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Filename : opt_trace_context.h
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#ifndef OPT_TRACE_CONTEXT_INCLUDED
#define OPT_TRACE_CONTEXT_INCLUDED

#include "sql_array.h"

class Opt_trace_context;
struct Opt_trace_info;
class Json_writer;

class Opt_trace_stmt {
 public:
  /**
     Constructor, starts a trace for information_schema and dbug.
     @param  ctx_arg          context
  */
  Opt_trace_stmt(Opt_trace_context *ctx_arg);
  ~Opt_trace_stmt();
  void set_query(const char *query_ptr, size_t length, const CHARSET_INFO *charset);
  void open_struct(const char *key, char opening_bracket);
  void close_struct(const char *saved_key, char closing_bracket);
  void fill_info(Opt_trace_info* info);
  void add(const char *key, char *opening_bracket, size_t val_length);
  Json_writer* get_current_json() {return current_json;}
  void missing_privilege();
  void disable_tracing_for_children();
  void enable_tracing_for_children();
  bool is_enabled()
  {
   return I_S_disabled == 0;
  }
  void set_allowed_mem_size(size_t mem_size);
  size_t get_length();
  size_t get_truncated_bytes();
  bool get_missing_priv() { return missing_priv; }

private:
  Opt_trace_context *ctx;
  String query;  // store the query sent by the user
  Json_writer *current_json; // stores the trace
  bool missing_priv;  ///< whether user lacks privilege to see this trace
  /*
    0 <=> this trace should be in information_schema.
  !=0 tracing is disabled, this currently happens when we want to trace a
      sub-statement. For now traces are only collect for the top statement
      not for the sub-statments.
  */
  uint I_S_disabled;
};


class Opt_trace_context
{
public:
   Opt_trace_context();
  ~Opt_trace_context();

  void start(THD *thd, TABLE_LIST *tbl,
             enum enum_sql_command sql_command,
             const char *query,
             size_t query_length,
             const CHARSET_INFO *query_charset,
             ulong max_mem_size_arg);
  void end();
  void set_query(const char *query, size_t length, const CHARSET_INFO *charset);
  void delete_traces();
  void set_allowed_mem_size(size_t mem_size);
  size_t remaining_mem_size();

private:
  Opt_trace_stmt* top_trace()
  {
    return *(traces.front());
  }

public:

  /*
    This returns the top trace from the list of traces. This function
    is used when we want to see the contents of the INFORMATION_SCHEMA.OPTIMIZER_TRACE
  table.
  */

  Opt_trace_stmt* get_top_trace()
  {
    if (!traces.elements())
      return NULL;
    return top_trace();
  }

  /*
    This returns the current trace, to which we are still writing and has not been finished
  */

  Json_writer* get_current_json()
  {
    if (!is_started())
      return NULL;
    return current_trace->get_current_json();
  }

  bool empty()
  {
    return static_cast<uint>(traces.elements()) == 0;
  }

  bool is_started()
  {
    return current_trace && current_trace->is_enabled();
  }

  bool disable_tracing_if_required();

  bool enable_tracing_if_required();

  bool is_enabled();

  void missing_privilege();

  static const char *flag_names[];
  enum
  {
    FLAG_DEFAULT = 0,
    FLAG_ENABLED = 1 << 0
  };

private:
  /*
    List of traces (currently it stores only 1 trace)
  */
  Dynamic_array<Opt_trace_stmt*> traces;
  Opt_trace_stmt *current_trace;
  size_t max_mem_size;
};

#endif /* OPT_TRACE_CONTEXT_INCLUDED */