be/src/exec/select-node.h

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#ifndef IMPALA_EXEC_SELECT_NODE_H
#define IMPALA_EXEC_SELECT_NODE_H

#include <boost/scoped_ptr.hpp>

#include "exec/exec-node.h"
#include "runtime/mem-pool.h"
#include <boost/scoped_ptr.hpp>

namespace impala {

class Tuple;
class TupleRow;

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

/// 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 void Codegen(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()
  /////////////////////////////////////////

  typedef void (*CopyRowsFn)(SelectNode*, RowBatch*);
  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);

  /// Codegen CopyRows(). Used for mostly codegen'ing the conjuncts evaluation logic.
  Status CodegenCopyRows(RuntimeState* state);
};

}

#endif