be/src/exec/select-node.h

// 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.


#ifndef IMPALA_EXEC_SELECT_NODE_H
#define IMPALA_EXEC_SELECT_NODE_H

#include <boost/scoped_ptr.hpp>

#include "codegen/codegen-fn-ptr.h"
#include "exec/exec-node.h"
#include "runtime/mem-pool.h"

namespace impala {

class SelectNode;
class Tuple;
class TupleRow;

class SelectPlanNode : public PlanNode {
 public:
  virtual Status CreateExecNode(RuntimeState* state, ExecNode** node) const override;
  virtual void Codegen(FragmentState* state) override;

  ~SelectPlanNode(){}

  /// Codegened version of SelectNode::CopyRows().
  typedef void (*CopyRowsFn)(SelectNode*, RowBatch*);
  CodegenFnPtr<CopyRowsFn> codegend_copy_rows_fn_;

 private:
  /// Codegen SelectNode::CopyRows().
  Status CodegenCopyRows(FragmentState* state);
};

/// Node that evaluates conjuncts and enforces a limit but otherwise passes along
/// the rows pulled from its child unchanged.

class SelectNode : public ExecNode {
 public:
  SelectNode(ObjectPool* pool, const SelectPlanNode& pnode, const DescriptorTbl& descs);

  virtual Status Prepare(RuntimeState* state) override;
  virtual Status Open(RuntimeState* state) override;
  virtual Status GetNext(RuntimeState* state, RowBatch* row_batch, bool* eos) override;
  virtual Status Reset(RuntimeState* state, RowBatch* row_batch) override;
  virtual void Close(RuntimeState* state) override;

 private:
  /////////////////////////////////////////
  /// BEGIN: Members that must be Reset()

  /// current row batch of child
  boost::scoped_ptr<RowBatch> child_row_batch_;

  /// index of current row in child_row_batch_
  int child_row_idx_;

  /// true if last GetNext() call on child signalled eos
  bool child_eos_;

  /// END: Members that must be Reset()
  /////////////////////////////////////////

  /// Reference to the codegened function pointer owned by the SelectPlanNode object that
  /// was used to create this instance.
  const CodegenFnPtr<SelectPlanNode::CopyRowsFn>& codegend_copy_rows_fn_;

  /// Copy rows from child_row_batch_ for which conjuncts_ evaluate to true to
  /// output_batch, up to limit_ or till the output row batch reaches capacity.
  void CopyRows(RowBatch* output_batch);
};

}

#endif