opt_explain_traditional.h

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/* Copyright (c) 2011, 2023, Oracle and/or its affiliates.
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.
 
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   This program is distributed in the hope that it will be useful,
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License, version 2.0, for more details.
 
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   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
#ifndef OPT_EXPLAIN_FORMAT_TRADITIONAL_INCLUDED
#define OPT_EXPLAIN_FORMAT_TRADITIONAL_INCLUDED
 
#include <assert.h>
// assert
#include <memory>
#include <string>
#include <vector>
 
#include "sql/opt_explain_format.h"
#include "sql/parse_tree_node_base.h"
 
class Item;
class Json_dom;
class Json_object;
class Query_result;
class Query_expression;
template <class T>
class mem_root_deque;
 
/**
  Formatter for the traditional EXPLAIN output
*/
 
class Explain_format_traditional : public Explain_format {
  class Item_null *nil;
  qep_row column_buffer;  ///< buffer for the current output row
 
 public:
  Explain_format_traditional() : nil(nullptr) {}
 
  bool is_hierarchical() const override { return false; }
  bool send_headers(Query_result *result) override;
  bool begin_context(enum_parsing_context, Query_expression *,
                     const Explain_format_flags *) override {
    return false;
  }
  bool end_context(enum_parsing_context) override { return false; }
  bool flush_entry() override;
  qep_row *entry() override { return &column_buffer; }
 
 private:
  bool push_select_type(mem_root_deque<Item *> *items);
};
 
class Explain_format_tree : public Explain_format {
 public:
  Explain_format_tree() = default;
 
  bool is_hierarchical() const override { return false; }
  bool send_headers(Query_result *) override {
    assert(false);
    return true;
  }
  bool begin_context(enum_parsing_context, Query_expression *,
                     const Explain_format_flags *) override {
    assert(false);
    return true;
  }
  bool end_context(enum_parsing_context) override {
    assert(false);
    return true;
  }
  bool flush_entry() override {
    assert(false);
    return true;
  }
  qep_row *entry() override {
    assert(false);
    return nullptr;
  }
  bool is_iterator_based() const override { return true; }
 
  /* Convert Json object to string */
  std::string ExplainJsonToString(Json_object *json) override;
  void ExplainPrintTreeNode(const Json_dom *json, int level,
                            std::string *explain,
                            std::vector<std::string> *tokens_for_force_subplan);
 
 private:
  bool push_select_type(mem_root_deque<Item *> *items);
 
  void AppendChildren(const Json_dom *children, int level, std::string *explain,
                      std::vector<std::string> *tokens_for_force_subplan,
                      std::string *child_token_digest);
  void ExplainPrintCosts(const Json_object *obj, std::string *explain);
};
 
#endif  // OPT_EXPLAIN_FORMAT_TRADITIONAL_INCLUDED