diff --git a/java/com/google/gerrit/server/PatchSetUtil.java b/java/com/google/gerrit/server/PatchSetUtil.java
index 252eb61..c9ca972 100644
--- a/java/com/google/gerrit/server/PatchSetUtil.java
+++ b/java/com/google/gerrit/server/PatchSetUtil.java
@@ -214,14 +214,13 @@
     return false;
   }
 
-  /** Returns the full commit message for the given project at the given patchset revision */
-  public String getFullCommitMessage(Project.NameKey project, PatchSet patchSet)
-      throws IOException {
+  /** Returns the commit for the given project at the given patchset revision */
+  public RevCommit getRevCommit(Project.NameKey project, PatchSet patchSet) throws IOException {
     try (Repository repo = repoManager.openRepository(project);
         RevWalk rw = new RevWalk(repo)) {
       RevCommit src = rw.parseCommit(ObjectId.fromString(patchSet.getRevision().get()));
       rw.parseBody(src);
-      return src.getFullMessage();
+      return src;
     }
   }
 }
diff --git a/java/com/google/gerrit/server/account/Emails.java b/java/com/google/gerrit/server/account/Emails.java
index 8a48167..e91ce49 100644
--- a/java/com/google/gerrit/server/account/Emails.java
+++ b/java/com/google/gerrit/server/account/Emails.java
@@ -95,6 +95,16 @@
     return builder.build();
   }
 
+  /**
+   * Returns the accounts with the given email.
+   *
+   * <p>This method behaves just like {@link #getAccountFor(String)}, except that accounts are not
+   * looked up by their preferred email. Thus, this method does not rely on the accounts index.
+   */
+  public ImmutableSet<Account.Id> getAccountForExternal(String email) throws IOException {
+    return externalIds.byEmail(email).stream().map(ExternalId::accountId).collect(toImmutableSet());
+  }
+
   private <T> T executeIndexQuery(Action<T> action) throws OrmException {
     try {
       return retryHelper.execute(ActionType.INDEX_QUERY, action, OrmException.class::isInstance);
diff --git a/java/com/google/gerrit/server/rules/PrologEnvironment.java b/java/com/google/gerrit/server/rules/PrologEnvironment.java
index 083898b..412e0f9 100644
--- a/java/com/google/gerrit/server/rules/PrologEnvironment.java
+++ b/java/com/google/gerrit/server/rules/PrologEnvironment.java
@@ -18,6 +18,7 @@
 import com.google.gerrit.server.AnonymousUser;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.PatchSetUtil;
+import com.google.gerrit.server.account.Emails;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.patch.PatchListCache;
@@ -176,6 +177,7 @@
     private final int reductionLimit;
     private final int compileLimit;
     private final PatchSetUtil patchsetUtil;
+    private Emails emails;
 
     @Inject
     Args(
@@ -187,7 +189,8 @@
         IdentifiedUser.GenericFactory userFactory,
         Provider<AnonymousUser> anonymousUser,
         @GerritServerConfig Config config,
-        PatchSetUtil patchsetUtil) {
+        PatchSetUtil patchsetUtil,
+        Emails emails) {
       this.projectCache = projectCache;
       this.permissionBackend = permissionBackend;
       this.repositoryManager = repositoryManager;
@@ -196,6 +199,7 @@
       this.userFactory = userFactory;
       this.anonymousUser = anonymousUser;
       this.patchsetUtil = patchsetUtil;
+      this.emails = emails;
 
       int limit = config.getInt("rules", null, "reductionLimit", 100000);
       reductionLimit = limit <= 0 ? Integer.MAX_VALUE : limit;
@@ -247,5 +251,9 @@
     public PatchSetUtil getPatchsetUtil() {
       return patchsetUtil;
     }
+
+    public Emails getEmails() {
+      return emails;
+    }
   }
 }
diff --git a/java/com/google/gerrit/server/rules/StoredValues.java b/java/com/google/gerrit/server/rules/StoredValues.java
index 6770732..8b9cfe3 100644
--- a/java/com/google/gerrit/server/rules/StoredValues.java
+++ b/java/com/google/gerrit/server/rules/StoredValues.java
@@ -20,7 +20,6 @@
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.PatchSet;
-import com.google.gerrit.reviewdb.client.PatchSetInfo;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.AnonymousUser;
@@ -34,8 +33,6 @@
 import com.google.gerrit.server.patch.PatchListCache;
 import com.google.gerrit.server.patch.PatchListKey;
 import com.google.gerrit.server.patch.PatchListNotAvailableException;
-import com.google.gerrit.server.patch.PatchSetInfoFactory;
-import com.google.gerrit.server.patch.PatchSetInfoNotAvailableException;
 import com.google.gerrit.server.permissions.PermissionBackend;
 import com.google.gerrit.server.project.ProjectState;
 import com.google.gerrit.server.query.change.ChangeData;
@@ -47,6 +44,7 @@
 import java.util.Map;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevCommit;
 
 public final class StoredValues {
   public static final StoredValue<Accounts> ACCOUNTS = create(Accounts.class);
@@ -74,32 +72,16 @@
     }
   }
 
-  public static final StoredValue<PatchSetInfo> PATCH_SET_INFO =
-      new StoredValue<PatchSetInfo>() {
+  public static final StoredValue<RevCommit> COMMIT =
+      new StoredValue<RevCommit>() {
         @Override
-        public PatchSetInfo createValue(Prolog engine) {
-          Change change = getChange(engine);
-          PatchSet ps = getPatchSet(engine);
-          PrologEnvironment env = (PrologEnvironment) engine.control;
-          PatchSetInfoFactory patchInfoFactory = env.getArgs().getPatchSetInfoFactory();
-          try {
-            return patchInfoFactory.get(change.getProject(), ps);
-          } catch (PatchSetInfoNotAvailableException e) {
-            throw new SystemException(e.getMessage());
-          }
-        }
-      };
-
-  public static final StoredValue<String> COMMIT_MESSAGE =
-      new StoredValue<String>() {
-        @Override
-        public String createValue(Prolog engine) {
+        public RevCommit createValue(Prolog engine) {
           Change change = getChange(engine);
           PatchSet ps = getPatchSet(engine);
           PrologEnvironment env = (PrologEnvironment) engine.control;
           PatchSetUtil patchSetUtil = env.getArgs().getPatchsetUtil();
           try {
-            return patchSetUtil.getFullCommitMessage(change.getProject(), ps);
+            return patchSetUtil.getRevCommit(change.getProject(), ps);
           } catch (IOException e) {
             throw new SystemException(e.getMessage());
           }
diff --git a/java/gerrit/AbstractCommitUserIdentityPredicate.java b/java/gerrit/AbstractCommitUserIdentityPredicate.java
index c2aaa76..1bfc95c 100644
--- a/java/gerrit/AbstractCommitUserIdentityPredicate.java
+++ b/java/gerrit/AbstractCommitUserIdentityPredicate.java
@@ -14,9 +14,12 @@
 
 package gerrit;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.reviewdb.client.Account;
-import com.google.gerrit.reviewdb.client.UserIdentity;
+import com.google.gerrit.server.account.Emails;
+import com.google.gerrit.server.rules.PrologEnvironment;
 import com.googlecode.prolog_cafe.exceptions.PrologException;
+import com.googlecode.prolog_cafe.exceptions.SystemException;
 import com.googlecode.prolog_cafe.lang.IntegerTerm;
 import com.googlecode.prolog_cafe.lang.Operation;
 import com.googlecode.prolog_cafe.lang.Predicate;
@@ -24,6 +27,8 @@
 import com.googlecode.prolog_cafe.lang.StructureTerm;
 import com.googlecode.prolog_cafe.lang.SymbolTerm;
 import com.googlecode.prolog_cafe.lang.Term;
+import java.io.IOException;
+import org.eclipse.jgit.lib.PersonIdent;
 
 abstract class AbstractCommitUserIdentityPredicate extends Predicate.P3 {
   private static final SymbolTerm user = SymbolTerm.intern("user", 1);
@@ -36,7 +41,7 @@
     cont = n;
   }
 
-  protected Operation exec(Prolog engine, UserIdentity userId) throws PrologException {
+  protected Operation exec(Prolog engine, PersonIdent userId) throws PrologException {
     engine.setB0();
     Term a1 = arg1.dereference();
     Term a2 = arg2.dereference();
@@ -46,7 +51,18 @@
     Term nameTerm = Prolog.Nil;
     Term emailTerm = Prolog.Nil;
 
-    Account.Id id = userId.getAccount();
+    PrologEnvironment env = (PrologEnvironment) engine.control;
+    Emails emails = env.getArgs().getEmails();
+    Account.Id id = null;
+    try {
+      ImmutableSet<Account.Id> ids = emails.getAccountForExternal(userId.getEmailAddress());
+      if (ids.size() == 1) {
+        id = ids.iterator().next();
+      }
+    } catch (IOException e) {
+      throw new SystemException(e.getMessage());
+    }
+
     if (id == null) {
       idTerm = anonymous;
     } else {
@@ -58,7 +74,7 @@
       nameTerm = SymbolTerm.create(name);
     }
 
-    String email = userId.getEmail();
+    String email = userId.getEmailAddress();
     if (email != null && !email.equals("")) {
       emailTerm = SymbolTerm.create(email);
     }
diff --git a/java/gerrit/BUILD b/java/gerrit/BUILD
index 4644af87..8281d8e 100644
--- a/java/gerrit/BUILD
+++ b/java/gerrit/BUILD
@@ -11,5 +11,6 @@
         "//lib/flogger:api",
         "//lib/jgit/org.eclipse.jgit:jgit",
         "//lib/prolog:runtime",
+        "@guava//jar",
     ],
 )
diff --git a/java/gerrit/PRED_commit_author_3.java b/java/gerrit/PRED_commit_author_3.java
index a876b5e..998b30e 100644
--- a/java/gerrit/PRED_commit_author_3.java
+++ b/java/gerrit/PRED_commit_author_3.java
@@ -14,13 +14,12 @@
 
 package gerrit;
 
-import com.google.gerrit.reviewdb.client.PatchSetInfo;
-import com.google.gerrit.reviewdb.client.UserIdentity;
 import com.google.gerrit.server.rules.StoredValues;
 import com.googlecode.prolog_cafe.exceptions.PrologException;
 import com.googlecode.prolog_cafe.lang.Operation;
 import com.googlecode.prolog_cafe.lang.Prolog;
 import com.googlecode.prolog_cafe.lang.Term;
+import org.eclipse.jgit.revwalk.RevCommit;
 
 public class PRED_commit_author_3 extends AbstractCommitUserIdentityPredicate {
   public PRED_commit_author_3(Term a1, Term a2, Term a3, Operation n) {
@@ -29,8 +28,7 @@
 
   @Override
   public Operation exec(Prolog engine) throws PrologException {
-    PatchSetInfo psInfo = StoredValues.PATCH_SET_INFO.get(engine);
-    UserIdentity author = psInfo.getAuthor();
-    return exec(engine, author);
+    RevCommit revCommit = StoredValues.COMMIT.get(engine);
+    return exec(engine, revCommit.getAuthorIdent());
   }
 }
diff --git a/java/gerrit/PRED_commit_committer_3.java b/java/gerrit/PRED_commit_committer_3.java
index b24b004..293d8ce 100644
--- a/java/gerrit/PRED_commit_committer_3.java
+++ b/java/gerrit/PRED_commit_committer_3.java
@@ -14,13 +14,12 @@
 
 package gerrit;
 
-import com.google.gerrit.reviewdb.client.PatchSetInfo;
-import com.google.gerrit.reviewdb.client.UserIdentity;
 import com.google.gerrit.server.rules.StoredValues;
 import com.googlecode.prolog_cafe.exceptions.PrologException;
 import com.googlecode.prolog_cafe.lang.Operation;
 import com.googlecode.prolog_cafe.lang.Prolog;
 import com.googlecode.prolog_cafe.lang.Term;
+import org.eclipse.jgit.revwalk.RevCommit;
 
 public class PRED_commit_committer_3 extends AbstractCommitUserIdentityPredicate {
   public PRED_commit_committer_3(Term a1, Term a2, Term a3, Operation n) {
@@ -29,8 +28,7 @@
 
   @Override
   public Operation exec(Prolog engine) throws PrologException {
-    PatchSetInfo psInfo = StoredValues.PATCH_SET_INFO.get(engine);
-    UserIdentity committer = psInfo.getCommitter();
-    return exec(engine, committer);
+    RevCommit revCommit = StoredValues.COMMIT.get(engine);
+    return exec(engine, revCommit.getCommitterIdent());
   }
 }
diff --git a/java/gerrit/PRED_commit_message_1.java b/java/gerrit/PRED_commit_message_1.java
index 05bb4bb..eb996d6 100644
--- a/java/gerrit/PRED_commit_message_1.java
+++ b/java/gerrit/PRED_commit_message_1.java
@@ -21,6 +21,7 @@
 import com.googlecode.prolog_cafe.lang.Prolog;
 import com.googlecode.prolog_cafe.lang.SymbolTerm;
 import com.googlecode.prolog_cafe.lang.Term;
+import org.eclipse.jgit.revwalk.RevCommit;
 
 /**
  * Returns the commit message as a symbol
@@ -40,7 +41,8 @@
     engine.setB0();
     Term a1 = arg1.dereference();
 
-    String commitMessage = StoredValues.COMMIT_MESSAGE.get(engine);
+    RevCommit revCommit = StoredValues.COMMIT.get(engine);
+    String commitMessage = revCommit.getFullMessage();
 
     SymbolTerm msg = SymbolTerm.create(commitMessage);
     if (!a1.unify(msg, engine.trail)) {
diff --git a/javatests/com/google/gerrit/acceptance/server/rules/RulesIT.java b/javatests/com/google/gerrit/acceptance/server/rules/RulesIT.java
index bf01a21..98dca3e 100644
--- a/javatests/com/google/gerrit/acceptance/server/rules/RulesIT.java
+++ b/javatests/com/google/gerrit/acceptance/server/rules/RulesIT.java
@@ -71,21 +71,17 @@
 
   @Test
   public void testUserPredicate() throws Exception {
-    // This test results in a RULE_ERROR as Prolog tries to find accounts by email, using the index.
-    // TODO(maximeg) get OK results
     modifySubmitRules(
         String.format(
             "gerrit:commit_author(user(%d), '%s', '%s')",
             user.getId().get(), user.fullName, user.email));
-    assertThat(statusForRule()).isEqualTo(SubmitRecord.Status.RULE_ERROR);
+    assertThat(statusForRule()).isEqualTo(SubmitRecord.Status.OK);
   }
 
   @Test
   public void testCommitAuthorPredicate() throws Exception {
-    // This test results in a RULE_ERROR as Prolog tries to find accounts by email, using the index.
-    // TODO(maximeg) get OK results
     modifySubmitRules("gerrit:commit_author(Id)");
-    assertThat(statusForRule()).isEqualTo(SubmitRecord.Status.RULE_ERROR);
+    assertThat(statusForRule()).isEqualTo(SubmitRecord.Status.OK);
   }
 
   private SubmitRecord.Status statusForRule() throws Exception {
diff --git a/javatests/com/google/gerrit/server/rules/GerritCommonTest.java b/javatests/com/google/gerrit/server/rules/GerritCommonTest.java
index 314941e..086dd65 100644
--- a/javatests/com/google/gerrit/server/rules/GerritCommonTest.java
+++ b/javatests/com/google/gerrit/server/rules/GerritCommonTest.java
@@ -49,7 +49,7 @@
             bind(PrologEnvironment.Args.class)
                 .toInstance(
                     new PrologEnvironment.Args(
-                        null, null, null, null, null, null, null, cfg, null));
+                        null, null, null, null, null, null, null, cfg, null, null));
           }
         });
   }