opt_explain_json.h

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/* Copyright (c) 2011, 2024, Oracle and/or its affiliates.
 
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#ifndef OPT_EXPLAIN_FORMAT_JSON_INCLUDED
#define OPT_EXPLAIN_FORMAT_JSON_INCLUDED
 
#include "sql/opt_explain_format.h"
#include "sql/parse_tree_node_base.h"
 
class Query_result;
class Query_expression;
 
namespace opt_explain_json_namespace {
class context;
}
 
/**
  Formatter class for EXPLAIN FORMAT=JSON output
*/
 
class Explain_format_JSON : public Explain_format {
 public:
  explicit Explain_format_JSON(
      std::optional<std::string_view> explain_into_variable_name)
      : Explain_format(explain_into_variable_name), current_context(nullptr) {}
 
  bool is_hierarchical() const override { return true; }
 
  /// Format versions newer than Linear are always going to be iterator-based.
  bool is_iterator_based(THD *explain_thd, const THD *query_thd) const override;
 
  bool send_headers(Query_result *result) override;
  bool begin_context(enum_parsing_context context, Query_expression *subquery,
                     const Explain_format_flags *flags) override;
  bool end_context(enum_parsing_context context) override;
  bool flush_entry() override { return false; }
  qep_row *entry() override;
 
  /* Convert Json object to string */
  std::string ExplainJsonToString(Json_object *json) override;
 
 private:
  opt_explain_json_namespace::context *current_context;  ///< current tree node
};
 
#endif  // OPT_EXPLAIN_FORMAT_JSON_INCLUDED