core/sql/generator/vegrewritepairs.h

#ifndef VEGREWRITEPAIRS_H
#define VEGREWRITEPAIRS_H
/* -*-C++-*-
 *****************************************************************************
 *
 * File:         vegrewritepairs.h
 * Description:  
 *               
 *               
 * Created:      12/19/96
 * Language:     C++
 * Code location: GenPreCode.C
 *
 *
// @@@ START COPYRIGHT @@@
//
// 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.
//
// @@@ END COPYRIGHT @@@
 *
 *
 *****************************************************************************
 */

// -----------------------------------------------------------------------

#include "ValueDesc.h"
#include "NABasicObject.h"

// ---- Class VEGRewritePairs
// This class is a helper class whose claim to life is help
// prevent that a VEGPredicate is rewritten twice during
// the rewrite of predicates in the preCodeGene phase.
// It bahaves as a map of <ValueId, ValueId> pairs
// The left ValueId represents the value of a VEG predicate
// that was rewritten and the right value id is the value
// of the rewritten pred.
// To use this class, check for the existence of the VEGPredicate
// to be rewritten in the left sides of the pairs inside the
// collection. If it is there, don't rewrite but grab the
// right hand side and return that. If it's not there,
// rewrite as usual.

class VEGRewritePairs : public NABasicObject {

public:
  VEGRewritePairs(CollHeap* heap);

  ~VEGRewritePairs();

  static ULng32 valueIdHashFunc(const CollIndex &v);

  // ----------------
  // -- Accesors:
  // ----------------

  // Returns TRUE if original is already in the collection, if so
  // rewritten contains the rewritten id obtained when original
  // was rewritten
  NABoolean getRewritten(ValueId& rewritten, const ValueId& original) const;
  

  void print( FILE* ofd = stdout,
	      const char* indent = DEFAULT_INDENT,
	      const char* title = "VEGRewritePairs") const;

  
  // ----------------
  // --- Mutators: 
  // ----------------
  
  void insert(const ValueId& original,
	      const ValueId& rewritten);

  void clear()
  {
    CollIndex *key;
    VEGRewritePair *value;
    NAHashDictionaryIterator<CollIndex, VEGRewritePair> iter(vegRewritePairs_);

    for (CollIndex i=0; i < iter.entries(); i++) {
      iter.getNext(key, value);
      NADELETEBASIC(key, heap_);
      delete value;
    }
    vegRewritePairs_.clear();
  }


  // private:    the oss build fails when this is uncommented

  class VEGRewritePair : public NABasicObject {

  public:
    
    VEGRewritePair(const ValueId& original, const ValueId& rewritten):
	 original_(original),
	 rewritten_(rewritten)
    {
    }

    // ----------------
    // -- Accesors:
    // ----------------

    const ValueId& getOriginal() const
    { return original_;}

    const ValueId& getRewritten() const
    { return rewritten_;}

    void print( FILE* ofd = stdout) const;

    NABoolean operator == (const VEGRewritePair & other) 
    { 
      return original_ == other.original_ && rewritten_ == other.rewritten_;
    }
    
  private:
    ValueId original_, // predicate before rewrite
      rewritten_; // predicate after rewrite
  };

private:

  const VEGRewritePairs::VEGRewritePair *
  getPair(const ValueId& original) const;
  
  CollHeap *heap_;
  NAHashDictionary<CollIndex, VEGRewritePair> vegRewritePairs_;

}; //VEGRewritePairs

#endif
// eof