feat(bigtable): reverse scans

google/cloud/bigtable/data_connection.cc

@@ -77,10 +77,15 @@ future<std::vector<FailedMutation>> DataConnection::AsyncBulkApply(
 RowReader DataConnection::ReadRows(std::string const& table_name,
                                    RowSet row_set, std::int64_t rows_limit,
                                    Filter filter) {
+  auto const& options = google::cloud::internal::CurrentOptions();
   return ReadRowsFull(ReadRowsParams{
       std::move(table_name),
-      google::cloud::internal::CurrentOptions().get<AppProfileIdOption>(),
-      std::move(row_set), rows_limit, std::move(filter)});
+      options.get<AppProfileIdOption>(),
+      std::move(row_set),
+      rows_limit,
+      std::move(filter),
+      options.get<ReverseScanOption>(),
+  });
 }
 
 // NOLINTNEXTLINE(performance-unnecessary-value-param)

google/cloud/bigtable/data_connection.h

@@ -49,6 +49,7 @@ struct ReadRowsParams {
   RowSet row_set;
   std::int64_t rows_limit;
   Filter filter = Filter::PassAllFilter();
+  bool reverse = false;
 };
 
 /**

google/cloud/bigtable/examples/read_snippets.cc

@@ -334,6 +334,27 @@ void ReadFilter(google::cloud::bigtable::Table table,
   (std::move(table));
 }
 
+void ReadRowsReverse(google::cloud::bigtable::Table table,
+                     std::vector<std::string> const&) {
+  //! [reverse scan] [START bigtable_reverse_scan]
+  namespace cbt = ::google::cloud::bigtable;
+  using ::google::cloud::Options;
+  using ::google::cloud::StatusOr;
+  [](cbt::Table table) {
+    // Read and print the rows.
+    auto reader = table.ReadRows(
+        cbt::RowRange::RightOpen("phone#5c10102", "phone#5c10103"), 3,
+        cbt::Filter::PassAllFilter(),
+        Options{}.set<cbt::ReverseScanOption>(true));
+    for (StatusOr<cbt::Row>& row : reader) {
+      if (!row) throw std::move(row).status();
+      PrintRow(*row);
+    }
+  }
+  //! [reverse scan] [END bigtable_reverse_scan]
+  (std::move(table));
+}
+
 void RunAll(std::vector<std::string> const& argv) {
   namespace examples = ::google::cloud::bigtable::examples;
   namespace cbt = ::google::cloud::bigtable;
@@ -391,6 +412,10 @@ void RunAll(std::vector<std::string> const& argv) {
   ReadFilter(table, {});
   std::cout << "Running ReadRowsWithLimit() example" << std::endl;
   ReadRowsWithLimit(table, {"5"});
+  if (!google::cloud::bigtable::examples::UsingEmulator()) {
+    std::cout << "Running ReadRowsReverse() example" << std::endl;
+    ReadRowsReverse(table, {});
+  }
 
   std::cout << "Running ReadKeySet() example" << std::endl;
   ReadKeysSet({table.project_id(), table.instance_id(), table.table_id(),
@@ -415,6 +440,7 @@ int main(int argc, char* argv[]) try {
       MakeCommandEntry("read-row-ranges", {}, ReadRowRanges),
       MakeCommandEntry("read-row-prefix", {}, ReadRowPrefix),
       MakeCommandEntry("read-filter", {}, ReadFilter),
+      MakeCommandEntry("read-rows-reverse", {}, ReadRowsReverse),
       {"auto", RunAll},
   };
 

google/cloud/bigtable/internal/data_connection_impl.cc

@@ -178,7 +178,7 @@ bigtable::RowReader DataConnectionImpl::ReadRowsFull(
   auto impl = std::make_shared<DefaultRowReader>(
       stub_, std::move(params.app_profile_id), std::move(params.table_name),
       std::move(params.row_set), params.rows_limit, std::move(params.filter),
-      false, retry_policy(), backoff_policy());
+      params.reverse, retry_policy(), backoff_policy());
   return MakeRowReader(std::move(impl));
 }
 
@@ -374,7 +374,7 @@ void DataConnectionImpl::AsyncReadRows(
     std::function<future<bool>(bigtable::Row)> on_row,
     std::function<void(Status)> on_finish, bigtable::RowSet row_set,
     std::int64_t rows_limit, bigtable::Filter filter) {
-  auto reverse = false;
+  auto reverse = internal::CurrentOptions().get<bigtable::ReverseScanOption>();
   bigtable_internal::AsyncRowReader::Create(
       background_->cq(), stub_, app_profile_id(), table_name, std::move(on_row),
       std::move(on_finish), std::move(row_set), rows_limit, std::move(filter),

google/cloud/bigtable/internal/data_connection_impl_test.cc

@@ -15,6 +15,7 @@
 #include "google/cloud/bigtable/internal/data_connection_impl.h"
 #include "google/cloud/bigtable/data_connection.h"
 #include "google/cloud/bigtable/internal/defaults.h"
+#include "google/cloud/bigtable/options.h"
 #include "google/cloud/bigtable/testing/mock_bigtable_stub.h"
 #include "google/cloud/bigtable/testing/mock_policies.h"
 #include "google/cloud/common_options.h"
@@ -40,6 +41,7 @@ using ::google::cloud::bigtable::DataBackoffPolicyOption;
 using ::google::cloud::bigtable::DataLimitedErrorCountRetryPolicy;
 using ::google::cloud::bigtable::DataRetryPolicyOption;
 using ::google::cloud::bigtable::IdempotentMutationPolicyOption;
+using ::google::cloud::bigtable::ReverseScanOption;
 using ::google::cloud::bigtable::testing::MockAsyncReadRowsStream;
 using ::google::cloud::bigtable::testing::MockBigtableStub;
 using ::google::cloud::bigtable::testing::MockIdempotentMutationPolicy;
@@ -705,6 +707,23 @@ TEST(DataConnectionTest, ReadRows) {
   EXPECT_EQ(reader.begin(), reader.end());
 }
 
+TEST(DataConnectionTest, ReadRowsReverseScan) {
+  auto mock = std::make_shared<MockBigtableStub>();
+  EXPECT_CALL(*mock, ReadRows)
+      .WillOnce([](auto, google::bigtable::v2::ReadRowsRequest const& request) {
+        EXPECT_TRUE(request.reversed());
+
+        auto stream = std::make_unique<MockReadRowsStream>();
+        EXPECT_CALL(*stream, Read).WillOnce(Return(Status()));
+        return stream;
+      });
+
+  auto conn = TestConnection(std::move(mock));
+  internal::OptionsSpan span(CallOptions().set<ReverseScanOption>(true));
+  auto reader = conn->ReadRows(kTableName, TestRowSet(), 42, TestFilter());
+  EXPECT_EQ(reader.begin(), reader.end());
+}
+
 // The DefaultRowReader is tested extensively in `default_row_reader_test.cc`.
 // In this test, we just verify that the configuration is passed along.
 TEST(DataConnectionTest, ReadRowsFull) {
@@ -716,7 +735,7 @@ TEST(DataConnectionTest, ReadRowsFull) {
         EXPECT_EQ(42, request.rows_limit());
         EXPECT_THAT(request, HasTestRowSet());
         EXPECT_THAT(request.filter(), IsTestFilter());
-        EXPECT_FALSE(request.reversed());
+        EXPECT_TRUE(request.reversed());
 
         auto stream = std::make_unique<MockReadRowsStream>();
         EXPECT_CALL(*stream, Read).WillOnce(Return(Status()));
@@ -726,7 +745,7 @@ TEST(DataConnectionTest, ReadRowsFull) {
   auto conn = TestConnection(std::move(mock));
   internal::OptionsSpan span(CallOptions());
   auto reader = conn->ReadRowsFull(bigtable::ReadRowsParams{
-      kTableName, kAppProfile, TestRowSet(), 42, TestFilter()});
+      kTableName, kAppProfile, TestRowSet(), 42, TestFilter(), true});
   EXPECT_EQ(reader.begin(), reader.end());
 }
 
@@ -1478,6 +1497,32 @@ TEST(DataConnectionTest, AsyncReadRows) {
                       TestFilter());
 }
 
+TEST(DataConnectionTest, AsyncReadRowsReverseScan) {
+  auto mock = std::make_shared<MockBigtableStub>();
+  EXPECT_CALL(*mock, AsyncReadRows)
+      .WillOnce(
+          [](CompletionQueue const&, auto, v2::ReadRowsRequest const& request) {
+            EXPECT_TRUE(request.reversed());
+            using ErrorStream =
+                internal::AsyncStreamingReadRpcError<v2::ReadRowsResponse>;
+            return std::make_unique<ErrorStream>(PermanentError());
+          });
+
+  MockFunction<future<bool>(bigtable::Row const&)> on_row;
+  EXPECT_CALL(on_row, Call).Times(0);
+
+  MockFunction<void(Status)> on_finish;
+  EXPECT_CALL(on_finish, Call).WillOnce([](Status const& status) {
+    EXPECT_THAT(status, StatusIs(StatusCode::kPermissionDenied));
+  });
+
+  auto conn = TestConnection(std::move(mock));
+  internal::OptionsSpan span(CallOptions().set<ReverseScanOption>(true));
+  conn->AsyncReadRows(kTableName, on_row.AsStdFunction(),
+                      on_finish.AsStdFunction(), TestRowSet(), 42,
+                      TestFilter());
+}
+
 TEST(DataConnectionTest, AsyncReadRowEmpty) {
   auto mock = std::make_shared<MockBigtableStub>();
   EXPECT_CALL(*mock, AsyncReadRows)

google/cloud/bigtable/options.h

@@ -76,6 +76,28 @@ struct AppProfileIdOption {
   using Type = std::string;
 };
 
+/**
+ * Read rows in reverse order.
+ *
+ * The rows will be streamed in reverse lexicographic order of the keys. This is
+ * particularly useful to get the last N records before a key.
+ *
+ * This option does not affect the contents of the rows, just the order that
+ * the rows are returned.
+ *
+ * @note When using this option, the order of row keys in a `bigtable::RowRange`
+ * does not change. The row keys still must be supplied in lexicographic order.
+ *
+ * @snippet read_snippets.cc reverse scan
+ *
+ * @see https://cloud.google.com/bigtable/docs/reads#reverse-scan
+ *
+ * @ingroup bigtable-options
+ */
+struct ReverseScanOption {
+  using Type = bool;
+};
+
 /**
  * The endpoint for data operations.
  *

google/cloud/bigtable/tests/data_integration_test.cc

@@ -198,6 +198,12 @@ TEST_P(DataIntegrationTest, TableReadRowsAllRows) {
 
   auto read4 = table.ReadRows(RowSet(), Filter::PassAllFilter());
   CheckEqualUnordered(created, MoveCellsFromReader(read4));
+
+  if (GetParam() == "with-data-connection" && !UsingCloudBigtableEmulator()) {
+    auto read5 = table.ReadRows(RowSet(), Filter::PassAllFilter(),
+                                Options{}.set<ReverseScanOption>(true));
+    CheckEqualUnordered(created, MoveCellsFromReader(read5));
+  }
 }
 
 TEST_P(DataIntegrationTest, TableReadRowsPartialRows) {