memo.h

/* Copyright (c) 2021 OceanBase and/or its affiliates. All rights reserved.
miniob is licensed under Mulan PSL v2.
You can use this software according to the terms and conditions of the Mulan PSL v2.
You may obtain a copy of Mulan PSL v2 at:
         http://license.coscl.org.cn/MulanPSL2
THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
See the Mulan PSL v2 for more details. */
 
#pragma once
 
#include "common/lang/unordered_set.h"
#include "common/lang/vector.h"
#include "common/lang/memory.h"
#include "common/log/log.h"
#include "sql/optimizer/cascade/group_expr.h"
#include "sql/optimizer/cascade/group.h"
 
const int UNDEFINED_GROUP = -1;
 
class Memo
{
public:
  Memo() = default;
 
  ~Memo() = default;
 
  GroupExpr *insert_expression(GroupExpr *gexpr) { return insert_expression(gexpr, -1); }
 
  GroupExpr *insert_expression(GroupExpr *gexpr, int target_group);
 
  Group *get_group_by_id(int id) const
  {
    auto idx = id;
    ASSERT(idx >= 0 && static_cast<size_t>(idx) < groups_.size(), "group_id out of bounds");
    return groups_[idx].get();
  }
 
  void dump() const;
 
  void record_operator(unique_ptr<OperatorNode> &&node) { operator_nodes_.emplace(node.get(), std::move(node)); }
 
  void release_operator(OperatorNode *node)
  {
    auto it = operator_nodes_.find(node);
    if (it != operator_nodes_.end()) {
      it->second.release();
    }
  }
 
private:
  int add_new_group(GroupExpr *gexpr);
 
  struct GExprPtrHash
  {
    std::size_t operator()(GroupExpr *const &s) const
    {
      if (s == nullptr)
        return 0;
      return s->hash();
    }
  };
 
  struct GExprPtrEq
  {
    bool operator()(GroupExpr *t1, GroupExpr *t2) const
    {
      if (t1 && t2) {  // 确保非空检查
        return (*t1 == *t2);
      }
      return false;  // 防止空指针解引用
    }
  };
 
  std::unordered_set<GroupExpr *, GExprPtrHash, GExprPtrEq> group_expressions_;
 
  vector<unique_ptr<Group>> groups_;
 
  // TODO: 这是用来存储在 optimize
  // 过程中生成的临时物理算子节点的，有些物理算子节点的所有权会转移到外面，有些物理算子的所有权还在memo，需要删除。 用
  // shared_ptr 更加合适，但是改动比较大，先暂时不改了。
  std::unordered_map<OperatorNode *, unique_ptr<OperatorNode>> operator_nodes_;
};