[WIP] ARROW-11928: [C++] Execution engine API

cpp/CMakeLists.txt

@@ -342,6 +342,10 @@ if(ARROW_CUDA
   set(ARROW_IPC ON)
 endif()
 
+if(ARROW_ENGINE)
+  set(ARROW_COMPUTE ON)
+endif()
+
 if(ARROW_DATASET)
   set(ARROW_COMPUTE ON)
   set(ARROW_FILESYSTEM ON)

cpp/cmake_modules/DefineOptions.cmake

@@ -211,6 +211,8 @@ if("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
 
   define_option(ARROW_DATASET "Build the Arrow Dataset Modules" OFF)
 
+  define_option(ARROW_ENGINE "Build the Arrow Execution Engine" OFF)
+
   define_option(ARROW_FILESYSTEM "Build the Arrow Filesystem Layer" OFF)
 
   define_option(ARROW_FLIGHT

cpp/src/arrow/CMakeLists.txt

@@ -409,6 +409,10 @@ if(ARROW_COMPUTE)
   endif()
 endif()
 
+if(ARROW_ENGINE)
+  list(APPEND ARROW_SRCS engine/exec_plan.cc engine/query_plan.cc)
+endif()
+
 if(ARROW_FILESYSTEM)
   if(ARROW_HDFS)
     add_definitions(-DARROW_HDFS)
@@ -671,6 +675,10 @@ if(ARROW_DATASET)
   add_subdirectory(dataset)
 endif()
 
+if(ARROW_ENGINE)
+  add_subdirectory(engine)
+endif()
+
 if(ARROW_FILESYSTEM)
   add_subdirectory(filesystem)
 endif()

cpp/src/arrow/compute/type_fwd.h

@@ -29,6 +29,7 @@ struct FunctionOptions;
 
 struct CastOptions;
 
+class ExecBatch;
 class ExecContext;
 class KernelContext;
 

cpp/src/arrow/engine/CMakeLists.txt

@@ -0,0 +1,19 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+
+# Headers: top level
+arrow_install_all_headers("arrow/engine")

cpp/src/arrow/engine/api.h

@@ -0,0 +1,20 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#pragma once
+
+#include "arrow/engine/query_plan.h"  // IWYU pragma: export

cpp/src/arrow/engine/exec_plan.cc

@@ -0,0 +1,131 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#include "arrow/engine/exec_plan.h"
+
+#include "arrow/compute/exec.h"
+#include "arrow/engine/query_plan.h"
+#include "arrow/result.h"
+#include "arrow/status.h"
+#include "arrow/util/checked_cast.h"
+#include "arrow/util/future.h"
+#include "arrow/util/logging.h"
+#include "arrow/util/thread_pool.h"
+
+namespace arrow {
+
+using internal::checked_cast;
+
+namespace engine {
+
+ExecNode::InputBatch::InputBatch(std::vector<util::optional<compute::ExecBatch>> batches)
+    : batches(std::move(batches)), ready_fut(Future<>::Make()) {}
+
+ExecNode::ExecNode(ExecPlan* plan, const QueryNode* query_node)
+    : plan_(plan),
+      query_node_(query_node),
+      num_inputs_(query_node->num_inputs()),
+      finished_fut_(Future<>::Make()) {}
+
+ExecNode::~ExecNode() = default;
+
+void ExecNode::ReserveBatches(int32_t num_batches) {
+  // Should be called with mutex locked
+  if (static_cast<size_t>(num_batches) > input_batches_.size()) {
+    input_batches_.resize(num_batches);
+  }
+}
+
+ExecNode::InputBatch* ExecNode::EnsureBatch(int32_t batch_index) {
+  // Should be called with mutex locked
+  if (input_batches_[batch_index] == nullptr) {
+    input_batches_[batch_index].reset(
+        new InputBatch{std::vector<util::optional<compute::ExecBatch>>(num_inputs_)});
+  }
+  return input_batches_[batch_index].get();
+}
+
+Status ExecNode::InputReceived(int32_t input_index, int32_t batch_index,
+                               compute::ExecBatch batch) {
+  auto lock = mutex_.Lock();
+
+  if (input_index >= num_inputs_) {
+    return Status::Invalid("Invalid input index");
+  }
+  if (finish_at_ >= 0 && batch_index >= finish_at_) {
+    return Status::Invalid("Input batch index out of bounds");
+  }
+
+  ReserveBatches(batch_index + 1);
+  auto* input_batch = EnsureBatch(batch_index);
+
+  if (input_batch->batches[input_index].has_value()) {
+    return Status::Invalid("Batch #", batch_index, " for input #", input_index,
+                           " already received");
+  }
+  input_batch->batches[input_index] = std::move(batch);
+  if (++input_batch->num_ready == num_inputs_) {
+    input_batch->ready_fut.MarkFinished();
+  }
+  return Status::OK();
+}
+
+Status ExecNode::InputFinished(int32_t num_batches) {
+  auto lock = mutex_.Lock();
+
+  if (finish_at_ >= 0) {
+    return Status::Invalid("InputFinished already called");
+  }
+  finish_at_ = num_batches;
+  ReserveBatches(num_batches);
+
+  std::vector<Future<>> batch_futures;
+  for (int32_t i = 0; i < num_batches; ++i) {
+    auto* input_batch = EnsureBatch(i);
+    batch_futures[i] = input_batch->ready_fut;
+  }
+
+  // TODO lifetime
+  AllComplete(std::move(batch_futures))
+      .AddCallback([this](const Result<detail::Empty>& res) {
+        finished_fut_.MarkFinished(res.status());
+      });
+  return Status::OK();
+}
+
+Future<> ExecNode::RunAsync(int32_t batch_index, internal::Executor* executor) {
+  auto lock = mutex_.Lock();
+
+  ReserveBatches(batch_index + 1);
+  auto* input_batch = EnsureBatch(batch_index);
+
+  // TODO lifetime (take strong ref to ExecPlan?)
+  return executor->Transfer(input_batch->ready_fut)
+      .Then([this, batch_index](...) -> Status { return RunSyncInternal(batch_index); });
+}
+
+Future<> ExecNode::FinishAsync(internal::Executor* executor) {
+  auto lock = mutex_.Lock();
+
+  // TODO lifetime
+  return executor->Transfer(finished_fut_).Then([this](...) -> Status {
+    return FinishSyncInternal();
+  });
+}
+
+}  // namespace engine
+}  // namespace arrow

cpp/src/arrow/engine/exec_plan.h

@@ -0,0 +1,131 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#pragma once
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "arrow/compute/type_fwd.h"
+#include "arrow/type_fwd.h"
+#include "arrow/util/future.h"
+#include "arrow/util/macros.h"
+#include "arrow/util/mutex.h"
+#include "arrow/util/optional.h"
+#include "arrow/util/type_fwd.h"
+#include "arrow/util/visibility.h"
+
+namespace arrow {
+namespace engine {
+
+class ExecNode;
+class QueryNode;
+class QueryPlan;
+
+class ARROW_EXPORT ExecPlan {
+ public:
+  using NodeVector = std::vector<ExecNode*>;
+
+  virtual ~ExecPlan() = default;
+
+  /// The query plan this ExecPlan is an instance of
+  const QueryPlan& query_plan() const { return *query_plan_; }
+
+  compute::ExecContext* context() { return context_; }
+
+ protected:
+  friend class QueryPlan;
+
+  ExecPlan() = default;
+
+  const std::shared_ptr<const QueryPlan> query_plan_;
+  compute::ExecContext* context_;
+};
+
+class ARROW_EXPORT ExecNode {
+ public:
+  using NodeVector = std::vector<ExecNode*>;
+
+  virtual ~ExecNode();
+
+  /// The query node this ExecNode is an instance of
+  const QueryNode& query_node() const { return *query_node_; }
+
+  /// This node's exec plan
+  ExecPlan* plan() { return plan_; }
+
+  /// Transfer input batch to ExecNode
+  ///
+  /// When all inputs are received for a given batch_index, the batch is ready
+  /// for execution.
+  Status InputReceived(int32_t input_index, int32_t batch_index,
+                       compute::ExecBatch batch);
+
+  /// Mark the inputs finished after the given number of batches.
+  ///
+  /// This may be called before all inputs are received.  This simply fixes
+  /// the total number of incoming batches so that the ExecNode knows when
+  /// it has received all input.
+  Status InputFinished(int32_t num_batches);
+
+  /// Schedule batch execution once all inputs are received for the given batch_index
+  ///
+  /// The returned Future is finished once execution of the batch is finished.
+  /// Note that execution doesn't necessarily mean that any outputs are produced.
+  /// Depending on the ExecNode type, outputs may be produced on the fly,
+  /// or only at the end when all inputs have been received.
+  Future<> RunAsync(int32_t batch_index, internal::Executor* executor);
+
+  /// Schedule finalization once all batches are executed
+  ///
+  /// Return a Future that will be marked finished once all inputs are received
+  /// and all computation has finished.
+  ///
+  /// RunAsync and FinishAsync can be though of as exposing a map/reduce pipeline.
+  Future<> FinishAsync(internal::Executor* executor);
+
+ protected:
+  struct InputBatch {
+    std::vector<util::optional<compute::ExecBatch>> batches;
+    int32_t num_ready = 0;
+    Future<> ready_fut;
+
+    explicit InputBatch(std::vector<util::optional<compute::ExecBatch>> batches);
+  };
+
+  ExecNode(ExecPlan* plan, const QueryNode* query_node);
+
+  virtual Status RunSyncInternal(int32_t batch_index) = 0;
+  virtual Status FinishSyncInternal() = 0;
+
+  InputBatch* EnsureBatch(int32_t batch_index);
+  void ReserveBatches(int32_t num_batches);
+
+  ExecPlan* plan_;
+  const QueryNode* const query_node_;
+  const int32_t num_inputs_;
+
+  // XXX also use a per-input batch mutex?
+  util::Mutex mutex_;
+  std::vector<std::unique_ptr<InputBatch>> input_batches_;
+  int32_t finish_at_ = -1;
+  Future<> finished_fut_;
+};
+
+}  // namespace engine
+}  // namespace arrow