diff --git a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/CollectionReference.java b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/CollectionReference.java
index f6d472a2aeb2..a1cf52ba10de 100644
--- a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/CollectionReference.java
+++ b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/CollectionReference.java
@@ -59,7 +59,7 @@ public class CollectionReference extends Query {
    */
   @Nonnull
   public String getId() {
-    return path.getId();
+    return options.getCollectionId();
   }
 
   /**
@@ -69,7 +69,7 @@ public String getId() {
    */
   @Nullable
   public DocumentReference getParent() {
-    ResourcePath parent = path.getParent();
+    ResourcePath parent = options.getParentPath();
     return parent.isDocument() ? new DocumentReference(firestore, parent) : null;
   }
 
@@ -81,7 +81,7 @@ public DocumentReference getParent() {
    */
   @Nonnull
   public String getPath() {
-    return path.getPath();
+    return getResourcePath().getPath();
   }
 
   /**
@@ -104,10 +104,10 @@ public DocumentReference document() {
    */
   @Nonnull
   public DocumentReference document(@Nonnull String childPath) {
-    ResourcePath documentPath = path.append(childPath);
+    ResourcePath documentPath = getResourcePath().append(childPath);
     Preconditions.checkArgument(
         documentPath.isDocument(),
-        String.format("Path should point to a Document Reference: %s", path));
+        String.format("Path should point to a Document Reference: %s", getPath()));
     return new DocumentReference(firestore, documentPath);
   }
 
@@ -124,8 +124,8 @@ public DocumentReference document(@Nonnull String childPath) {
   @Nonnull
   public Iterable<DocumentReference> listDocuments() {
     ListDocumentsRequest.Builder request = ListDocumentsRequest.newBuilder();
-    request.setParent(path.getParent().toString());
-    request.setCollectionId(this.getId());
+    request.setParent(options.getParentPath().toString());
+    request.setCollectionId(options.getCollectionId());
     request.setMask(DocumentMask.getDefaultInstance());
     request.setShowMissing(true);
 
@@ -206,4 +206,9 @@ public ApiFuture<DocumentReference> add(Object pojo) {
     }
     return add((Map<String, Object>) converted);
   }
+
+  /** Returns a resource path pointing to this collection. */
+  ResourcePath getResourcePath() {
+    return options.getParentPath().append(options.getCollectionId());
+  }
 }
diff --git a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Firestore.java b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Firestore.java
index 6476c91ba0cd..32d223f99a4d 100644
--- a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Firestore.java
+++ b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Firestore.java
@@ -62,6 +62,16 @@ public interface Firestore extends Service<FirestoreOptions>, AutoCloseable {
   @Nonnull
   Iterable<CollectionReference> getCollections();
 
+  /**
+   * Creates and returns a new @link{Query} that includes all documents in the database that are
+   * contained in a collection or subcollection with the given @code{collectionId}.
+   *
+   * @param collectionId Identifies the collections to query over. Every collection or subcollection
+   *     with this ID as the last segment of its path will be included. Cannot contain a slash.
+   * @return The created Query.
+   */
+  Query collectionGroup(@Nonnull String collectionId);
+
   /**
    * Executes the given updateFunction and then attempts to commit the changes applied within the
    * transaction. If any document read within the transaction has changed, the updateFunction will
diff --git a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/FirestoreImpl.java b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/FirestoreImpl.java
index 3a1c677aaccc..6e568748a870 100644
--- a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/FirestoreImpl.java
+++ b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/FirestoreImpl.java
@@ -106,7 +106,10 @@ public WriteBatch batch() {
   @Nonnull
   @Override
   public CollectionReference collection(@Nonnull String collectionPath) {
-    return new CollectionReference(this, databasePath.append(collectionPath));
+    ResourcePath path = databasePath.append(collectionPath);
+    Preconditions.checkArgument(
+        path.isCollection(), "Invalid path specified. Path should point to a collection");
+    return new CollectionReference(this, path);
   }
 
   @Nonnull
@@ -244,6 +247,16 @@ public void onCompleted() {
     return futureList;
   }
 
+  @Nonnull
+  @Override
+  public Query collectionGroup(@Nonnull final String collectionId) {
+    Preconditions.checkArgument(
+        !collectionId.contains("/"),
+        String.format(
+            "Invalid collectionId '%s'. Collection IDs must not contain '/'.", collectionId));
+    return new Query(this, collectionId);
+  }
+
   @Nonnull
   @Override
   public <T> ApiFuture<T> runTransaction(@Nonnull final Transaction.Function<T> updateFunction) {
@@ -401,6 +414,11 @@ String getDatabaseName() {
     return databasePath.getDatabaseName().toString();
   }
 
+  /** Returns a path to the Firestore project associated with this client. */
+  ResourcePath getResourcePath() {
+    return databasePath;
+  }
+
   /** Returns the underlying RPC client. */
   FirestoreRpc getClient() {
     return firestoreClient;
diff --git a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Query.java b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Query.java
index 739f57e14883..20912a52d3e3 100644
--- a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Query.java
+++ b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Query.java
@@ -26,14 +26,18 @@
 import com.google.api.core.ApiFuture;
 import com.google.api.core.SettableApiFuture;
 import com.google.api.gax.rpc.ApiStreamObserver;
+import com.google.auto.value.AutoValue;
 import com.google.cloud.Timestamp;
+import com.google.cloud.firestore.Query.QueryOptions.Builder;
 import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.firestore.v1.Cursor;
 import com.google.firestore.v1.Document;
 import com.google.firestore.v1.RunQueryRequest;
 import com.google.firestore.v1.RunQueryResponse;
 import com.google.firestore.v1.StructuredQuery;
+import com.google.firestore.v1.StructuredQuery.CollectionSelector;
 import com.google.firestore.v1.StructuredQuery.CompositeFilter;
 import com.google.firestore.v1.StructuredQuery.FieldReference;
 import com.google.firestore.v1.StructuredQuery.Filter;
@@ -58,7 +62,6 @@
  */
 public class Query {
 
-  final ResourcePath path;
   final FirestoreImpl firestore;
   final QueryOptions options;
 
@@ -78,7 +81,7 @@ StructuredQuery.Direction getDirection() {
     }
   }
 
-  private abstract static class FieldFilter {
+  abstract static class FieldFilter {
     final FieldPath fieldPath;
     final Object value;
 
@@ -160,7 +163,7 @@ Filter toProto() {
     }
   }
 
-  private static class FieldOrder {
+  static final class FieldOrder {
     final FieldPath fieldPath;
     final Direction direction;
 
@@ -178,92 +181,91 @@ Order toProto() {
   }
 
   /** Options that define a Firestore Query. */
-  private static class QueryOptions {
-
-    private int limit;
-    private int offset;
-    private Cursor startCursor;
-    private Cursor endCursor;
-    private List<FieldFilter> fieldFilters;
-    private List<FieldOrder> fieldOrders;
-    private List<FieldReference> fieldProjections;
-
-    QueryOptions() {
-      limit = -1;
-      offset = -1;
-      fieldFilters = new ArrayList<>();
-      fieldOrders = new ArrayList<>();
-      fieldProjections = new ArrayList<>();
-    }
+  @AutoValue
+  abstract static class QueryOptions {
 
-    QueryOptions(QueryOptions options) {
-      limit = options.limit;
-      offset = options.offset;
-      startCursor = options.startCursor;
-      endCursor = options.endCursor;
-      fieldFilters = new ArrayList<>(options.fieldFilters);
-      fieldOrders = new ArrayList<>(options.fieldOrders);
-      fieldProjections = options.fieldProjections;
-    }
+    abstract ResourcePath getParentPath();
 
-    @Override
-    public boolean equals(Object o) {
-      if (this == o) {
-        return true;
-      }
-      if (o == null || getClass() != o.getClass()) {
-        return false;
-      }
+    abstract String getCollectionId();
 
-      QueryOptions that = (QueryOptions) o;
+    abstract boolean getAllDescendants();
 
-      if (limit != that.limit) {
-        return false;
-      }
-      if (offset != that.offset) {
-        return false;
-      }
-      if (startCursor != null ? !startCursor.equals(that.startCursor) : that.startCursor != null) {
-        return false;
-      }
-      if (endCursor != null ? !endCursor.equals(that.endCursor) : that.endCursor != null) {
-        return false;
-      }
-      if (!fieldFilters.equals(that.fieldFilters)) {
-        return false;
-      }
-      if (!fieldOrders.equals(that.fieldOrders)) {
-        return false;
-      }
-      return fieldProjections.equals(that.fieldProjections);
+    abstract @Nullable Integer getLimit();
+
+    abstract @Nullable Integer getOffset();
+
+    abstract @Nullable Cursor getStartCursor();
+
+    abstract @Nullable Cursor getEndCursor();
+
+    abstract ImmutableList<FieldFilter> getFieldFilters();
+
+    abstract ImmutableList<FieldOrder> getFieldOrders();
+
+    abstract ImmutableList<FieldReference> getFieldProjections();
+
+    static Builder builder() {
+      return new AutoValue_Query_QueryOptions.Builder()
+          .setAllDescendants(false)
+          .setFieldOrders(ImmutableList.<FieldOrder>of())
+          .setFieldFilters(ImmutableList.<FieldFilter>of())
+          .setFieldProjections(ImmutableList.<FieldReference>of());
     }
 
-    @Override
-    public int hashCode() {
-      int result = limit;
-      result = 31 * result + offset;
-      result = 31 * result + (startCursor != null ? startCursor.hashCode() : 0);
-      result = 31 * result + (endCursor != null ? endCursor.hashCode() : 0);
-      result = 31 * result + fieldFilters.hashCode();
-      result = 31 * result + fieldOrders.hashCode();
-      result = 31 * result + fieldProjections.hashCode();
-      return result;
+    abstract Builder toBuilder();
+
+    @AutoValue.Builder
+    abstract static class Builder {
+      abstract Builder setParentPath(ResourcePath value);
+
+      abstract Builder setCollectionId(String value);
+
+      abstract Builder setAllDescendants(boolean value);
+
+      abstract Builder setLimit(Integer value);
+
+      abstract Builder setOffset(Integer value);
+
+      abstract Builder setStartCursor(@Nullable Cursor value);
+
+      abstract Builder setEndCursor(@Nullable Cursor value);
+
+      abstract Builder setFieldFilters(ImmutableList<FieldFilter> value);
+
+      abstract Builder setFieldOrders(ImmutableList<FieldOrder> value);
+
+      abstract Builder setFieldProjections(ImmutableList<FieldReference> value);
+
+      abstract QueryOptions build();
     }
   }
 
+  /** Creates a query for documents in a single collection */
   Query(FirestoreImpl firestore, ResourcePath path) {
-    this(firestore, path, new QueryOptions());
+    this(
+        firestore,
+        QueryOptions.builder()
+            .setParentPath(path.getParent())
+            .setCollectionId(path.getId())
+            .build());
   }
 
-  protected Query(
-      FirestoreImpl firestore,
-      ResourcePath path,
-      QueryOptions queryOptions) { // Elevated access level for mocking.
-    Preconditions.checkArgument(
-        path.isCollection(), "Invalid path specified. Path should point to a collection");
+  /**
+   * Creates a Collection Group query that matches all documents directly nested under a
+   * specifically named collection
+   */
+  Query(FirestoreImpl firestore, String collectionId) {
+    this(
+        firestore,
+        QueryOptions.builder()
+            .setParentPath(firestore.getResourcePath())
+            .setCollectionId(collectionId)
+            .setAllDescendants(true)
+            .build());
+  }
 
+  private Query(FirestoreImpl firestore, QueryOptions queryOptions) {
     this.firestore = firestore;
-    this.path = path;
     this.options = queryOptions;
   }
 
@@ -283,20 +285,20 @@ private static boolean isUnaryComparison(@Nullable Object value) {
   }
 
   /** Computes the backend ordering semantics for DocumentSnapshot cursors. */
-  private List<FieldOrder> createImplicitOrderBy() {
-    List<FieldOrder> implicitOrders = new ArrayList<>(options.fieldOrders);
+  private ImmutableList<FieldOrder> createImplicitOrderBy() {
+    List<FieldOrder> implicitOrders = new ArrayList<>(options.getFieldOrders());
     boolean hasDocumentId = false;
 
     if (implicitOrders.isEmpty()) {
       // If no explicit ordering is specified, use the first inequality to define an implicit order.
-      for (FieldFilter fieldFilter : options.fieldFilters) {
+      for (FieldFilter fieldFilter : options.getFieldFilters()) {
         if (!fieldFilter.isEqualsFilter()) {
           implicitOrders.add(new FieldOrder(fieldFilter.fieldPath, Direction.ASCENDING));
           break;
         }
       }
     } else {
-      for (FieldOrder fieldOrder : options.fieldOrders) {
+      for (FieldOrder fieldOrder : options.getFieldOrders()) {
         if (fieldOrder.fieldPath.equals(FieldPath.DOCUMENT_ID)) {
           hasDocumentId = true;
         }
@@ -312,11 +314,12 @@ private List<FieldOrder> createImplicitOrderBy() {
 
       implicitOrders.add(new FieldOrder(FieldPath.documentId(), lastDirection));
     }
-    return implicitOrders;
+
+    return ImmutableList.<FieldOrder>builder().addAll(implicitOrders).build();
   }
 
   private Cursor createCursor(
-      List<FieldOrder> order, DocumentSnapshot documentSnapshot, boolean before) {
+      ImmutableList<FieldOrder> order, DocumentSnapshot documentSnapshot, boolean before) {
     List<Object> fieldValues = new ArrayList<>();
 
     for (FieldOrder fieldOrder : order) {
@@ -378,9 +381,14 @@ private Cursor createCursor(List<FieldOrder> order, Object[] fieldValues, boolea
    * a DocumentReference that can directly be used in the Query.
    */
   private Object convertReference(Object fieldValue) {
+    ResourcePath basePath =
+        options.getAllDescendants()
+            ? options.getParentPath()
+            : options.getParentPath().append(options.getCollectionId());
+
     DocumentReference reference;
     if (fieldValue instanceof String) {
-      reference = new DocumentReference(firestore, path.append((String) fieldValue));
+      reference = new DocumentReference(firestore, basePath.append((String) fieldValue));
     } else if (fieldValue instanceof DocumentReference) {
       reference = (DocumentReference) fieldValue;
     } else {
@@ -389,13 +397,14 @@ private Object convertReference(Object fieldValue) {
               + "DocumentReference.");
     }
 
-    if (!this.path.isPrefixOf(reference.getResourcePath())) {
+    if (!basePath.isPrefixOf(reference.getResourcePath())) {
       throw new IllegalArgumentException(
           String.format(
               "'%s' is not part of the query result set and cannot be used as a query boundary.",
               reference.getPath()));
     }
-    if (!reference.getParent().getResourcePath().equals(this.path)) {
+
+    if (!options.getAllDescendants() && !reference.getParent().getResourcePath().equals(basePath)) {
       throw new IllegalArgumentException(
           String.format(
               "Only a direct child can be used as a query boundary. Found: '%s'",
@@ -429,21 +438,18 @@ public Query whereEqualTo(@Nonnull String field, @Nullable Object value) {
   @Nonnull
   public Query whereEqualTo(@Nonnull FieldPath fieldPath, @Nullable Object value) {
     Preconditions.checkState(
-        options.startCursor == null && options.endCursor == null,
+        options.getStartCursor() == null && options.getEndCursor() == null,
         "Cannot call whereEqualTo() after defining a boundary with startAt(), "
             + "startAfter(), endBefore() or endAt().");
-    QueryOptions newOptions = new QueryOptions(options);
 
     if (isUnaryComparison(value)) {
-      newOptions.fieldFilters.add(new UnaryFilter(fieldPath, value));
+      Builder newOptions = options.toBuilder();
+      UnaryFilter newFieldFilter = new UnaryFilter(fieldPath, value);
+      newOptions.setFieldFilters(append(options.getFieldFilters(), newFieldFilter));
+      return new Query(firestore, newOptions.build());
     } else {
-      if (fieldPath.equals(FieldPath.DOCUMENT_ID)) {
-        value = this.convertReference(value);
-      }
-      newOptions.fieldFilters.add(new ComparisonFilter(fieldPath, EQUAL, value));
+      return whereHelper(fieldPath, EQUAL, value);
     }
-
-    return new Query(firestore, path, newOptions);
   }
 
   /**
@@ -470,12 +476,10 @@ public Query whereLessThan(@Nonnull String field, @Nonnull Object value) {
   @Nonnull
   public Query whereLessThan(@Nonnull FieldPath fieldPath, @Nonnull Object value) {
     Preconditions.checkState(
-        options.startCursor == null && options.endCursor == null,
+        options.getStartCursor() == null && options.getEndCursor() == null,
         "Cannot call whereLessThan() after defining a boundary with startAt(), "
             + "startAfter(), endBefore() or endAt().");
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldFilters.add(new ComparisonFilter(fieldPath, LESS_THAN, value));
-    return new Query(firestore, path, newOptions);
+    return whereHelper(fieldPath, LESS_THAN, value);
   }
 
   /**
@@ -502,12 +506,10 @@ public Query whereLessThanOrEqualTo(@Nonnull String field, @Nonnull Object value
   @Nonnull
   public Query whereLessThanOrEqualTo(@Nonnull FieldPath fieldPath, @Nonnull Object value) {
     Preconditions.checkState(
-        options.startCursor == null && options.endCursor == null,
+        options.getStartCursor() == null && options.getEndCursor() == null,
         "Cannot call whereLessThanOrEqualTo() after defining a boundary with startAt(), "
             + "startAfter(), endBefore() or endAt().");
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldFilters.add(new ComparisonFilter(fieldPath, LESS_THAN_OR_EQUAL, value));
-    return new Query(firestore, path, newOptions);
+    return whereHelper(fieldPath, LESS_THAN_OR_EQUAL, value);
   }
 
   /**
@@ -534,12 +536,10 @@ public Query whereGreaterThan(@Nonnull String field, @Nonnull Object value) {
   @Nonnull
   public Query whereGreaterThan(@Nonnull FieldPath fieldPath, @Nonnull Object value) {
     Preconditions.checkState(
-        options.startCursor == null && options.endCursor == null,
+        options.getStartCursor() == null && options.getEndCursor() == null,
         "Cannot call whereGreaterThan() after defining a boundary with startAt(), "
             + "startAfter(), endBefore() or endAt().");
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldFilters.add(new ComparisonFilter(fieldPath, GREATER_THAN, value));
-    return new Query(firestore, path, newOptions);
+    return whereHelper(fieldPath, GREATER_THAN, value);
   }
 
   /**
@@ -566,12 +566,10 @@ public Query whereGreaterThanOrEqualTo(@Nonnull String field, @Nonnull Object va
   @Nonnull
   public Query whereGreaterThanOrEqualTo(@Nonnull FieldPath fieldPath, @Nonnull Object value) {
     Preconditions.checkState(
-        options.startCursor == null && options.endCursor == null,
+        options.getStartCursor() == null && options.getEndCursor() == null,
         "Cannot call whereGreaterThanOrEqualTo() after defining a boundary with startAt(), "
             + "startAfter(), endBefore() or endAt().");
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldFilters.add(new ComparisonFilter(fieldPath, GREATER_THAN_OR_EQUAL, value));
-    return new Query(firestore, path, newOptions);
+    return whereHelper(fieldPath, GREATER_THAN_OR_EQUAL, value);
   }
 
   /**
@@ -604,12 +602,22 @@ public Query whereArrayContains(@Nonnull String field, @Nonnull Object value) {
   @Nonnull
   public Query whereArrayContains(@Nonnull FieldPath fieldPath, @Nonnull Object value) {
     Preconditions.checkState(
-        options.startCursor == null && options.endCursor == null,
+        options.getStartCursor() == null && options.getEndCursor() == null,
         "Cannot call whereArrayContains() after defining a boundary with startAt(), "
             + "startAfter(), endBefore() or endAt().");
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldFilters.add(new ComparisonFilter(fieldPath, ARRAY_CONTAINS, value));
-    return new Query(firestore, path, newOptions);
+    return whereHelper(fieldPath, ARRAY_CONTAINS, value);
+  }
+
+  private Query whereHelper(
+      FieldPath fieldPath, StructuredQuery.FieldFilter.Operator operator, Object value) {
+    if (fieldPath.equals(FieldPath.DOCUMENT_ID)) {
+      value = this.convertReference(value);
+    }
+
+    Builder newOptions = options.toBuilder();
+    ComparisonFilter newFieldFilter = new ComparisonFilter(fieldPath, operator, value);
+    newOptions.setFieldFilters(append(options.getFieldFilters(), newFieldFilter));
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -658,14 +666,15 @@ public Query orderBy(@Nonnull String field, @Nonnull Direction direction) {
   @Nonnull
   public Query orderBy(@Nonnull FieldPath fieldPath, @Nonnull Direction direction) {
     Preconditions.checkState(
-        options.startCursor == null && options.endCursor == null,
+        options.getStartCursor() == null && options.getEndCursor() == null,
         "Cannot specify an orderBy() constraint after calling startAt(), "
             + "startAfter(), endBefore() or endAt().");
 
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldOrders.add(new FieldOrder(fieldPath, direction));
+    Builder newOptions = options.toBuilder();
+    FieldOrder newFieldOrder = new FieldOrder(fieldPath, direction);
+    newOptions.setFieldOrders(append(options.getFieldOrders(), newFieldOrder));
 
-    return new Query(firestore, path, newOptions);
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -677,9 +686,7 @@ public Query orderBy(@Nonnull FieldPath fieldPath, @Nonnull Direction direction)
    */
   @Nonnull
   public Query limit(int limit) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.limit = limit;
-    return new Query(firestore, path, newOptions);
+    return new Query(firestore, options.toBuilder().setLimit(limit).build());
   }
 
   /**
@@ -690,9 +697,7 @@ public Query limit(int limit) {
    */
   @Nonnull
   public Query offset(int offset) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.offset = offset;
-    return new Query(firestore, path, newOptions);
+    return new Query(firestore, options.toBuilder().setOffset(offset).build());
   }
 
   /**
@@ -705,10 +710,13 @@ public Query offset(int offset) {
    */
   @Nonnull
   public Query startAt(@Nonnull DocumentSnapshot snapshot) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldOrders = createImplicitOrderBy();
-    newOptions.startCursor = createCursor(newOptions.fieldOrders, snapshot, true);
-    return new Query(firestore, path, newOptions);
+    ImmutableList<FieldOrder> fieldOrders = createImplicitOrderBy();
+    Cursor cursor = createCursor(fieldOrders, snapshot, true);
+
+    Builder newOptions = options.toBuilder();
+    newOptions.setFieldOrders(fieldOrders);
+    newOptions.setStartCursor(cursor);
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -720,9 +728,11 @@ public Query startAt(@Nonnull DocumentSnapshot snapshot) {
    */
   @Nonnull
   public Query startAt(Object... fieldValues) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.startCursor = createCursor(newOptions.fieldOrders, fieldValues, true);
-    return new Query(firestore, path, newOptions);
+    Cursor cursor = createCursor(options.getFieldOrders(), fieldValues, true);
+
+    Builder newOptions = options.toBuilder();
+    newOptions.setStartCursor(cursor);
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -754,8 +764,7 @@ public Query select(String... fields) {
    */
   @Nonnull
   public Query select(FieldPath... fieldPaths) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldProjections = new ArrayList<>();
+    ImmutableList.Builder<FieldReference> fieldProjections = ImmutableList.builder();
 
     if (fieldPaths.length == 0) {
       fieldPaths = new FieldPath[] {FieldPath.DOCUMENT_ID};
@@ -764,10 +773,11 @@ public Query select(FieldPath... fieldPaths) {
     for (FieldPath path : fieldPaths) {
       FieldReference fieldReference =
           FieldReference.newBuilder().setFieldPath(path.getEncodedPath()).build();
-      newOptions.fieldProjections.add(fieldReference);
+      fieldProjections.add(fieldReference);
     }
 
-    return new Query(firestore, path, newOptions);
+    Builder newOptions = options.toBuilder().setFieldProjections(fieldProjections.build());
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -780,10 +790,13 @@ public Query select(FieldPath... fieldPaths) {
    */
   @Nonnull
   public Query startAfter(@Nonnull DocumentSnapshot snapshot) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldOrders = createImplicitOrderBy();
-    newOptions.startCursor = createCursor(newOptions.fieldOrders, snapshot, false);
-    return new Query(firestore, path, newOptions);
+    ImmutableList<FieldOrder> fieldOrders = createImplicitOrderBy();
+    Cursor cursor = createCursor(fieldOrders, snapshot, false);
+
+    Builder newOptions = options.toBuilder();
+    newOptions.setFieldOrders(fieldOrders);
+    newOptions.setStartCursor(cursor);
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -796,9 +809,11 @@ public Query startAfter(@Nonnull DocumentSnapshot snapshot) {
    * @return The created Query.
    */
   public Query startAfter(Object... fieldValues) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.startCursor = createCursor(newOptions.fieldOrders, fieldValues, false);
-    return new Query(firestore, path, newOptions);
+    Cursor cursor = createCursor(options.getFieldOrders(), fieldValues, false);
+
+    Builder newOptions = options.toBuilder();
+    newOptions.setStartCursor(cursor);
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -811,10 +826,13 @@ public Query startAfter(Object... fieldValues) {
    */
   @Nonnull
   public Query endBefore(@Nonnull DocumentSnapshot snapshot) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldOrders = createImplicitOrderBy();
-    newOptions.endCursor = createCursor(newOptions.fieldOrders, snapshot, true);
-    return new Query(firestore, path, newOptions);
+    ImmutableList<FieldOrder> fieldOrders = createImplicitOrderBy();
+    Cursor cursor = createCursor(fieldOrders, snapshot, true);
+
+    Builder newOptions = options.toBuilder();
+    newOptions.setFieldOrders(fieldOrders);
+    newOptions.setEndCursor(cursor);
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -827,9 +845,11 @@ public Query endBefore(@Nonnull DocumentSnapshot snapshot) {
    */
   @Nonnull
   public Query endBefore(Object... fieldValues) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.endCursor = createCursor(newOptions.fieldOrders, fieldValues, true);
-    return new Query(firestore, path, newOptions);
+    Cursor cursor = createCursor(options.getFieldOrders(), fieldValues, true);
+
+    Builder newOptions = options.toBuilder();
+    newOptions.setEndCursor(cursor);
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -841,9 +861,11 @@ public Query endBefore(Object... fieldValues) {
    */
   @Nonnull
   public Query endAt(Object... fieldValues) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.endCursor = createCursor(newOptions.fieldOrders, fieldValues, false);
-    return new Query(firestore, path, newOptions);
+    Cursor cursor = createCursor(options.getFieldOrders(), fieldValues, false);
+
+    Builder newOptions = options.toBuilder();
+    newOptions.setEndCursor(cursor);
+    return new Query(firestore, newOptions.build());
   }
 
   /**
@@ -856,20 +878,25 @@ public Query endAt(Object... fieldValues) {
    */
   @Nonnull
   public Query endAt(@Nonnull DocumentSnapshot snapshot) {
-    QueryOptions newOptions = new QueryOptions(options);
-    newOptions.fieldOrders = createImplicitOrderBy();
-    newOptions.endCursor = createCursor(newOptions.fieldOrders, snapshot, false);
-    return new Query(firestore, path, newOptions);
+    ImmutableList<FieldOrder> fieldOrders = createImplicitOrderBy();
+    Cursor cursor = createCursor(fieldOrders, snapshot, false);
+
+    Builder newOptions = options.toBuilder();
+    newOptions.setFieldOrders(fieldOrders);
+    newOptions.setEndCursor(cursor);
+    return new Query(firestore, newOptions.build());
   }
 
   /** Build the final Firestore query. */
   StructuredQuery.Builder buildQuery() {
     StructuredQuery.Builder structuredQuery = StructuredQuery.newBuilder();
-    structuredQuery.addFrom(
-        StructuredQuery.CollectionSelector.newBuilder().setCollectionId(path.getId()));
+    CollectionSelector.Builder collectionSelector = CollectionSelector.newBuilder();
+    collectionSelector.setCollectionId(options.getCollectionId());
+    collectionSelector.setAllDescendants(options.getAllDescendants());
+    structuredQuery.addFrom(collectionSelector);
 
-    if (options.fieldFilters.size() == 1) {
-      Filter filter = options.fieldFilters.get(0).toProto();
+    if (options.getFieldFilters().size() == 1) {
+      Filter filter = options.getFieldFilters().get(0).toProto();
       if (filter.hasFieldFilter()) {
         structuredQuery.getWhereBuilder().setFieldFilter(filter.getFieldFilter());
       } else {
@@ -877,42 +904,42 @@ StructuredQuery.Builder buildQuery() {
             filter.hasUnaryFilter(), "Expected a UnaryFilter or a FieldFilter.");
         structuredQuery.getWhereBuilder().setUnaryFilter(filter.getUnaryFilter());
       }
-    } else if (options.fieldFilters.size() > 1) {
+    } else if (options.getFieldFilters().size() > 1) {
       Filter.Builder filter = Filter.newBuilder();
       StructuredQuery.CompositeFilter.Builder compositeFilter =
           StructuredQuery.CompositeFilter.newBuilder();
       compositeFilter.setOp(CompositeFilter.Operator.AND);
-      for (FieldFilter fieldFilter : options.fieldFilters) {
+      for (FieldFilter fieldFilter : options.getFieldFilters()) {
         compositeFilter.addFilters(fieldFilter.toProto());
       }
       filter.setCompositeFilter(compositeFilter.build());
       structuredQuery.setWhere(filter.build());
     }
 
-    if (!options.fieldOrders.isEmpty()) {
-      for (FieldOrder order : options.fieldOrders) {
+    if (!options.getFieldOrders().isEmpty()) {
+      for (FieldOrder order : options.getFieldOrders()) {
         structuredQuery.addOrderBy(order.toProto());
       }
     }
 
-    if (!options.fieldProjections.isEmpty()) {
-      structuredQuery.getSelectBuilder().addAllFields(options.fieldProjections);
+    if (!options.getFieldProjections().isEmpty()) {
+      structuredQuery.getSelectBuilder().addAllFields(options.getFieldProjections());
     }
 
-    if (options.limit != -1) {
-      structuredQuery.setLimit(Int32Value.newBuilder().setValue(options.limit));
+    if (options.getLimit() != null) {
+      structuredQuery.setLimit(Int32Value.newBuilder().setValue(options.getLimit()));
     }
 
-    if (options.offset != -1) {
-      structuredQuery.setOffset(options.offset);
+    if (options.getOffset() != null) {
+      structuredQuery.setOffset(options.getOffset());
     }
 
-    if (options.startCursor != null) {
-      structuredQuery.setStartAt(options.startCursor);
+    if (options.getStartCursor() != null) {
+      structuredQuery.setStartAt(options.getStartCursor());
     }
 
-    if (options.endCursor != null) {
-      structuredQuery.setEndAt(options.endCursor);
+    if (options.getEndCursor() != null) {
+      structuredQuery.setEndAt(options.getEndCursor());
     }
 
     return structuredQuery;
@@ -963,7 +990,7 @@ Timestamp getReadTime() {
   private void stream(
       final QuerySnapshotObserver documentObserver, @Nullable ByteString transactionId) {
     RunQueryRequest.Builder request = RunQueryRequest.newBuilder();
-    request.setStructuredQuery(buildQuery()).setParent(path.getParent().toString());
+    request.setStructuredQuery(buildQuery()).setParent(options.getParentPath().toString());
 
     if (transactionId != null) {
       request.setTransaction(transactionId);
@@ -1096,13 +1123,13 @@ Comparator<QueryDocumentSnapshot> comparator() {
       @Override
       public int compare(QueryDocumentSnapshot doc1, QueryDocumentSnapshot doc2) {
         // Add implicit sorting by name, using the last specified direction.
+        ImmutableList<FieldOrder> fieldOrders = options.getFieldOrders();
         Direction lastDirection =
-            options.fieldOrders.isEmpty()
+            fieldOrders.isEmpty()
                 ? Direction.ASCENDING
-                : options.fieldOrders.get(options.fieldOrders.size() - 1).direction;
+                : fieldOrders.get(fieldOrders.size() - 1).direction;
 
-        List<FieldOrder> orderBys = new ArrayList<>();
-        orderBys.addAll(options.fieldOrders);
+        List<FieldOrder> orderBys = new ArrayList<>(fieldOrders);
         orderBys.add(new FieldOrder(FieldPath.DOCUMENT_ID, lastDirection));
 
         for (FieldOrder orderBy : orderBys) {
@@ -1135,8 +1162,15 @@ public int compare(QueryDocumentSnapshot doc1, QueryDocumentSnapshot doc2) {
     };
   }
 
-  ResourcePath getResourcePath() {
-    return path;
+  /**
+   * Helper method to append an element to an existing ImmutableList. Returns the newly created
+   * list.
+   */
+  private <T> ImmutableList<T> append(ImmutableList<T> existingList, T newElement) {
+    ImmutableList.Builder<T> builder = ImmutableList.builder();
+    builder.addAll(existingList);
+    builder.add(newElement);
+    return builder.build();
   }
 
   /**
@@ -1154,13 +1188,11 @@ public boolean equals(Object obj) {
       return false;
     }
     Query query = (Query) obj;
-    return Objects.equals(path, query.path)
-        && Objects.equals(firestore, query.firestore)
-        && Objects.equals(options, query.options);
+    return Objects.equals(firestore, query.firestore) && Objects.equals(options, query.options);
   }
 
   @Override
   public int hashCode() {
-    return Objects.hash(path, firestore, options);
+    return Objects.hash(firestore, options);
   }
 }
diff --git a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Watch.java b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Watch.java
index 6d937aa2306e..f0783924e127 100644
--- a/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Watch.java
+++ b/google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Watch.java
@@ -172,7 +172,7 @@ static Watch forQuery(Query query) {
     target.setQuery(
         QueryTarget.newBuilder()
             .setStructuredQuery(query.buildQuery())
-            .setParent(query.getResourcePath().getParent().getName())
+            .setParent(query.options.getParentPath().getName())
             .build());
     target.setTargetId(WATCH_TARGET_ID);
 
diff --git a/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/LocalFirestoreHelper.java b/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/LocalFirestoreHelper.java
index c57a8e024fbd..caaaa8aca884 100644
--- a/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/LocalFirestoreHelper.java
+++ b/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/LocalFirestoreHelper.java
@@ -43,6 +43,7 @@
 import com.google.firestore.v1.RunQueryRequest;
 import com.google.firestore.v1.RunQueryResponse;
 import com.google.firestore.v1.StructuredQuery;
+import com.google.firestore.v1.StructuredQuery.CollectionSelector;
 import com.google.firestore.v1.StructuredQuery.CompositeFilter;
 import com.google.firestore.v1.StructuredQuery.FieldFilter;
 import com.google.firestore.v1.StructuredQuery.UnaryFilter;
@@ -73,6 +74,7 @@
 public final class LocalFirestoreHelper {
 
   public static final String DATABASE_NAME;
+  public static final String COLLECTION_ID;
   public static final String DOCUMENT_PATH;
   public static final String DOCUMENT_NAME;
   public static final ByteString TRANSACTION_ID;
@@ -467,16 +469,21 @@ public static StructuredQuery unaryFilter(StructuredQuery.UnaryFilter.Operator o
   }
 
   public static RunQueryRequest query(StructuredQuery... query) {
-    return query(null, query);
+    return query(null, false, query);
   }
 
   public static RunQueryRequest query(
-      @Nullable ByteString transactionId, StructuredQuery... query) {
+      @Nullable ByteString transactionId, boolean allDescendants, StructuredQuery... query) {
     RunQueryRequest.Builder request = RunQueryRequest.newBuilder();
     request.setParent(LocalFirestoreHelper.DATABASE_NAME + "/documents");
     StructuredQuery.Builder structuredQuery = request.getStructuredQueryBuilder();
-    structuredQuery.addFrom(
-        StructuredQuery.CollectionSelector.newBuilder().setCollectionId("coll"));
+
+    CollectionSelector collectionSelector =
+        CollectionSelector.newBuilder()
+            .setCollectionId("coll")
+            .setAllDescendants(allDescendants)
+            .build();
+    structuredQuery.addFrom(collectionSelector);
 
     for (StructuredQuery option : query) {
       structuredQuery.mergeFrom(option);
@@ -588,6 +595,10 @@ public static Value object(String key, Value value) {
     return result.build();
   }
 
+  public static Value reference(String value) {
+    return Value.newBuilder().setReferenceValue(value).build();
+  }
+
   public static StructuredQuery.FieldReference.Builder field(String fieldPath) {
     return StructuredQuery.FieldReference.newBuilder().setFieldPath(fieldPath);
   }
@@ -686,6 +697,7 @@ public boolean equals(Object o) {
     BLOB = Blob.fromBytes(new byte[] {1, 2, 3});
 
     DATABASE_NAME = "projects/test-project/databases/(default)";
+    COLLECTION_ID = "coll";
     DOCUMENT_PATH = "coll/doc";
     DOCUMENT_NAME = DATABASE_NAME + "/documents/" + DOCUMENT_PATH;
 
diff --git a/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/QueryTest.java b/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/QueryTest.java
index 770864f6ee31..173bbbff6ba8 100644
--- a/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/QueryTest.java
+++ b/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/QueryTest.java
@@ -16,6 +16,7 @@
 
 package com.google.cloud.firestore;
 
+import static com.google.cloud.firestore.LocalFirestoreHelper.COLLECTION_ID;
 import static com.google.cloud.firestore.LocalFirestoreHelper.DOCUMENT_NAME;
 import static com.google.cloud.firestore.LocalFirestoreHelper.SINGLE_FIELD_SNAPSHOT;
 import static com.google.cloud.firestore.LocalFirestoreHelper.endAt;
@@ -25,6 +26,7 @@
 import static com.google.cloud.firestore.LocalFirestoreHelper.order;
 import static com.google.cloud.firestore.LocalFirestoreHelper.query;
 import static com.google.cloud.firestore.LocalFirestoreHelper.queryResponse;
+import static com.google.cloud.firestore.LocalFirestoreHelper.reference;
 import static com.google.cloud.firestore.LocalFirestoreHelper.select;
 import static com.google.cloud.firestore.LocalFirestoreHelper.startAt;
 import static com.google.cloud.firestore.LocalFirestoreHelper.unaryFilter;
@@ -72,7 +74,7 @@ public class QueryTest {
 
   @Before
   public void before() {
-    query = firestoreMock.collection("coll");
+    query = firestoreMock.collection(COLLECTION_ID);
   }
 
   @Test
@@ -183,11 +185,7 @@ public void withDocumentIdFilter() throws Exception {
     query.whereEqualTo(FieldPath.documentId(), "doc").get().get();
 
     RunQueryRequest expectedRequest =
-        query(
-            filter(
-                Operator.EQUAL,
-                "__name__",
-                Value.newBuilder().setReferenceValue(DOCUMENT_NAME).build()));
+        query(filter(Operator.EQUAL, "__name__", reference(DOCUMENT_NAME)));
 
     assertEquals(expectedRequest, runQuery.getValue());
   }
@@ -287,8 +285,7 @@ public void withDocumentSnapshotCursor() throws Exception {
 
     query.startAt(SINGLE_FIELD_SNAPSHOT).get();
 
-    Value documentBoundary =
-        Value.newBuilder().setReferenceValue(query.getResourcePath().toString() + "/doc").build();
+    Value documentBoundary = reference(DOCUMENT_NAME);
 
     RunQueryRequest queryRequest =
         query(
@@ -309,8 +306,7 @@ public void withDocumentIdAndDocumentSnapshotCursor() throws Exception {
 
     query.orderBy(FieldPath.documentId()).startAt(SINGLE_FIELD_SNAPSHOT).get();
 
-    Value documentBoundary =
-        Value.newBuilder().setReferenceValue(query.getResourcePath().toString() + "/doc").build();
+    Value documentBoundary = reference(DOCUMENT_NAME);
 
     RunQueryRequest queryRequest =
         query(
@@ -331,8 +327,7 @@ public void withExtractedDirectionForDocumentSnapshotCursor() throws Exception {
 
     query.orderBy("foo", Query.Direction.DESCENDING).startAt(SINGLE_FIELD_SNAPSHOT).get();
 
-    Value documentBoundary =
-        Value.newBuilder().setReferenceValue(query.getResourcePath().toString() + "/doc").build();
+    Value documentBoundary = reference(DOCUMENT_NAME);
 
     RunQueryRequest queryRequest =
         query(
@@ -360,8 +355,7 @@ public void withInequalityFilterForDocumentSnapshotCursor() throws Exception {
         .startAt(SINGLE_FIELD_SNAPSHOT)
         .get();
 
-    Value documentBoundary =
-        Value.newBuilder().setReferenceValue(query.getResourcePath().toString() + "/doc").build();
+    Value documentBoundary = reference(DOCUMENT_NAME);
 
     RunQueryRequest queryRequest =
         query(
@@ -387,8 +381,7 @@ public void withEqualityFilterForDocumentSnapshotCursor() throws Exception {
 
     query.whereEqualTo("foo", "bar").startAt(SINGLE_FIELD_SNAPSHOT).get();
 
-    Value documentBoundary =
-        Value.newBuilder().setReferenceValue(query.getResourcePath().toString() + "/doc").build();
+    Value documentBoundary = reference(DOCUMENT_NAME);
 
     RunQueryRequest queryRequest =
         query(
@@ -408,10 +401,9 @@ public void withStartAt() throws Exception {
             streamObserverCapture.capture(),
             Matchers.<ServerStreamingCallable>any());
 
-    query.orderBy("foo").orderBy(FieldPath.documentId()).startAt("bar", "foo").get().get();
+    query.orderBy("foo").orderBy(FieldPath.documentId()).startAt("bar", "doc").get().get();
 
-    Value documentBoundary =
-        Value.newBuilder().setReferenceValue(query.getResourcePath().toString() + "/foo").build();
+    Value documentBoundary = reference(DOCUMENT_NAME);
 
     RunQueryRequest queryRequest =
         query(
@@ -505,6 +497,43 @@ public void withEndAt() throws Exception {
     assertEquals(queryRequest, runQuery.getValue());
   }
 
+  @Test
+  public void withCollectionGroup() throws Exception {
+    doAnswer(queryResponse())
+        .when(firestoreMock)
+        .streamRequest(
+            runQuery.capture(),
+            streamObserverCapture.capture(),
+            Matchers.<ServerStreamingCallable>any());
+
+    Query query = firestoreMock.collectionGroup(COLLECTION_ID);
+    query = query.whereGreaterThan(FieldPath.documentId(), "coll/doc");
+    query = query.orderBy(FieldPath.documentId());
+    query = query.endAt("coll/doc");
+    query.get();
+
+    RunQueryRequest queryRequest =
+        query(
+            /* transactionId= */ null,
+            /* allDescendants= */ true,
+            filter(Operator.GREATER_THAN, "__name__", reference(DOCUMENT_NAME)),
+            order("__name__", StructuredQuery.Direction.ASCENDING),
+            endAt(reference(DOCUMENT_NAME), false));
+
+    assertEquals(queryRequest, runQuery.getValue());
+  }
+
+  @Test
+  public void collectionGroupCannotContainSlashes() {
+    try {
+      Query query = firestoreMock.collectionGroup("foo/bar");
+      fail();
+    } catch (IllegalArgumentException e) {
+      assertEquals(
+          "Invalid collectionId 'foo/bar'. Collection IDs must not contain '/'.", e.getMessage());
+    }
+  }
+
   @Test(expected = IllegalStateException.class)
   public void overspecifiedCursor() throws Exception {
     query.orderBy("foo").startAt("foo", "bar", "bar", "foo");
diff --git a/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/TransactionTest.java b/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/TransactionTest.java
index 0a227af0bbbf..8895bca4f4a7 100644
--- a/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/TransactionTest.java
+++ b/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/TransactionTest.java
@@ -459,7 +459,7 @@ public QuerySnapshot updateCallback(Transaction transaction)
     assertEquals(3, requests.size());
 
     assertEquals(begin(), requests.get(0));
-    assertEquals(query(TRANSACTION_ID), requests.get(1));
+    assertEquals(query(TRANSACTION_ID, /* allDescendants= */ false), requests.get(1));
     assertEquals(commit(TRANSACTION_ID), requests.get(2));
   }
 
diff --git a/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/it/ITSystemTest.java b/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/it/ITSystemTest.java
index 92d771ecf454..45c095d0636c 100644
--- a/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/it/ITSystemTest.java
+++ b/google-cloud-clients/google-cloud-firestore/src/test/java/com/google/cloud/firestore/it/ITSystemTest.java
@@ -17,6 +17,7 @@
 package com.google.cloud.firestore.it;
 
 import static com.google.cloud.firestore.LocalFirestoreHelper.map;
+import static java.util.Arrays.asList;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -33,6 +34,7 @@
 import com.google.cloud.firestore.DocumentSnapshot;
 import com.google.cloud.firestore.EventListener;
 import com.google.cloud.firestore.FieldMask;
+import com.google.cloud.firestore.FieldPath;
 import com.google.cloud.firestore.FieldValue;
 import com.google.cloud.firestore.Firestore;
 import com.google.cloud.firestore.FirestoreException;
@@ -108,6 +110,14 @@ private DocumentReference addDocument(String key, Object value, Object... fields
     return documentReference;
   }
 
+  private List<String> querySnapshotToIds(QuerySnapshot querySnapshot) {
+    List<String> documentIds = new ArrayList<>();
+    for (QueryDocumentSnapshot snapshot : querySnapshot.getDocuments()) {
+      documentIds.add(snapshot.getId());
+    }
+    return documentIds;
+  }
+
   @Test
   public void getAll() throws Exception {
     DocumentReference ref1 = randomColl.document("doc1");
@@ -996,6 +1006,128 @@ public void arrayOperators() throws ExecutionException, InterruptedException {
     assertTrue(containsQuery.get().get().isEmpty());
   }
 
+  @Test
+  public void testCollectionGroupQueries() throws ExecutionException, InterruptedException {
+    // Use `randomColl` to get a random collection group name to use but ensure it starts with 'b'
+    // for predictable ordering.
+    String collectionGroup = "b" + randomColl.getId();
+
+    String[] docPaths =
+        new String[] {
+          "abc/123/${collectionGroup}/cg-doc1",
+          "abc/123/${collectionGroup}/cg-doc2",
+          "${collectionGroup}/cg-doc3",
+          "${collectionGroup}/cg-doc4",
+          "def/456/${collectionGroup}/cg-doc5",
+          "${collectionGroup}/virtual-doc/nested-coll/not-cg-doc",
+          "x${collectionGroup}/not-cg-doc",
+          "${collectionGroup}x/not-cg-doc",
+          "abc/123/${collectionGroup}x/not-cg-doc",
+          "abc/123/x${collectionGroup}/not-cg-doc",
+          "abc/${collectionGroup}"
+        };
+    WriteBatch batch = firestore.batch();
+    for (String path : docPaths) {
+      batch.set(
+          firestore.document(path.replace("${collectionGroup}", collectionGroup)), map("x", 1));
+    }
+    batch.commit().get();
+
+    QuerySnapshot querySnapshot = firestore.collectionGroup(collectionGroup).get().get();
+    assertEquals(
+        asList("cg-doc1", "cg-doc2", "cg-doc3", "cg-doc4", "cg-doc5"),
+        querySnapshotToIds(querySnapshot));
+  }
+
+  @Test
+  public void testCollectionGroupQueriesWithStartAtEndAtWithArbitraryDocumentIds()
+      throws ExecutionException, InterruptedException {
+    // Use `randomColl` to get a random collection group name to use but ensure it starts with 'b'
+    // for predictable ordering.
+    String collectionGroup = "b" + randomColl.getId();
+
+    String[] docPaths =
+        new String[] {
+          "a/a/${collectionGroup}/cg-doc1",
+          "a/b/a/b/${collectionGroup}/cg-doc2",
+          "a/b/${collectionGroup}/cg-doc3",
+          "a/b/c/d/${collectionGroup}/cg-doc4",
+          "a/c/${collectionGroup}/cg-doc5",
+          "${collectionGroup}/cg-doc6",
+          "a/b/nope/nope"
+        };
+    WriteBatch batch = firestore.batch();
+    for (String path : docPaths) {
+      batch.set(
+          firestore.document(path.replace("${collectionGroup}", collectionGroup)), map("x", 1));
+    }
+    batch.commit().get();
+
+    QuerySnapshot querySnapshot =
+        firestore
+            .collectionGroup(collectionGroup)
+            .orderBy(FieldPath.documentId())
+            .startAt("a/b")
+            .endAt("a/b0")
+            .get()
+            .get();
+    assertEquals(asList("cg-doc2", "cg-doc3", "cg-doc4"), querySnapshotToIds(querySnapshot));
+
+    querySnapshot =
+        firestore
+            .collectionGroup(collectionGroup)
+            .orderBy(FieldPath.documentId())
+            .startAfter("a/b")
+            .endBefore("a/b/" + collectionGroup + "/cg-doc3")
+            .get()
+            .get();
+    assertEquals(asList("cg-doc2"), querySnapshotToIds(querySnapshot));
+  }
+
+  @Test
+  public void testCollectionGroupQueriesWithWhereFiltersOnArbitraryDocumentIds()
+      throws ExecutionException, InterruptedException {
+    // Use `randomColl` to get a random collection group name to use but ensure it starts with 'b'
+    // for predictable ordering.
+    String collectionGroup = "b" + randomColl.getId();
+
+    String[] docPaths =
+        new String[] {
+          "a/a/${collectionGroup}/cg-doc1",
+          "a/b/a/b/${collectionGroup}/cg-doc2",
+          "a/b/${collectionGroup}/cg-doc3",
+          "a/b/c/d/${collectionGroup}/cg-doc4",
+          "a/c/${collectionGroup}/cg-doc5",
+          "${collectionGroup}/cg-doc6",
+          "a/b/nope/nope"
+        };
+
+    WriteBatch batch = firestore.batch();
+    for (String path : docPaths) {
+      batch.set(
+          firestore.document(path.replace("${collectionGroup}", collectionGroup)), map("x", 1));
+    }
+    batch.commit().get();
+
+    QuerySnapshot querySnapshot =
+        firestore
+            .collectionGroup(collectionGroup)
+            .whereGreaterThanOrEqualTo(FieldPath.documentId(), "a/b")
+            .whereLessThanOrEqualTo(FieldPath.documentId(), "a/b0")
+            .get()
+            .get();
+    assertEquals(asList("cg-doc2", "cg-doc3", "cg-doc4"), querySnapshotToIds(querySnapshot));
+
+    querySnapshot =
+        firestore
+            .collectionGroup(collectionGroup)
+            .whereGreaterThan(FieldPath.documentId(), "a/b")
+            .whereLessThan(FieldPath.documentId(), "a/b/" + collectionGroup + "/cg-doc3")
+            .get()
+            .get();
+    assertEquals(asList("cg-doc2"), querySnapshotToIds(querySnapshot));
+  }
+
   @Test
   public void integerIncrement() throws ExecutionException, InterruptedException {
     DocumentReference docRef = randomColl.document();