diff --git a/Documentation/user-search.txt b/Documentation/user-search.txt
index abd2531..5d7a78b 100644
--- a/Documentation/user-search.txt
+++ b/Documentation/user-search.txt
@@ -276,6 +276,8 @@
 ones using a bracket expression). For example, to match all XML
 files named like 'name1.xml', 'name2.xml', and 'name3.xml' use
 `file:"^name[1-3].xml"`.
++
+Slash ('/') is used path separator.
 
 [[file]]
 file:'NAME', f:'NAME'::
@@ -294,8 +296,40 @@
 +
 Matches any change touching a file with extension 'EXT', case-insensitive. The
 extension is defined as the portion of the filename following the final `.`.
-Files with no `.` in their name have no extension and cannot be matched with
-this operator; use `file:` instead.
+Files with no `.` in their name have no extension and can be matched by an
+empty string.
+
+[[onlyextensions]]
+onlyextensions:'EXT_LIST', onlyexts:'EXT_LIST'::
++
+Matches any change touching only files with extensions that are listed in
+'EXT_LIST' (comma-separated list). The matching is done case-insensitive.
+An extension is defined as the portion of the filename following the final `.`.
+Files with no `.` in their name have no extension and can be matched by an
+empty string.
+
+[[directory]]
+directory:'DIR', dir:'DIR'::
++
+Matches any change where the current patch set touches a file in the directory
+'DIR'. The matching is done case-insensitive. 'DIR' can be a full directory
+name, a directory prefix or any combination of intermediate directory segments.
+E.g. a change that touches a file in the directory 'a/b/c' matches for 'a/b/c',
+'a', 'a/b', 'b', 'b/c' and 'c'.
++
+Slash ('/') is used path separator. Leading and trailing slashes are allowed
+but are not mandatory.
++
+If 'DIR' starts with `^` it matches directories and directory segments by
+regular expression. The link:http://www.brics.dk/automaton/[dk.brics.automaton
+library] is used for evaluation of such patterns.
+
+[[footer]]
+footer:'FOOTER'::
++
+Matches any change that has 'FOOTER' as footer in the commit message of the
+current patch set. 'FOOTER' can be specified verbatim ('<key>: <value>', must
+be quoted) or as '<key>=<value>'. The matching is done case-insensitive.
 
 [[star]]
 star:'LABEL'::
diff --git a/java/com/google/gerrit/server/index/change/ChangeField.java b/java/com/google/gerrit/server/index/change/ChangeField.java
index 52dac9d..593fb85 100644
--- a/java/com/google/gerrit/server/index/change/ChangeField.java
+++ b/java/com/google/gerrit/server/index/change/ChangeField.java
@@ -24,6 +24,7 @@
 import static com.google.gerrit.index.FieldDef.storedOnly;
 import static com.google.gerrit.index.FieldDef.timestamp;
 import static java.nio.charset.StandardCharsets.UTF_8;
+import static java.util.stream.Collectors.joining;
 import static java.util.stream.Collectors.toList;
 import static java.util.stream.Collectors.toSet;
 
@@ -191,6 +192,29 @@
       exact(ChangeQueryBuilder.FIELD_EXTENSION).buildRepeatable(ChangeField::getExtensions);
 
   public static Set<String> getExtensions(ChangeData cd) throws OrmException {
+    return extensions(cd).collect(toSet());
+  }
+
+  /**
+   * File extensions of each file modified in the current patch set as a sorted list. The purpose of
+   * this field is to allow matching changes that only touch files with certain file extensions.
+   */
+  public static final FieldDef<ChangeData, String> ONLY_EXTENSIONS =
+      exact(ChangeQueryBuilder.FIELD_ONLY_EXTENSIONS).build(ChangeField::getAllExtensionsAsList);
+
+  public static String getAllExtensionsAsList(ChangeData cd) throws OrmException {
+    return extensions(cd).distinct().sorted().collect(joining(","));
+  }
+
+  /**
+   * Returns a stream with all file extensions that are used by files in the given change. A file
+   * extension is defined as the portion of the filename following the final `.`. Files with no `.`
+   * in their name have no extension. For them an empty string is returned as part of the stream.
+   *
+   * <p>If the change contains multiple files with the same extension the extension is returned
+   * multiple times in the stream (once per file).
+   */
+  private static Stream<String> extensions(ChangeData cd) throws OrmException {
     try {
       return cd.currentFilePaths()
           .stream()
@@ -198,14 +222,69 @@
           // If we want to find "all Java files", we want to match both .java and .JAVA, even if we
           // normally care about case sensitivity. (Whether we should change the existing file/path
           // predicates to be case insensitive is a separate question.)
-          .map(f -> Files.getFileExtension(f).toLowerCase(Locale.US))
-          .filter(e -> !e.isEmpty())
+          .map(f -> Files.getFileExtension(f).toLowerCase(Locale.US));
+    } catch (IOException e) {
+      throw new OrmException(e);
+    }
+  }
+
+  /** Footers from the commit message of the current patch set. */
+  public static final FieldDef<ChangeData, Iterable<String>> FOOTER =
+      exact(ChangeQueryBuilder.FIELD_FOOTER).buildRepeatable(ChangeField::getFooters);
+
+  public static Set<String> getFooters(ChangeData cd) throws OrmException {
+    try {
+      return cd.commitFooters()
+          .stream()
+          .map(f -> f.toString().toLowerCase(Locale.US))
           .collect(toSet());
     } catch (IOException e) {
       throw new OrmException(e);
     }
   }
 
+  /** Folders that are touched by the current patch set. */
+  public static final FieldDef<ChangeData, Iterable<String>> DIRECTORY =
+      exact(ChangeQueryBuilder.FIELD_DIRECTORY).buildRepeatable(ChangeField::getDirectories);
+
+  public static Set<String> getDirectories(ChangeData cd) throws OrmException {
+    List<String> paths;
+    try {
+      paths = cd.currentFilePaths();
+    } catch (IOException e) {
+      throw new OrmException(e);
+    }
+
+    Splitter s = Splitter.on('/').omitEmptyStrings();
+    Set<String> r = new HashSet<>();
+    for (String path : paths) {
+      StringBuilder directory = new StringBuilder();
+      directory.append("");
+      r.add(directory.toString());
+      String nextPart = null;
+      for (String part : s.split(path)) {
+        if (nextPart != null) {
+          r.add(nextPart);
+
+          if (directory.length() > 0) {
+            directory.append("/");
+          }
+          directory.append(nextPart);
+
+          String intermediateDir = directory.toString();
+          int i = intermediateDir.indexOf('/');
+          while (i >= 0) {
+            r.add(intermediateDir);
+            intermediateDir = intermediateDir.substring(i + 1);
+            i = intermediateDir.indexOf('/');
+          }
+        }
+        nextPart = part;
+      }
+    }
+    return r;
+  }
+
   /** Owner/creator of the change. */
   public static final FieldDef<ChangeData, Integer> OWNER =
       integer(ChangeQueryBuilder.FIELD_OWNER).build(changeGetter(c -> c.getOwner().get()));
diff --git a/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java b/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java
index cd24c92..cde6a64 100644
--- a/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java
+++ b/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java
@@ -103,7 +103,16 @@
 
   @Deprecated static final Schema<ChangeData> V51 = schema(V50, ChangeField.TOTAL_COMMENT_COUNT);
 
-  static final Schema<ChangeData> V52 = schema(V51, ChangeField.EXTENSION);
+  @Deprecated static final Schema<ChangeData> V52 = schema(V51, ChangeField.EXTENSION);
+
+  @Deprecated static final Schema<ChangeData> V53 = schema(V52, ChangeField.ONLY_EXTENSIONS);
+
+  @Deprecated static final Schema<ChangeData> V54 = schema(V53, ChangeField.FOOTER);
+
+  @Deprecated static final Schema<ChangeData> V55 = schema(V54, ChangeField.DIRECTORY);
+
+  // The computation of the 'extension' field is changed, hence reindexing is required.
+  static final Schema<ChangeData> V56 = schema(V55);
 
   public static final String NAME = "changes";
   public static final ChangeSchemaDefinitions INSTANCE = new ChangeSchemaDefinitions();
diff --git a/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java b/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
index 0b889dc..b62a1d7 100644
--- a/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
+++ b/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
@@ -138,8 +138,11 @@
   public static final String FIELD_COMMENTBY = "commentby";
   public static final String FIELD_COMMIT = "commit";
   public static final String FIELD_COMMITTER = "committer";
+  public static final String FIELD_DIRECTORY = "directory";
   public static final String FIELD_EXACTCOMMITTER = "exactcommitter";
   public static final String FIELD_EXTENSION = "extension";
+  public static final String FIELD_ONLY_EXTENSIONS = "onlyextensions";
+  public static final String FIELD_FOOTER = "footer";
   public static final String FIELD_CONFLICTS = "conflicts";
   public static final String FIELD_DELETED = "deleted";
   public static final String FIELD_DELTA = "delta";
@@ -749,6 +752,45 @@
   }
 
   @Operator
+  public Predicate<ChangeData> onlyexts(String extList) throws QueryParseException {
+    return onlyextensions(extList);
+  }
+
+  @Operator
+  public Predicate<ChangeData> onlyextensions(String extList) throws QueryParseException {
+    if (args.getSchema().hasField(ChangeField.ONLY_EXTENSIONS)) {
+      return new FileExtensionListPredicate(extList);
+    }
+    throw new QueryParseException(
+        "'onlyextensions' operator is not supported by change index version");
+  }
+
+  @Operator
+  public Predicate<ChangeData> footer(String footer) throws QueryParseException {
+    if (args.getSchema().hasField(ChangeField.FOOTER)) {
+      return new FooterPredicate(footer);
+    }
+    throw new QueryParseException("'footer' operator is not supported by change index version");
+  }
+
+  @Operator
+  public Predicate<ChangeData> dir(String directory) throws QueryParseException {
+    return directory(directory);
+  }
+
+  @Operator
+  public Predicate<ChangeData> directory(String directory) throws QueryParseException {
+    if (args.getSchema().hasField(ChangeField.DIRECTORY)) {
+      if (directory.startsWith("^")) {
+        return new RegexDirectoryPredicate(directory);
+      }
+
+      return new DirectoryPredicate(directory);
+    }
+    throw new QueryParseException("'directory' operator is not supported by change index version");
+  }
+
+  @Operator
   public Predicate<ChangeData> label(String name)
       throws QueryParseException, OrmException, IOException, ConfigInvalidException {
     Set<Account.Id> accounts = null;
diff --git a/java/com/google/gerrit/server/query/change/DirectoryPredicate.java b/java/com/google/gerrit/server/query/change/DirectoryPredicate.java
new file mode 100644
index 0000000..676a208
--- /dev/null
+++ b/java/com/google/gerrit/server/query/change/DirectoryPredicate.java
@@ -0,0 +1,40 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// 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 com.google.gerrit.server.query.change;
+
+import com.google.common.base.CharMatcher;
+import com.google.gerrit.server.index.change.ChangeField;
+import com.google.gwtorm.server.OrmException;
+import java.util.Locale;
+
+public class DirectoryPredicate extends ChangeIndexPredicate {
+  private static String clean(String directory) {
+    return CharMatcher.is('/').trimFrom(directory).toLowerCase(Locale.US);
+  }
+
+  DirectoryPredicate(String value) {
+    super(ChangeField.DIRECTORY, clean(value));
+  }
+
+  @Override
+  public boolean match(ChangeData cd) throws OrmException {
+    return ChangeField.getDirectories(cd).contains(value);
+  }
+
+  @Override
+  public int getCost() {
+    return 0;
+  }
+}
diff --git a/java/com/google/gerrit/server/query/change/FileExtensionListPredicate.java b/java/com/google/gerrit/server/query/change/FileExtensionListPredicate.java
new file mode 100644
index 0000000..3399338
--- /dev/null
+++ b/java/com/google/gerrit/server/query/change/FileExtensionListPredicate.java
@@ -0,0 +1,47 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// 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 com.google.gerrit.server.query.change;
+
+import static java.util.stream.Collectors.joining;
+
+import com.google.common.base.Splitter;
+import com.google.gerrit.server.index.change.ChangeField;
+import com.google.gwtorm.server.OrmException;
+
+public class FileExtensionListPredicate extends ChangeIndexPredicate {
+  private static String clean(String extList) {
+    return Splitter.on(',')
+        .splitToList(extList)
+        .stream()
+        .map(FileExtensionPredicate::clean)
+        .distinct()
+        .sorted()
+        .collect(joining(","));
+  }
+
+  FileExtensionListPredicate(String value) {
+    super(ChangeField.ONLY_EXTENSIONS, clean(value));
+  }
+
+  @Override
+  public boolean match(ChangeData cd) throws OrmException {
+    return ChangeField.getAllExtensionsAsList(cd).equals(value);
+  }
+
+  @Override
+  public int getCost() {
+    return 0;
+  }
+}
diff --git a/java/com/google/gerrit/server/query/change/FileExtensionPredicate.java b/java/com/google/gerrit/server/query/change/FileExtensionPredicate.java
index ee5030a..5353f11 100644
--- a/java/com/google/gerrit/server/query/change/FileExtensionPredicate.java
+++ b/java/com/google/gerrit/server/query/change/FileExtensionPredicate.java
@@ -19,7 +19,7 @@
 import java.util.Locale;
 
 public class FileExtensionPredicate extends ChangeIndexPredicate {
-  private static String clean(String ext) {
+  static String clean(String ext) {
     if (ext.startsWith(".")) {
       ext = ext.substring(1);
     }
diff --git a/java/com/google/gerrit/server/query/change/FooterPredicate.java b/java/com/google/gerrit/server/query/change/FooterPredicate.java
new file mode 100644
index 0000000..1d7d19b
--- /dev/null
+++ b/java/com/google/gerrit/server/query/change/FooterPredicate.java
@@ -0,0 +1,46 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// 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 com.google.gerrit.server.query.change;
+
+import com.google.gerrit.server.index.change.ChangeField;
+import com.google.gwtorm.server.OrmException;
+import java.util.Locale;
+
+public class FooterPredicate extends ChangeIndexPredicate {
+  private static String clean(String value) {
+    int indexEquals = value.indexOf('=');
+    int indexColon = value.indexOf(':');
+
+    // footer key cannot contain '='
+    if (indexEquals > 0 && (indexEquals < indexColon || indexColon < 0)) {
+      value = value.substring(0, indexEquals) + ": " + value.substring(indexEquals + 1);
+    }
+    return value.toLowerCase(Locale.US);
+  }
+
+  FooterPredicate(String value) {
+    super(ChangeField.FOOTER, clean(value));
+  }
+
+  @Override
+  public boolean match(ChangeData cd) throws OrmException {
+    return ChangeField.getFooters(cd).contains(value);
+  }
+
+  @Override
+  public int getCost() {
+    return 0;
+  }
+}
diff --git a/java/com/google/gerrit/server/query/change/RegexDirectoryPredicate.java b/java/com/google/gerrit/server/query/change/RegexDirectoryPredicate.java
new file mode 100644
index 0000000..1d49f1e
--- /dev/null
+++ b/java/com/google/gerrit/server/query/change/RegexDirectoryPredicate.java
@@ -0,0 +1,48 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// 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 com.google.gerrit.server.query.change;
+
+import com.google.gerrit.server.index.change.ChangeField;
+import com.google.gwtorm.server.OrmException;
+import dk.brics.automaton.RegExp;
+import dk.brics.automaton.RunAutomaton;
+
+public class RegexDirectoryPredicate extends ChangeRegexPredicate {
+  protected final RunAutomaton pattern;
+
+  public RegexDirectoryPredicate(String re) {
+    super(ChangeField.DIRECTORY, re);
+
+    if (re.startsWith("^")) {
+      re = re.substring(1);
+    }
+
+    if (re.endsWith("$") && !re.endsWith("\\$")) {
+      re = re.substring(0, re.length() - 1);
+    }
+
+    this.pattern = new RunAutomaton(new RegExp(re).toAutomaton());
+  }
+
+  @Override
+  public boolean match(ChangeData cd) throws OrmException {
+    return ChangeField.getDirectories(cd).stream().anyMatch(pattern::run);
+  }
+
+  @Override
+  public int getCost() {
+    return 1;
+  }
+}
diff --git a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
index 79eae2a..7872a82 100644
--- a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
+++ b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
@@ -1379,7 +1379,7 @@
     Change change1 = insert(repo, newChangeWithFiles(repo, "foo.h", "foo.cc"));
     Change change2 = insert(repo, newChangeWithFiles(repo, "bar.H", "bar.CC"));
     Change change3 = insert(repo, newChangeWithFiles(repo, "dir/baz.h", "dir/baz.cc"));
-    Change change4 = insert(repo, newChangeWithFiles(repo, "Quux.java"));
+    Change change4 = insert(repo, newChangeWithFiles(repo, "Quux.java", "foo"));
 
     assertQuery("extension:java", change4);
     assertQuery("ext:java", change4);
@@ -1387,6 +1387,205 @@
     assertQuery("ext:jAvA", change4);
     assertQuery("ext:.jAvA", change4);
     assertQuery("ext:cc", change3, change2, change1);
+
+    if (getSchemaVersion() >= 56) {
+      // matching changes with files that have no extension is possible
+      assertQuery("ext:\"\"", change4);
+      assertFailingQuery("ext:");
+    }
+  }
+
+  @Test
+  public void byOnlyExtensions() throws Exception {
+    if (getSchemaVersion() < 53) {
+      assertMissingField(ChangeField.ONLY_EXTENSIONS);
+      String unsupportedOperatorMessage =
+          "'onlyextensions' operator is not supported by change index version";
+      assertFailingQuery("onlyextensions:txt,jpg", unsupportedOperatorMessage);
+      assertFailingQuery("onlyexts:txt,jpg", unsupportedOperatorMessage);
+      return;
+    }
+
+    TestRepository<Repo> repo = createProject("repo");
+    Change change1 = insert(repo, newChangeWithFiles(repo, "foo.h", "foo.cc", "bar.cc"));
+    Change change2 = insert(repo, newChangeWithFiles(repo, "bar.H", "bar.CC", "foo.H"));
+    Change change3 = insert(repo, newChangeWithFiles(repo, "foo.CC", "bar.cc"));
+    Change change4 = insert(repo, newChangeWithFiles(repo, "dir/baz.h", "dir/baz.cc"));
+    Change change5 = insert(repo, newChangeWithFiles(repo, "Quux.java"));
+    Change change6 = insert(repo, newChangeWithFiles(repo, "foo.txt", "foo"));
+    Change change7 = insert(repo, newChangeWithFiles(repo, "foo"));
+
+    // case doesn't matter
+    assertQuery("onlyextensions:cc,h", change4, change2, change1);
+    assertQuery("onlyextensions:CC,H", change4, change2, change1);
+    assertQuery("onlyextensions:cc,H", change4, change2, change1);
+    assertQuery("onlyextensions:cC,h", change4, change2, change1);
+    assertQuery("onlyextensions:cc", change3);
+    assertQuery("onlyextensions:CC", change3);
+    assertQuery("onlyexts:java", change5);
+    assertQuery("onlyexts:jAvA", change5);
+    assertQuery("onlyexts:.jAvA", change5);
+
+    // order doesn't matter
+    assertQuery("onlyextensions:h,cc", change4, change2, change1);
+    assertQuery("onlyextensions:H,CC", change4, change2, change1);
+
+    // specifying extension with '.' is okay
+    assertQuery("onlyextensions:.cc,.h", change4, change2, change1);
+    assertQuery("onlyextensions:cc,.h", change4, change2, change1);
+    assertQuery("onlyextensions:.cc,h", change4, change2, change1);
+    assertQuery("onlyexts:.java", change5);
+
+    // matching changes without extension is possible
+    assertQuery("onlyexts:txt");
+    assertQuery("onlyexts:txt,", change6);
+    assertQuery("onlyexts:,txt", change6);
+    assertQuery("onlyextensions:\"\"", change7);
+    assertQuery("onlyexts:\"\"", change7);
+    assertQuery("onlyextensions:,", change7);
+    assertQuery("onlyexts:,", change7);
+    assertFailingQuery("onlyextensions:");
+    assertFailingQuery("onlyexts:");
+
+    // inverse queries
+    assertQuery("-onlyextensions:cc,h", change7, change6, change5, change3);
+  }
+
+  @Test
+  public void byFooter() throws Exception {
+    if (getSchemaVersion() < 54) {
+      assertMissingField(ChangeField.FOOTER);
+      assertFailingQuery(
+          "footer:Change-Id=I3d2b978ed455f835d1dad2daa920be0b0ec2ae36",
+          "'footer' operator is not supported by change index version");
+      return;
+    }
+
+    TestRepository<Repo> repo = createProject("repo");
+    RevCommit commit1 = repo.parseBody(repo.commit().message("Test\n\nfoo: bar").create());
+    Change change1 = insert(repo, newChangeForCommit(repo, commit1));
+    RevCommit commit2 = repo.parseBody(repo.commit().message("Test\n\nfoo: baz").create());
+    Change change2 = insert(repo, newChangeForCommit(repo, commit2));
+    RevCommit commit3 = repo.parseBody(repo.commit().message("Test\n\nfoo: bar\nfoo:baz").create());
+    Change change3 = insert(repo, newChangeForCommit(repo, commit3));
+    RevCommit commit4 = repo.parseBody(repo.commit().message("Test\n\nfoo: bar=baz").create());
+    Change change4 = insert(repo, newChangeForCommit(repo, commit4));
+
+    // create a changes with lines that look like footers, but which are not
+    RevCommit commit5 =
+        repo.parseBody(
+            repo.commit().message("Test\n\nfoo: bar\n\nfoo=bar").insertChangeId().create());
+    Change change5 = insert(repo, newChangeForCommit(repo, commit5));
+    RevCommit commit6 = repo.parseBody(repo.commit().message("Test\n\na=b: c").create());
+    insert(repo, newChangeForCommit(repo, commit6));
+
+    // matching by 'key=value' works
+    assertQuery("footer:foo=bar", change3, change1);
+    assertQuery("footer:foo=baz", change3, change2);
+    assertQuery("footer:Change-Id=" + change5.getKey(), change5);
+    assertQuery("footer:foo=bar=baz", change4);
+
+    // case doesn't matter
+    assertQuery("footer:foo=BAR", change3, change1);
+    assertQuery("footer:FOO=bar", change3, change1);
+    assertQuery("footer:fOo=BaZ", change3, change2);
+
+    // verbatim matching of footers works
+    assertQuery("footer:\"foo: bar\"", change3, change1);
+    assertQuery("footer:\"foo: baz\"", change3, change2);
+    assertQuery("footer:\"Change-Id: " + change5.getKey() + "\"", change5);
+    assertQuery("footer:\"foo: bar=baz\"", change4);
+
+    // expect no match because 'a=b: c' of commit6 is not a valid footer (footer key cannot contain
+    // '=')
+    assertQuery("footer:a=b=c");
+    assertQuery("footer:\"a=b: c\"");
+
+    // expect empty result for invalid footers
+    assertQuery("footer:foo");
+    assertQuery("footer:foo=");
+    assertQuery("footer:=foo");
+    assertQuery("footer:=");
+  }
+
+  @Test
+  public void byDirectory() throws Exception {
+    if (getSchemaVersion() < 55) {
+      assertMissingField(ChangeField.DIRECTORY);
+      String unsupportedOperatorMessage =
+          "'directory' operator is not supported by change index version";
+      assertFailingQuery("directory:src/java", unsupportedOperatorMessage);
+      assertFailingQuery("dir:src/java", unsupportedOperatorMessage);
+      return;
+    }
+
+    TestRepository<Repo> repo = createProject("repo");
+    Change change1 = insert(repo, newChangeWithFiles(repo, "src/foo.h", "src/foo.cc"));
+    Change change2 = insert(repo, newChangeWithFiles(repo, "src/java/foo.java", "src/js/bar.js"));
+    Change change3 =
+        insert(repo, newChangeWithFiles(repo, "documentation/training/slides/README.txt"));
+    Change change4 = insert(repo, newChangeWithFiles(repo, "a.txt"));
+    Change change5 = insert(repo, newChangeWithFiles(repo, "a/b/c/d/e/foo.txt"));
+
+    // matching by directory prefix works
+    assertQuery("directory:src", change2, change1);
+    assertQuery("directory:src/java", change2);
+    assertQuery("directory:src/js", change2);
+    assertQuery("directory:documentation/", change3);
+    assertQuery("directory:documentation/training", change3);
+    assertQuery("directory:documentation/training/slides", change3);
+
+    // 'dir' alias works
+    assertQuery("dir:src", change2, change1);
+    assertQuery("dir:src/java", change2);
+
+    // case doesn't matter
+    assertQuery("directory:Documentation/TrAiNiNg/SLIDES", change3);
+
+    // leading and trailing '/' doesn't matter
+    assertQuery("directory:/documentation/training/slides", change3);
+    assertQuery("directory:documentation/training/slides/", change3);
+    assertQuery("directory:/documentation/training/slides/", change3);
+
+    // files do not match as directory
+    assertQuery("directory:src/foo.h");
+    assertQuery("directory:documentation/training/slides/README.txt");
+
+    // root directory matches all changes
+    assertQuery("directory:/", change5, change4, change3, change2, change1);
+    assertQuery("directory:\"\"", change5, change4, change3, change2, change1);
+    assertFailingQuery("directory:");
+
+    // matching single directory segments works
+    assertQuery("directory:java", change2);
+    assertQuery("directory:slides", change3);
+
+    // files do not match as directory segment
+    assertQuery("directory:foo.h");
+
+    // matching any combination of intermediate directory segments works
+    assertQuery("directory:training/slides", change3);
+    assertQuery("directory:b/c", change5);
+    assertQuery("directory:b/c/d", change5);
+    assertQuery("directory:b/c/d/e", change5);
+    assertQuery("directory:c/d", change5);
+    assertQuery("directory:c/d/e", change5);
+    assertQuery("directory:d/e", change5);
+
+    // files do not match as directory segments
+    assertQuery("directory:d/e/foo.txt");
+    assertQuery("directory:e/foo.txt");
+
+    // matching any combination of intermediate directory segments works with leading and trailing
+    // '/'
+    assertQuery("directory:/b/c", change5);
+    assertQuery("directory:/b/c/", change5);
+    assertQuery("directory:b/c/", change5);
+
+    // match by regexp
+    assertQuery("directory:^.*va.*", change2);
+    assertQuery("directory:^documentation/.*/slides", change3);
+    assertQuery("directory:^train.*", change3);
   }
 
   @Test
@@ -3126,12 +3325,19 @@
         .isFalse();
   }
 
-  protected void assertFailingQuery(String query, String expectedMessage) throws Exception {
+  protected void assertFailingQuery(String query) throws Exception {
+    assertFailingQuery(query, null);
+  }
+
+  protected void assertFailingQuery(String query, @Nullable String expectedMessage)
+      throws Exception {
     try {
       assertQuery(query);
       fail("expected BadRequestException for query '" + query + "'");
     } catch (BadRequestException e) {
-      assertThat(e.getMessage()).isEqualTo(expectedMessage);
+      if (expectedMessage != null) {
+        assertThat(e.getMessage()).isEqualTo(expectedMessage);
+      }
     }
   }
 
diff --git a/polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.js b/polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.js
index 8aff87e..6699bd1 100644
--- a/polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.js
+++ b/polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.js
@@ -36,9 +36,12 @@
     'conflicts:',
     'deleted:',
     'delta:',
+    'dir:',
+    'directory:',
     'ext:',
     'extension:',
     'file:',
+    'footer:',
     'from:',
     'has:',
     'has:draft',
@@ -66,6 +69,8 @@
     'is:wip',
     'label:',
     'message:',
+    'onlyexts:',
+    'onlyextensions:',
     'owner:',
     'ownerin:',
     'parentproject:',