table_variables_metadata.h

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/* Copyright (c) 2023, 2024, Oracle and/or its affiliates.
 
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  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
 
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#ifndef TABLE_VARIABLES_METADATA_H
#define TABLE_VARIABLES_METADATA_H
 
/**
  @file storage/perfschema/table_variables_metadata.h
  Table VARIABLES_META (declarations).
*/
 
#include <sys/types.h>
 
#include "my_base.h"
#include "my_inttypes.h"
#include "mysql/components/services/system_variable_source_type.h"
#include "mysql_com.h"
#include "storage/perfschema/pfs_column_types.h"
#include "storage/perfschema/pfs_engine_table.h"
#include "storage/perfschema/pfs_variable.h"
 
class Field;
class Plugin_table;
struct TABLE;
struct THR_LOCK;
 
/**
  Calculated from sys_var::flag_enum
*/
enum enum_variable_scope : int {
  SCOPE_GLOBAL = 1,
  SCOPE_SESSION,
  SCOPE_SESSION_ONLY
};
 
/**
  Calculated from enum_mysql_show_type
*/
enum enum_variable_data_type : int {
  TYPE_INTEGER = 1,
  TYPE_NUMERIC,  // double
  TYPE_STRING,
  TYPE_ENUMERATION,
  TYPE_BOOLEAN,
  TYPE_SET  // set, flagset
};
 
/**
  A row of table
  PERFORMANCE_SCHEMA.VARIABLES_METADATA.
*/
struct row_variables_metadata {
  row_variables_metadata();
  row_variables_metadata(sys_var *system_var);
  row_variables_metadata(const row_variables_metadata &other);
  row_variables_metadata &operator=(const row_variables_metadata &other);
 
  /** Column VARIABLE_NAME. */
  char m_variable_name[COL_OBJECT_NAME_SIZE];
  uint m_variable_name_length;
  /** Column VARIABLE_SCOPE. */
  enum_variable_scope m_variable_scope;
  /** Column DATA_TYPE. */
  enum_variable_data_type m_variable_data_type;
  /** Column MIN_VALUE. */
  char m_min_value[COL_OBJECT_NAME_SIZE];
  uint m_min_value_length;
  /** Column MAX_VALUE. */
  char m_max_value[COL_OBJECT_NAME_SIZE];
  uint m_max_value_length;
  /** Column DOCUMENTATION. */
  char m_documentation[COL_INFO_SIZE];
  uint m_documentation_length;
};
 
/** Table PERFORMANCE_SCHEMA.VARIABLES_METADATA. */
class table_variables_metadata : public PFS_engine_table {
  typedef PFS_simple_index pos_t;
  typedef Prealloced_array<row_variables_metadata, SYSTEM_VARIABLE_PREALLOC>
      Variable_array;
 
 public:
  /** Table share */
  static PFS_engine_table_share m_share;
  static PFS_engine_table *create(PFS_engine_table_share *);
  static ha_rows get_row_count();
 
  int rnd_init(bool scan) override;
  int rnd_next() override;
  int rnd_pos(const void *pos) override;
  void reset_position() override;
 
 protected:
  int read_row_values(TABLE *table, unsigned char *buf, Field **fields,
                      bool read_all) override;
  table_variables_metadata();
 
 public:
  ~table_variables_metadata() override = default;
 
 protected:
  /* Build sys_var tracker array. */
  bool init_sys_var_array();
  /* Build sys_var info cache. */
  int do_materialize_all();
 
  int make_row(const row_variables_metadata &row);
 
 private:
  /** Table share lock. */
  static THR_LOCK m_table_lock;
  /** Table definition. */
  static Plugin_table m_table_def;
 
  /* True when system variable descriptors array is complete. */
  bool m_initialized;
  /* Array of system variable descriptors. */
  System_variable_tracker::Array m_sys_var_tracker_array;
  /* Cache of materialized variables. */
  Variable_array m_cache;
  /* True when cache is complete. */
  bool m_materialized;
  /* Version of global hash/array. Changes when vars added/removed. */
  ulonglong m_version;
 
  /** Current row. */
  row_variables_metadata m_row;
  /** Current position. */
  pos_t m_pos;
  /** Next position. */
  pos_t m_next_pos;
};
 
#endif