diff --git a/java/com/google/gerrit/server/query/change/ChangeIndexPredicate.java b/java/com/google/gerrit/server/query/change/ChangeIndexPredicate.java
index 1eb2770..7428e3a 100644
--- a/java/com/google/gerrit/server/query/change/ChangeIndexPredicate.java
+++ b/java/com/google/gerrit/server/query/change/ChangeIndexPredicate.java
@@ -17,9 +17,22 @@
 import com.google.gerrit.index.FieldDef;
 import com.google.gerrit.index.query.IndexPredicate;
 import com.google.gerrit.index.query.Matchable;
+import com.google.gerrit.index.query.Predicate;
 
 public abstract class ChangeIndexPredicate extends IndexPredicate<ChangeData>
     implements Matchable<ChangeData> {
+  /**
+   * Returns an index predicate that matches no changes in the index.
+   *
+   * <p>This predicate should be used in preference to a non-index predicate (such as {@code
+   * Predicate.not(Predicate.any())}), since it can be matched efficiently against the index.
+   *
+   * @return an index predicate matching no changes.
+   */
+  public static Predicate<ChangeData> none() {
+    return ChangeStatusPredicate.NONE;
+  }
+
   protected ChangeIndexPredicate(FieldDef<ChangeData, ?> def, String value) {
     super(def, value);
   }
diff --git a/java/com/google/gerrit/server/query/change/ChangeStatusPredicate.java b/java/com/google/gerrit/server/query/change/ChangeStatusPredicate.java
index 8dc17d3..5a7efb8 100644
--- a/java/com/google/gerrit/server/query/change/ChangeStatusPredicate.java
+++ b/java/com/google/gerrit/server/query/change/ChangeStatusPredicate.java
@@ -41,7 +41,7 @@
  */
 public final class ChangeStatusPredicate extends ChangeIndexPredicate {
   private static final String INVALID_STATUS = "__invalid__";
-  private static final Predicate<ChangeData> NONE = new ChangeStatusPredicate(null);
+  static final Predicate<ChangeData> NONE = new ChangeStatusPredicate(null);
 
   private static final TreeMap<String, Predicate<ChangeData>> PREDICATES;
   private static final Predicate<ChangeData> CLOSED;
diff --git a/java/com/google/gerrit/server/query/change/ConflictsPredicate.java b/java/com/google/gerrit/server/query/change/ConflictsPredicate.java
index 7dc7a0b..20c43af 100644
--- a/java/com/google/gerrit/server/query/change/ConflictsPredicate.java
+++ b/java/com/google/gerrit/server/query/change/ConflictsPredicate.java
@@ -14,6 +14,9 @@
 
 package com.google.gerrit.server.query.change;
 
+import static java.util.concurrent.TimeUnit.MINUTES;
+
+import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.common.data.SubmitTypeRecord;
 import com.google.gerrit.index.query.PostFilterPredicate;
 import com.google.gerrit.index.query.Predicate;
@@ -41,6 +44,8 @@
 import org.eclipse.jgit.revwalk.RevWalk;
 
 public class ConflictsPredicate {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
   // UI code may depend on this string, so use caution when changing.
   protected static final String TOO_MANY_FILES = "too many files to find conflicts";
 
@@ -54,7 +59,12 @@
       cd = args.changeDataFactory.create(args.db.get(), c);
       files = cd.currentFilePaths();
     } catch (IOException e) {
-      throw new OrmException(e);
+      warnWithOccasionalStackTrace(
+          e,
+          "Error constructing conflicts predicates for change %s in %s",
+          c.getId(),
+          c.getProject());
+      return ChangeIndexPredicate.none();
     }
 
     if (3 + files.size() > args.indexConfig.maxTerms()) {
@@ -201,4 +211,13 @@
       return alreadyAccepted;
     }
   }
+
+  private static void warnWithOccasionalStackTrace(Throwable cause, String format, Object... args) {
+    logger.atWarning().logVarargs(format, args);
+    logger
+        .atWarning()
+        .withCause(cause)
+        .atMostEvery(1, MINUTES)
+        .logVarargs("(Re-logging with stack trace) " + format, args);
+  }
 }
diff --git a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
index 8b606a0..60289fb 100644
--- a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
+++ b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.query.change;
 
+import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.TruthJUnit.assume;
 import static com.google.gerrit.extensions.client.ListChangesOption.DETAILED_LABELS;
@@ -73,6 +74,7 @@
 import com.google.gerrit.index.IndexConfig;
 import com.google.gerrit.index.QueryOptions;
 import com.google.gerrit.index.Schema;
+import com.google.gerrit.index.query.Predicate;
 import com.google.gerrit.lifecycle.LifecycleManager;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Account.Id;
@@ -3198,6 +3200,26 @@
     assertQuery("project:repo+foo", change);
   }
 
+  @Test
+  public void none() throws Exception {
+    TestRepository<Repo> repo = createProject("repo");
+    Change change = insert(repo, newChange(repo));
+
+    assertQuery(ChangeIndexPredicate.none());
+
+    for (Predicate<ChangeData> matchingOneChange :
+        ImmutableList.of(
+            // One index query, one post-filtering query.
+            queryBuilder.parse(change.getId().toString()),
+            queryBuilder.parse("ownerin:Administrators"))) {
+      assertQuery(matchingOneChange, change);
+      assertQuery(Predicate.or(ChangeIndexPredicate.none(), matchingOneChange), change);
+      assertQuery(Predicate.and(ChangeIndexPredicate.none(), matchingOneChange));
+      assertQuery(
+          Predicate.and(Predicate.not(ChangeIndexPredicate.none()), matchingOneChange), change);
+    }
+  }
+
   protected ChangeInserter newChange(TestRepository<Repo> repo) throws Exception {
     return newChange(repo, null, null, null, null, false, false);
   }
@@ -3359,21 +3381,32 @@
     List<ChangeInfo> result = query.get();
     Iterable<Change.Id> ids = ids(result);
     assertThat(ids)
-        .named(format(query, ids, changes))
+        .named(format(query.getQuery(), ids, changes))
         .containsExactlyElementsIn(Arrays.asList(changes))
         .inOrder();
     return result;
   }
 
-  private String format(
-      QueryRequest query, Iterable<Change.Id> actualIds, Change.Id... expectedChanges)
+  protected void assertQuery(Predicate<ChangeData> predicate, Change... changes) throws Exception {
+    ImmutableList<Change.Id> actualIds =
+        queryProvider.get().query(predicate).stream()
+            .map(ChangeData::getId)
+            .collect(toImmutableList());
+    Change.Id[] expectedIds = Arrays.stream(changes).map(Change::getId).toArray(Change.Id[]::new);
+    assertThat(actualIds)
+        .named(format(predicate.toString(), actualIds, expectedIds))
+        .containsExactlyElementsIn(expectedIds)
+        .inOrder();
+  }
+
+  private String format(String query, Iterable<Change.Id> actualIds, Change.Id... expectedChanges)
       throws RestApiException {
-    StringBuilder b = new StringBuilder();
-    b.append("query '").append(query.getQuery()).append("' with expected changes ");
-    b.append(format(Arrays.asList(expectedChanges)));
-    b.append(" and result ");
-    b.append(format(actualIds));
-    return b.toString();
+    return "query '"
+        + query
+        + "' with expected changes "
+        + format(Arrays.asList(expectedChanges))
+        + " and result "
+        + format(actualIds);
   }
 
   private String format(Iterable<Change.Id> changeIds) throws RestApiException {