEntry, DomainBase> {
-
-  private String domainRepoId;
-
-  private Long domainHistoryId;
 
   // Hibernate requires a default constructor
   private DomainHistoryVKey() {}
 
-  private DomainHistoryVKey(String domainRepoId, long domainHistoryId) {
+  private DomainHistoryVKey(String repoId, long historyRevisionId) {
-    initWith(domainRepoId, domainHistoryId);
+    super(repoId, historyRevisionId);
   }
 
-  @PostLoad
+  @Override
-  void postLoad() {
+  public Object createSqlKey() {
-    initWith(domainRepoId, domainHistoryId);
+    return new DomainHistoryId(repoId, historyRevisionId);
   }
 
-  private void initWith(String domainRepoId, long domainHistoryId) {
+  @Override
-    this.kind = HistoryEntry.class;
+  public Key<HistoryEntry> createOfyKey() {
-    this.ofyKey =
+    return Key.create(Key.create(DomainBase.class, repoId), HistoryEntry.class, historyRevisionId);
-        Key.create(Key.create(DomainBase.class, domainRepoId), HistoryEntry.class, domainHistoryId);
-    this.sqlKey = new DomainHistoryId(domainRepoId, domainHistoryId);
-    this.domainRepoId = domainRepoId;
-    this.domainHistoryId = domainHistoryId;
   }
 
   /** Creates {@link DomainHistoryVKey} from the given {@link Key} instance. */
-  public static DomainHistoryVKey create(Key<HistoryEntry> ofyKey) {
+  public static DomainHistoryVKey create(Key<? extends HistoryEntry> ofyKey) {
     checkArgumentNotNull(ofyKey, "ofyKey must be specified");
-    String domainRepoId = ofyKey.getParent().getName();
+    String repoId = ofyKey.getParent().getName();
-    long domainHistoryId = ofyKey.getId();
+    long historyRevisionId = ofyKey.getId();
-    return new DomainHistoryVKey(domainRepoId, domainHistoryId);
+    return new DomainHistoryVKey(repoId, historyRevisionId);
+  }
+
+  public VKey<? extends HistoryEntry> createDomainHistoryVKey() {
+    return VKey.create(
+        DomainHistory.class,
+        createSqlKey(),
+        Key.create(Key.create(DomainBase.class, repoId), DomainHistory.class, historyRevisionId));
   }
 }

core/src/main/java/google/registry/persistence/EppHistoryVKey.java

@@ -0,0 +1,107 @@
+// Copyright 2020 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.persistence;
+
+import com.google.common.base.Joiner;
+import com.googlecode.objectify.Key;
+import google.registry.model.EppResource;
+import google.registry.model.ImmutableObject;
+import google.registry.model.reporting.HistoryEntry;
+import google.registry.util.TypeUtils.TypeInstantiator;
+import java.io.Serializable;
+import javax.annotation.Nullable;
+import javax.persistence.Access;
+import javax.persistence.AccessType;
+import javax.persistence.MappedSuperclass;
+
+/**
+ * Base class for {@link VKey} which ofyKey has a {@link HistoryEntry} key as its parent and a key
+ * for EPP resource as its grandparent.
+ *
+ * <p>For such a {@link VKey}, we need to provide two type parameters to indicate the type of {@link
+ * VKey} itself and the type of EPP resource respectively.
+ *
+ * @param <K> type of the {@link VKey}
+ * @param <E> type of the EPP resource that the key belongs to
+ */
+@MappedSuperclass
+@Access(AccessType.FIELD)
+public abstract class EppHistoryVKey<K, E extends EppResource> extends ImmutableObject
+    implements Serializable {
+
+  private static final long serialVersionUID = -3906580677709539818L;
+
+  String repoId;
+
+  Long historyRevisionId;
+
+  // Hibernate requires a default constructor.
+  EppHistoryVKey() {}
+
+  EppHistoryVKey(String repoId, long historyRevisionId) {
+    this.repoId = repoId;
+    this.historyRevisionId = historyRevisionId;
+  }
+
+  /**
+   * Returns the kind path for the ofyKey in this instance.
+   *
+   * <p>This method is only used reflectively by {@link EppHistoryVKeyTranslatorFactory} to get the
+   * kind path for a given {@link EppHistoryVKey} instance so it is marked as a private method.
+   *
+   * @see #createKindPath(Key)
+   */
+  @SuppressWarnings("unused")
+  private String getKindPath() {
+    String eppKind = Key.getKind(new TypeInstantiator<E>(getClass()) {}.getExactType());
+    String keyKind = Key.getKind(new TypeInstantiator<K>(getClass()) {}.getExactType());
+    if (keyKind.equals(Key.getKind(HistoryEntry.class))) {
+      return createKindPath(eppKind, keyKind);
+    } else {
+      return createKindPath(eppKind, Key.getKind(HistoryEntry.class), keyKind);
+    }
+  }
+
+  /**
+   * Creates the kind path for the given ofyKey}.
+   *
+   * <p>The kind path is a string including all kind names(delimited by slash) of a hierarchical
+   * {@link Key}, e.g., the kind path for BillingEvent.OneTime is "DomainBase/HistoryEntry/OneTime".
+   */
+  @Nullable
+  public static String createKindPath(@Nullable Key<?> ofyKey) {
+    if (ofyKey == null) {
+      return null;
+    } else if (ofyKey.getParent() == null) {
+      return ofyKey.getKind();
+    } else {
+      return createKindPath(createKindPath(ofyKey.getParent()), ofyKey.getKind());
+    }
+  }
+
+  private static String createKindPath(String... kinds) {
+    return Joiner.on("/").join(kinds);
+  }
+
+  /** Creates a {@link VKey} from this instance. */
+  public VKey<K> createVKey() {
+    Class<K> vKeyType = new TypeInstantiator<K>(getClass()) {}.getExactType();
+    return VKey.create(vKeyType, createSqlKey(), createOfyKey());
+  }
+
+  public abstract Object createSqlKey();
+
+  public abstract Key<K> createOfyKey();
+}

core/src/test/java/google/registry/flows/domain/DomainCheckFlowTest.java

@@ -71,7 +71,6 @@ import google.registry.model.registry.Registry;
 import google.registry.model.registry.Registry.TldState;
 import google.registry.model.registry.label.ReservedList;
 import google.registry.model.reporting.HistoryEntry;
-import google.registry.persistence.DomainHistoryVKey;
 import org.joda.money.CurrencyUnit;
 import org.joda.money.Money;
 import org.joda.time.DateTime;
@@ -169,7 +168,7 @@ class DomainCheckFlowTest extends ResourceCheckFlowTestCase<DomainCheckFlow, Dom
         new AllocationToken.Builder()
             .setToken("abc123")
             .setTokenType(SINGLE_USE)
-            .setRedemptionHistoryEntry(DomainHistoryVKey.create(historyEntryKey))
+            .setRedemptionHistoryEntry(HistoryEntry.createVKey(historyEntryKey))
             .build());
     doCheckTest(
         create(false, "example1.tld", "In use"),

core/src/test/java/google/registry/flows/domain/DomainCreateFlowTest.java

@@ -162,7 +162,6 @@ import google.registry.model.reporting.DomainTransactionRecord;
 import google.registry.model.reporting.DomainTransactionRecord.TransactionReportField;
 import google.registry.model.reporting.HistoryEntry;
 import google.registry.monitoring.whitebox.EppMetric;
-import google.registry.persistence.DomainHistoryVKey;
 import google.registry.testing.ReplayExtension;
 import google.registry.testing.TaskQueueHelper.TaskMatcher;
 import java.math.BigDecimal;
@@ -505,7 +504,7 @@ class DomainCreateFlowTest extends ResourceFlowTestCase<DomainCreateFlow, Domain
         new AllocationToken.Builder()
             .setToken("abc123")
             .setTokenType(SINGLE_USE)
-            .setRedemptionHistoryEntry(DomainHistoryVKey.create(historyEntryKey))
+            .setRedemptionHistoryEntry(HistoryEntry.createVKey(historyEntryKey))
             .build());
     clock.advanceOneMilli();
     EppException thrown =
@@ -528,7 +527,7 @@ class DomainCreateFlowTest extends ResourceFlowTestCase<DomainCreateFlow, Domain
     HistoryEntry historyEntry =
         ofy().load().type(HistoryEntry.class).ancestor(reloadResourceByForeignKey()).first().now();
     assertThat(ofy().load().entity(token).now().getRedemptionHistoryEntry())
-        .hasValue(DomainHistoryVKey.create(Key.create(historyEntry)));
+        .hasValue(HistoryEntry.createVKey(Key.create(historyEntry)));
   }
 
   @Test
@@ -1275,7 +1274,7 @@ class DomainCreateFlowTest extends ResourceFlowTestCase<DomainCreateFlow, Domain
     assertThat(reloadedToken.isRedeemed()).isTrue();
     assertThat(reloadedToken.getRedemptionHistoryEntry())
         .hasValue(
-            DomainHistoryVKey.create(
+            HistoryEntry.createVKey(
                 Key.create(getHistoryEntries(reloadResourceByForeignKey()).get(0))));
   }
 

core/src/test/java/google/registry/flows/domain/token/AllocationTokenFlowUtilsTest.java

@@ -49,7 +49,6 @@ import google.registry.model.domain.token.AllocationToken;
 import google.registry.model.domain.token.AllocationToken.TokenStatus;
 import google.registry.model.registry.Registry;
 import google.registry.model.reporting.HistoryEntry;
-import google.registry.persistence.DomainHistoryVKey;
 import google.registry.testing.AppEngineExtension;
 import org.joda.time.DateTime;
 import org.junit.jupiter.api.BeforeEach;
@@ -198,7 +197,7 @@ class AllocationTokenFlowUtilsTest {
         new AllocationToken.Builder()
             .setToken("tokeN")
             .setTokenType(SINGLE_USE)
-            .setRedemptionHistoryEntry(DomainHistoryVKey.create(historyEntryKey))
+            .setRedemptionHistoryEntry(HistoryEntry.createVKey(historyEntryKey))
             .build());
     assertThat(
             flowUtils

core/src/test/java/google/registry/model/EntityTestCase.java

@@ -28,6 +28,7 @@ import com.googlecode.objectify.annotation.Parent;
 import com.googlecode.objectify.annotation.Serialize;
 import com.googlecode.objectify.cmd.Query;
 import google.registry.model.ofy.Ofy;
+import google.registry.persistence.EppHistoryVKey;
 import google.registry.persistence.VKey;
 import google.registry.testing.AppEngineExtension;
 import google.registry.testing.FakeClock;
@@ -173,7 +174,8 @@ public abstract class EntityTestCase {
           }
           // Descend into persisted ImmutableObject classes, but not anything else.
           if (ImmutableObject.class.isAssignableFrom(fieldClass)
-              && !VKey.class.isAssignableFrom(fieldClass)) {
+              && !VKey.class.isAssignableFrom(fieldClass)
+              && !EppHistoryVKey.class.isAssignableFrom(fieldClass)) {
             getAllPotentiallyIndexedFieldPaths(fieldClass).stream()
                 .map(subfield -> field.getName() + "." + subfield)
                 .distinct()

core/src/test/java/google/registry/model/domain/DomainBaseSqlTest.java

@@ -633,14 +633,13 @@ public class DomainBaseSqlTest {
                           "4-COM",
                           END_OF_TIME,
                           "registrar1",
-                          createLegacyVKey(
+                          oneTimeBillingEvent.createVKey()),
-                              BillingEvent.OneTime.class, oneTimeBillingEvent.getId())),
                       GracePeriod.createForRecurring(
                           GracePeriodStatus.AUTO_RENEW,
                           "4-COM",
                           END_OF_TIME,
                           "registrar1",
-                          createLegacyVKey(BillingEvent.Recurring.class, billEvent.getId())));
+                          billEvent.createVKey()));
 
               jpaTm().insert(contact);
               jpaTm().insert(contact2);

core/src/test/java/google/registry/model/domain/DomainBaseTest.java

@@ -875,16 +875,13 @@ public class DomainBaseTest extends EntityTestCase {
     ImmutableSet<BillEventInfo> historyIds =
         domain.getGracePeriods().stream()
             .map(
-                gp ->
+                gp -> new BillEventInfo(gp.getRecurringBillingEvent(), gp.getOneTimeBillingEvent()))
-                    new BillEventInfo(
-                        gp.getRecurringBillingEvent(), gp.billingEventRecurringHistoryId,
-                        gp.getOneTimeBillingEvent(), gp.billingEventOneTimeHistoryId))
             .collect(toImmutableSet());
     assertThat(historyIds)
         .isEqualTo(
             ImmutableSet.of(
-                new BillEventInfo(null, null, oneTimeBillKey, historyEntryKey.getId()),
+                new BillEventInfo(null, oneTimeBillKey),
-                new BillEventInfo(recurringBillKey, historyEntryKey.getId(), null, null)));
+                new BillEventInfo(recurringBillKey, null)));
   }
 
   static class BillEventInfo extends ImmutableObject {
@@ -895,13 +892,9 @@ public class DomainBaseTest extends EntityTestCase {
 
     BillEventInfo(
         VKey<BillingEvent.Recurring> billingEventRecurring,
-        Long billingEventRecurringHistoryId,
+        VKey<BillingEvent.OneTime> billingEventOneTime) {
-        VKey<BillingEvent.OneTime> billingEventOneTime,
-        Long billingEventOneTimeHistoryId) {
       this.billingEventRecurring = billingEventRecurring;
-      this.billingEventRecurringHistoryId = billingEventRecurringHistoryId;
       this.billingEventOneTime = billingEventOneTime;
-      this.billingEventOneTimeHistoryId = billingEventOneTimeHistoryId;
     }
   }
 }

core/src/test/java/google/registry/model/domain/GracePeriodTest.java

@@ -63,11 +63,11 @@ public class GracePeriodTest {
     recurringKey =
         VKey.create(
             Recurring.class,
-            12345,
+            12345L,
             Key.create(
                 Key.create(Key.create(DomainBase.class, "1-TEST"), HistoryEntry.class, 343L),
                 Recurring.class,
-                12345));
+                12345L));
   }
 
   @Test
@@ -80,8 +80,6 @@ public class GracePeriodTest {
     assertThat(gracePeriod.getClientId()).isEqualTo("TheRegistrar");
     assertThat(gracePeriod.getExpirationTime()).isEqualTo(now.plusDays(1));
     assertThat(gracePeriod.hasBillingEvent()).isTrue();
-    assertThat(gracePeriod.billingEventOneTimeHistoryId).isEqualTo(12345L);
-    assertThat(gracePeriod.billingEventRecurringHistoryId).isNull();
   }
 
   @Test
@@ -96,8 +94,6 @@ public class GracePeriodTest {
     assertThat(gracePeriod.getClientId()).isEqualTo("TheRegistrar");
     assertThat(gracePeriod.getExpirationTime()).isEqualTo(now.plusDays(1));
     assertThat(gracePeriod.hasBillingEvent()).isTrue();
-    assertThat(gracePeriod.billingEventOneTimeHistoryId).isNull();
-    assertThat(gracePeriod.billingEventRecurringHistoryId).isEqualTo(343L);
   }
 
   @Test

core/src/test/java/google/registry/model/domain/token/AllocationTokenTest.java

@@ -40,7 +40,6 @@ import google.registry.model.domain.DomainBase;
 import google.registry.model.domain.token.AllocationToken.TokenStatus;
 import google.registry.model.domain.token.AllocationToken.TokenType;
 import google.registry.model.reporting.HistoryEntry;
-import google.registry.persistence.DomainHistoryVKey;
 import google.registry.persistence.VKey;
 import org.joda.time.DateTime;
 import org.junit.jupiter.api.BeforeEach;
@@ -86,7 +85,7 @@ public class AllocationTokenTest extends EntityTestCase {
         persistResource(
             new AllocationToken.Builder()
                 .setToken("abc123Single")
-                .setRedemptionHistoryEntry(DomainHistoryVKey.create(historyEntryKey))
+                .setRedemptionHistoryEntry(HistoryEntry.createVKey(historyEntryKey))
                 .setDomainName("example.foo")
                 .setCreationTimeForTest(DateTime.parse("2010-11-12T05:00:00Z"))
                 .setTokenType(SINGLE_USE)
@@ -125,7 +124,7 @@ public class AllocationTokenTest extends EntityTestCase {
             new AllocationToken.Builder()
                 .setToken("abc123")
                 .setTokenType(SINGLE_USE)
-                .setRedemptionHistoryEntry(DomainHistoryVKey.create(historyEntryKey))
+                .setRedemptionHistoryEntry(HistoryEntry.createVKey(historyEntryKey))
                 .setDomainName("blahdomain.foo")
                 .setCreationTimeForTest(DateTime.parse("2010-11-12T05:00:00Z"))
                 .build()),
@@ -231,7 +230,7 @@ public class AllocationTokenTest extends EntityTestCase {
         new AllocationToken.Builder()
             .setToken("foobar")
             .setTokenType(TokenType.UNLIMITED_USE)
-            .setRedemptionHistoryEntry(DomainHistoryVKey.create(historyEntryKey));
+            .setRedemptionHistoryEntry(HistoryEntry.createVKey(historyEntryKey));
     IllegalArgumentException thrown = assertThrows(IllegalArgumentException.class, builder::build);
     assertThat(thrown)
         .hasMessageThat()

core/src/test/java/google/registry/model/translators/EppHistoryVKeyTranslatorFactoryTest.java

@@ -0,0 +1,36 @@
+// Copyright 2020 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.model.translators;
+
+import static google.registry.model.translators.EppHistoryVKeyTranslatorFactory.kindPathToVKeyClass;
+import static org.junit.jupiter.api.Assertions.fail;
+
+import org.junit.jupiter.api.Test;
+
+/** Unit test for {@link EppHistoryVKeyTranslatorFactory}. */
+class EppHistoryVKeyTranslatorFactoryTest {
+
+  @Test
+  void assertAllVKeyClassesHavingCreateFromOfyKeyMethod() {
+    kindPathToVKeyClass.forEach(
+        (kindPath, vKeyClass) -> {
+          try {
+            vKeyClass.getDeclaredMethod("create", com.googlecode.objectify.Key.class);
+          } catch (NoSuchMethodException e) {
+            fail("Missing static method create(com.googlecode.objectify.Key) on " + vKeyClass, e);
+          }
+        });
+  }
+}

core/src/test/java/google/registry/persistence/BillingVKeyTest.java

@@ -0,0 +1,116 @@
+// Copyright 2020 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.persistence;
+
+import static com.google.common.truth.Truth.assertThat;
+import static google.registry.model.common.EntityGroupRoot.getCrossTldKey;
+import static google.registry.persistence.transaction.TransactionManagerFactory.tm;
+
+import com.googlecode.objectify.Key;
+import com.googlecode.objectify.annotation.Entity;
+import com.googlecode.objectify.annotation.Id;
+import com.googlecode.objectify.annotation.Parent;
+import google.registry.model.ImmutableObject;
+import google.registry.model.billing.BillingEvent;
+import google.registry.model.common.EntityGroupRoot;
+import google.registry.model.domain.DomainBase;
+import google.registry.model.reporting.HistoryEntry;
+import google.registry.persistence.BillingVKey.BillingEventVKey;
+import google.registry.persistence.BillingVKey.BillingRecurrenceVKey;
+import google.registry.schema.replay.EntityTest.EntityForTesting;
+import google.registry.testing.AppEngineExtension;
+import google.registry.testing.DualDatabaseTest;
+import google.registry.testing.TestOfyAndSql;
+import javax.persistence.Transient;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+/** Unit test for {@link BillingVKey}. */
+@DualDatabaseTest
+class BillingVKeyTest {
+  @RegisterExtension
+  final AppEngineExtension appEngine =
+      AppEngineExtension.builder()
+          .withDatastoreAndCloudSql()
+          .withOfyTestEntities(BillingVKeyTestEntity.class)
+          .withJpaUnitTestEntities(BillingVKeyTestEntity.class)
+          .build();
+
+  @TestOfyAndSql
+  void testRestoreSymmetricVKey() {
+    Key<HistoryEntry> domainHistoryKey =
+        Key.create(Key.create(DomainBase.class, "domainRepoId"), HistoryEntry.class, 10L);
+
+    Key<BillingEvent.OneTime> oneTimeOfyKey =
+        Key.create(domainHistoryKey, BillingEvent.OneTime.class, 100L);
+    VKey<BillingEvent.OneTime> oneTimeVKey =
+        VKey.create(BillingEvent.OneTime.class, 100L, oneTimeOfyKey);
+
+    Key<BillingEvent.Recurring> recurringOfyKey =
+        Key.create(domainHistoryKey, BillingEvent.Recurring.class, 200L);
+    VKey<BillingEvent.Recurring> recurringVKey =
+        VKey.create(BillingEvent.Recurring.class, 200L, recurringOfyKey);
+
+    BillingVKeyTestEntity original = new BillingVKeyTestEntity(oneTimeVKey, recurringVKey);
+    tm().transact(() -> tm().insert(original));
+    BillingVKeyTestEntity persisted = tm().transact(() -> tm().load(original.createVKey()));
+
+    assertThat(persisted).isEqualTo(original);
+    assertThat(persisted.getBillingEventVKey()).isEqualTo(oneTimeVKey);
+    assertThat(persisted.getBillingRecurrenceVKey()).isEqualTo(recurringVKey);
+  }
+
+  @TestOfyAndSql
+  void testHandleNullVKeyCorrectly() {
+    BillingVKeyTestEntity original = new BillingVKeyTestEntity(null, null);
+    tm().transact(() -> tm().insert(original));
+    BillingVKeyTestEntity persisted = tm().transact(() -> tm().load(original.createVKey()));
+
+    assertThat(persisted).isEqualTo(original);
+  }
+
+  @EntityForTesting
+  @Entity
+  @javax.persistence.Entity
+  private static class BillingVKeyTestEntity extends ImmutableObject {
+    @Transient @Parent Key<EntityGroupRoot> parent = getCrossTldKey();
+
+    @Id @javax.persistence.Id String id = "id";
+
+    BillingEventVKey billingEventVKey;
+
+    BillingRecurrenceVKey billingRecurrenceVKey;
+
+    BillingVKeyTestEntity() {}
+
+    BillingVKeyTestEntity(
+        VKey<BillingEvent.OneTime> onetime, VKey<BillingEvent.Recurring> recurring) {
+      this.billingEventVKey = BillingEventVKey.create(onetime);
+      this.billingRecurrenceVKey = BillingRecurrenceVKey.create(recurring);
+    }
+
+    VKey<BillingEvent.OneTime> getBillingEventVKey() {
+      return billingEventVKey.createVKey();
+    }
+
+    VKey<BillingEvent.Recurring> getBillingRecurrenceVKey() {
+      return billingRecurrenceVKey.createVKey();
+    }
+
+    VKey<BillingVKeyTestEntity> createVKey() {
+      return VKey.create(
+          BillingVKeyTestEntity.class, id, Key.create(parent, BillingVKeyTestEntity.class, id));
+    }
+  }
+}

core/src/test/java/google/registry/persistence/DomainHistoryVKeyTest.java

@@ -56,12 +56,17 @@ class DomainHistoryVKeyTest {
     TestEntity persisted = tm().transact(() -> tm().load(original.createVKey()));
     assertThat(persisted).isEqualTo(original);
     // Double check that the persisted.domainHistoryVKey is a symmetric VKey
-    assertThat(persisted.domainHistoryVKey.getKind()).isEqualTo(HistoryEntry.class);
+    assertThat(persisted.domainHistoryVKey.createOfyKey())
-    assertThat(persisted.domainHistoryVKey.getOfyKey())
         .isEqualTo(
             Key.create(Key.create(DomainBase.class, "domainRepoId"), HistoryEntry.class, 10L));
-    assertThat(persisted.domainHistoryVKey.getSqlKey())
+    assertThat(persisted.domainHistoryVKey.createSqlKey())
         .isEqualTo(new DomainHistoryId("domainRepoId", 10L));
+    assertThat(persisted.domainHistoryVKey.createVKey())
+        .isEqualTo(
+            VKey.create(
+                HistoryEntry.class,
+                new DomainHistoryId("domainRepoId", 10L),
+                Key.create(Key.create(DomainBase.class, "domainRepoId"), HistoryEntry.class, 10L)));
   }
 
   @TestOfyAndSql
@@ -69,9 +74,12 @@ class DomainHistoryVKeyTest {
     Key<HistoryEntry> ofyKey =
         Key.create(Key.create(DomainBase.class, "domainRepoId"), HistoryEntry.class, 10L);
     DomainHistoryVKey domainHistoryVKey = DomainHistoryVKey.create(ofyKey);
-    assertThat(domainHistoryVKey.getKind()).isEqualTo(HistoryEntry.class);
+    assertThat(domainHistoryVKey.createOfyKey()).isEqualTo(ofyKey);
-    assertThat(domainHistoryVKey.getOfyKey()).isEqualTo(ofyKey);
+    assertThat(domainHistoryVKey.createSqlKey())
-    assertThat(domainHistoryVKey.getSqlKey()).isEqualTo(new DomainHistoryId("domainRepoId", 10L));
+        .isEqualTo(new DomainHistoryId("domainRepoId", 10L));
+    assertThat(domainHistoryVKey.createVKey())
+        .isEqualTo(
+            VKey.create(HistoryEntry.class, new DomainHistoryId("domainRepoId", 10L), ofyKey));
   }
 
   @EntityForTesting

core/src/test/java/google/registry/tools/DeleteAllocationTokensCommandTest.java

@@ -27,7 +27,6 @@ import google.registry.model.domain.DomainBase;
 import google.registry.model.domain.token.AllocationToken;
 import google.registry.model.domain.token.AllocationToken.TokenType;
 import google.registry.model.reporting.HistoryEntry;
-import google.registry.persistence.DomainHistoryVKey;
 import java.util.Collection;
 import javax.annotation.Nullable;
 import org.junit.jupiter.api.BeforeEach;
@@ -173,7 +172,7 @@ class DeleteAllocationTokensCommandTest extends CommandTestCase<DeleteAllocation
       String domainToPersist = domainName != null ? domainName : "example.foo";
       DomainBase domain = persistActiveDomain(domainToPersist);
       Key<HistoryEntry> historyEntryKey = Key.create(Key.create(domain), HistoryEntry.class, 1051L);
-      builder.setRedemptionHistoryEntry(DomainHistoryVKey.create(historyEntryKey));
+      builder.setRedemptionHistoryEntry(HistoryEntry.createVKey(historyEntryKey));
     }
     return persistResource(builder.build());
   }

core/src/test/java/google/registry/tools/GenerateAllocationTokensCommandTest.java

@@ -39,7 +39,8 @@ import com.google.common.collect.Iterables;
 import com.google.common.io.Files;
 import google.registry.model.domain.token.AllocationToken;
 import google.registry.model.domain.token.AllocationToken.TokenStatus;
-import google.registry.persistence.DomainHistoryVKey;
+import google.registry.model.reporting.HistoryEntry;
+import google.registry.persistence.VKey;
 import google.registry.testing.DeterministicStringGenerator;
 import google.registry.testing.DeterministicStringGenerator.Rule;
 import google.registry.testing.FakeClock;
@@ -313,7 +314,7 @@ class GenerateAllocationTokensCommandTest extends CommandTestCase<GenerateAlloca
 
   private AllocationToken createToken(
       String token,
-      @Nullable DomainHistoryVKey redemptionHistoryEntry,
+      @Nullable VKey<? extends HistoryEntry> redemptionHistoryEntry,
       @Nullable String domainName) {
     AllocationToken.Builder builder =
         new AllocationToken.Builder().setToken(token).setTokenType(SINGLE_USE);

core/src/test/java/google/registry/tools/GetAllocationTokenCommandTest.java

@@ -28,7 +28,7 @@ import com.google.common.collect.ImmutableList;
 import com.googlecode.objectify.Key;
 import google.registry.model.domain.DomainBase;
 import google.registry.model.domain.token.AllocationToken;
-import google.registry.persistence.DomainHistoryVKey;
+import google.registry.model.reporting.HistoryEntry;
 import org.joda.time.DateTime;
 import org.junit.jupiter.api.Test;
 
@@ -85,7 +85,7 @@ class GetAllocationTokenCommandTest extends CommandTestCase<GetAllocationTokenCo
                 .setTokenType(SINGLE_USE)
                 .setDomainName("fqqdn.tld")
                 .setRedemptionHistoryEntry(
-                    DomainHistoryVKey.create(Key.create(createHistoryEntryForEppResource(domain))))
+                    HistoryEntry.createVKey(Key.create(createHistoryEntryForEppResource(domain))))
                 .build());
     runCommand("foo");
     assertInStdout(

core/src/test/resources/google/registry/model/schema.txt

@@ -278,8 +278,8 @@ class google.registry.model.domain.DomainHistory {
 }
 class google.registry.model.domain.GracePeriod {
   google.registry.model.domain.rgp.GracePeriodStatus type;
-  google.registry.persistence.VKey<google.registry.model.billing.BillingEvent$OneTime> billingEventOneTime;
+  google.registry.persistence.BillingVKey$BillingEventVKey billingEventOneTime;
-  google.registry.persistence.VKey<google.registry.model.billing.BillingEvent$Recurring> billingEventRecurring;
+  google.registry.persistence.BillingVKey$BillingRecurrenceVKey billingEventRecurring;
   java.lang.Long gracePeriodId;
   java.lang.String clientId;
   org.joda.time.DateTime expirationTime;
@@ -888,10 +888,17 @@ enum google.registry.model.transfer.TransferStatus {
   SERVER_APPROVED;
   SERVER_CANCELLED;
 }
-class google.registry.persistence.DomainHistoryVKey {
+class google.registry.persistence.BillingVKey$BillingEventVKey {
-  com.googlecode.objectify.Key<T> ofyKey;
+  java.lang.Long billingId;
-  java.lang.Class<? extends T> kind;
+  java.lang.Long historyRevisionId;
-  java.lang.Long domainHistoryId;
+  java.lang.String repoId;
-  java.lang.Object sqlKey;
+}
-  java.lang.String domainRepoId;
+class google.registry.persistence.BillingVKey$BillingRecurrenceVKey {
+  java.lang.Long billingId;
+  java.lang.Long historyRevisionId;
+  java.lang.String repoId;
+}
+class google.registry.persistence.DomainHistoryVKey {
+  java.lang.Long historyRevisionId;
+  java.lang.String repoId;
 }

db/src/main/resources/sql/er_diagram/brief_er_diagram.html

@@ -261,11 +261,11 @@ td.section {
     </tr> 
     <tr> 
      <td class="property_name">generated on</td> 
-     <td class="property_value">2020-12-05 00:29:03.934355</td> 
+     <td class="property_value">2020-12-16 16:26:55.279224</td> 
     </tr> 
     <tr>
      <td class="property_name">last flyway file</td>
-     <td id="lastFlywayFile" class="property_value">V81__drop_spec11_fkeys.sql</td>
+     <td id="lastFlywayFile" class="property_value">V82__add_columns_to_restore_symmetric_billing_vkey.sql</td>
     </tr>
    </tbody>
   </table> 
@@ -284,7 +284,7 @@ td.section {
      generated on
     </text> 
     <text text-anchor="start" x="4027.94" y="-10.8" font-family="Helvetica,sans-Serif" font-size="14.00">
-     2020-12-05 00:29:03.934355
+     2020-12-16 16:26:55.279224
     </text> 
     <polygon fill="none" stroke="#888888" points="3940.44,-4 3940.44,-44 4205.44,-44 4205.44,-4 3940.44,-4" /> <!-- allocationtoken_a08ccbef --> 
     <g id="node1" class="node"> 

db/src/main/resources/sql/flyway.txt

@@ -79,3 +79,4 @@ V78__add_history_id_for_redemption_history_entry.sql
 V79__drop_foreign_keys_on_pollmessage.sql
 V80__defer_bill_event_key.sql
 V81__drop_spec11_fkeys.sql
+V82__add_columns_to_restore_symmetric_billing_vkey.sql

db/src/main/resources/sql/flyway/V82__add_columns_to_restore_symmetric_billing_vkey.sql

@@ -0,0 +1,22 @@
+-- Copyright 2020 The Nomulus Authors. All Rights Reserved.
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--     http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+alter table "GracePeriod"
+    add column if not exists "billing_event_domain_repo_id" text;
+alter table "GracePeriod"
+    add column if not exists "billing_recurrence_domain_repo_id" text;
+alter table "GracePeriodHistory"
+    add column if not exists "billing_event_domain_repo_id" text;
+alter table "GracePeriodHistory"
+    add column if not exists "billing_recurrence_domain_repo_id" text;

db/src/main/resources/sql/schema/db-schema.sql.generated

@@ -398,8 +398,10 @@
        grace_period_id int8 not null,
         billing_event_id int8,
         billing_event_history_id int8,
+        billing_event_domain_repo_id text,
         billing_recurrence_id int8,
         billing_recurrence_history_id int8,
+        billing_recurrence_domain_repo_id text,
         registrar_id text not null,
         domain_repo_id text not null,
         expiration_time timestamptz not null,
@@ -411,8 +413,10 @@
        grace_period_history_revision_id int8 not null,
         billing_event_id int8,
         billing_event_history_id int8,
+        billing_event_domain_repo_id text,
         billing_recurrence_id int8,
         billing_recurrence_history_id int8,
+        billing_recurrence_domain_repo_id text,
         registrar_id text not null,
         domain_repo_id text not null,
         expiration_time timestamptz not null,

db/src/main/resources/sql/schema/nomulus.golden.sql

@@ -533,7 +533,9 @@ CREATE TABLE public."GracePeriod" (
     expiration_time timestamp with time zone NOT NULL,
     type text NOT NULL,
     billing_event_history_id bigint,
-    billing_recurrence_history_id bigint
+    billing_recurrence_history_id bigint,
+    billing_event_domain_repo_id text,
+    billing_recurrence_domain_repo_id text
 );
 
 
@@ -552,7 +554,9 @@ CREATE TABLE public."GracePeriodHistory" (
     expiration_time timestamp with time zone NOT NULL,
     type text NOT NULL,
     domain_history_revision_id bigint,
-    grace_period_id bigint NOT NULL
+    grace_period_id bigint NOT NULL,
+    billing_event_domain_repo_id text,
+    billing_recurrence_domain_repo_id text
 );