topn-node.h

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// Copyright 2012 Cloudera Inc.
//
// 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.


#ifndef IMPALA_EXEC_TOPN_NODE_H
#define IMPALA_EXEC_TOPN_NODE_H

#include <queue>
#include <boost/scoped_ptr.hpp>

#include "exec/exec-node.h"
#include "exec/sort-exec-exprs.h"
#include "runtime/descriptors.h"  // for TupleId
#include "util/tuple-row-compare.h"

namespace impala {

class MemPool;
class RuntimeState;
class Tuple;

class TopNNode : public ExecNode {
 public:
  TopNNode(ObjectPool* pool, const TPlanNode& tnode, const DescriptorTbl& descs);

  virtual Status Init(const TPlanNode& tnode);
  virtual Status Prepare(RuntimeState* state);
  virtual Status Open(RuntimeState* state);
  virtual Status GetNext(RuntimeState* state, RowBatch* row_batch, bool* eos);
  virtual Status Reset(RuntimeState* state);
  virtual void Close(RuntimeState* state);

 protected:
  virtual void DebugString(int indentation_level, std::stringstream* out) const;

 private:

  friend class TupleLessThan;

  void InsertTupleRow(TupleRow* tuple_row);

  void PrepareForOutput();

  int64_t offset_;
  int64_t num_rows_skipped_;

  SortExecExprs sort_exec_exprs_;
  std::vector<bool> is_asc_order_;
  std::vector<bool> nulls_first_;
  TupleDescriptor* materialized_tuple_desc_;

  boost::scoped_ptr<TupleRowComparator> tuple_row_less_than_;

  boost::scoped_ptr<
      std::priority_queue<Tuple*, std::vector<Tuple*>, TupleRowComparator> >
          priority_queue_;

  std::vector<Tuple*> sorted_top_n_;
  std::vector<Tuple*>::iterator get_next_iter_;

  boost::scoped_ptr<MemPool> tuple_pool_;
  Tuple* tmp_tuple_;
};

};

#endif