ha_example.h

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/** @file ha_example.h
 
    @brief
  The ha_example engine is a stubbed storage engine for example purposes only;
  it does nothing at this point. Its purpose is to provide a source
  code illustration of how to begin writing new storage engines; see also
  /storage/example/ha_example.cc.
 
    @note
  Please read ha_example.cc before reading this file.
  Reminder: The example storage engine implements all methods that are
  *required* to be implemented. For a full list of all methods that you can
  implement, see handler.h.
 
   @see
  /sql/handler.h and /storage/example/ha_example.cc
*/
 
#include <sys/types.h>
 
#include "my_base.h" /* ha_rows */
#include "my_compiler.h"
#include "my_inttypes.h"
#include "sql/handler.h" /* handler */
#include "thr_lock.h"    /* THR_LOCK, THR_LOCK_DATA */
 
/** @brief
  Example_share is a class that will be shared among all open handlers.
  This example implements the minimum of what you will probably need.
*/
class Example_share : public Handler_share {
 public:
  THR_LOCK lock;
  Example_share();
  ~Example_share() override { thr_lock_delete(&lock); }
};
 
/** @brief
  Class definition for the storage engine
*/
class ha_example : public handler {
  THR_LOCK_DATA lock;          ///< MySQL lock
  Example_share *share;        ///< Shared lock info
  Example_share *get_share();  ///< Get the share
 
 public:
  ha_example(handlerton *hton, TABLE_SHARE *table_arg);
  ~ha_example() override = default;
 
  /** @brief
    The name that will be used for display purposes.
   */
  const char *table_type() const override { return "EXAMPLE"; }
 
  /**
    Replace key algorithm with one supported by SE, return the default key
    algorithm for SE if explicit key algorithm was not provided.
 
    @sa handler::adjust_index_algorithm().
  */
  enum ha_key_alg get_default_index_algorithm() const override {
    return HA_KEY_ALG_HASH;
  }
  bool is_index_algorithm_supported(enum ha_key_alg key_alg) const override {
    return key_alg == HA_KEY_ALG_HASH;
  }
 
  /** @brief
    This is a list of flags that indicate what functionality the storage engine
    implements. The current table flags are documented in handler.h
  */
  ulonglong table_flags() const override {
    /*
      We are saying that this engine is just statement capable to have
      an engine that can only handle statement-based logging. This is
      used in testing.
    */
    return HA_BINLOG_STMT_CAPABLE;
  }
 
  /** @brief
    This is a bitmap of flags that indicates how the storage engine
    implements indexes. The current index flags are documented in
    handler.h. If you do not implement indexes, just return zero here.
 
      @details
    part is the key part to check. First key part is 0.
    If all_parts is set, MySQL wants to know the flags for the combined
    index, up to and including 'part'.
  */
  ulong index_flags(uint inx [[maybe_unused]], uint part [[maybe_unused]],
                    bool all_parts [[maybe_unused]]) const override {
    return 0;
  }
 
  /** @brief
    unireg.cc will call max_supported_record_length(), max_supported_keys(),
    max_supported_key_parts(), uint max_supported_key_length()
    to make sure that the storage engine can handle the data it is about to
    send. Return *real* limits of your storage engine here; MySQL will do
    min(your_limits, MySQL_limits) automatically.
   */
  uint max_supported_record_length() const override {
    return HA_MAX_REC_LENGTH;
  }
 
  /** @brief
    unireg.cc will call this to make sure that the storage engine can handle
    the data it is about to send. Return *real* limits of your storage engine
    here; MySQL will do min(your_limits, MySQL_limits) automatically.
 
      @details
    There is no need to implement ..._key_... methods if your engine doesn't
    support indexes.
   */
  uint max_supported_keys() const override { return 0; }
 
  /** @brief
    unireg.cc will call this to make sure that the storage engine can handle
    the data it is about to send. Return *real* limits of your storage engine
    here; MySQL will do min(your_limits, MySQL_limits) automatically.
 
      @details
    There is no need to implement ..._key_... methods if your engine doesn't
    support indexes.
   */
  uint max_supported_key_parts() const override { return 0; }
 
  /** @brief
    unireg.cc will call this to make sure that the storage engine can handle
    the data it is about to send. Return *real* limits of your storage engine
    here; MySQL will do min(your_limits, MySQL_limits) automatically.
 
      @details
    There is no need to implement ..._key_... methods if your engine doesn't
    support indexes.
   */
  uint max_supported_key_length() const override { return 0; }
 
  /** @brief
    Called in test_quick_select to determine if indexes should be used.
  */
  double scan_time() override {
    return (double)(stats.records + stats.deleted) / 20.0 + 10;
  }
 
  /** @brief
    This method will never be called if you do not implement indexes.
  */
  double read_time(uint, uint, ha_rows rows) override {
    return (double)rows / 20.0 + 1;
  }
 
  /*
    Everything below are methods that we implement in ha_example.cc.
 
    Most of these methods are not obligatory, skip them and
    MySQL will treat them as not implemented
  */
  /** @brief
    We implement this in ha_example.cc; it's a required method.
  */
  int open(const char *name, int mode, uint test_if_locked,
           const dd::Table *table_def) override;  // required
 
  /** @brief
    We implement this in ha_example.cc; it's a required method.
  */
  int close(void) override;  // required
 
  /** @brief
    We implement this in ha_example.cc. It's not an obligatory method;
    skip it and and MySQL will treat it as not implemented.
  */
  int write_row(uchar *buf) override;
 
  /** @brief
    We implement this in ha_example.cc. It's not an obligatory method;
    skip it and and MySQL will treat it as not implemented.
  */
  int update_row(const uchar *old_data, uchar *new_data) override;
 
  /** @brief
    We implement this in ha_example.cc. It's not an obligatory method;
    skip it and and MySQL will treat it as not implemented.
  */
  int delete_row(const uchar *buf) override;
 
  /** @brief
    We implement this in ha_example.cc. It's not an obligatory method;
    skip it and and MySQL will treat it as not implemented.
  */
  int index_read_map(uchar *buf, const uchar *key, key_part_map keypart_map,
                     enum ha_rkey_function find_flag) override;
 
  /** @brief
    We implement this in ha_example.cc. It's not an obligatory method;
    skip it and and MySQL will treat it as not implemented.
  */
  int index_next(uchar *buf) override;
 
  /** @brief
    We implement this in ha_example.cc. It's not an obligatory method;
    skip it and and MySQL will treat it as not implemented.
  */
  int index_prev(uchar *buf) override;
 
  /** @brief
    We implement this in ha_example.cc. It's not an obligatory method;
    skip it and and MySQL will treat it as not implemented.
  */
  int index_first(uchar *buf) override;
 
  /** @brief
    We implement this in ha_example.cc. It's not an obligatory method;
    skip it and and MySQL will treat it as not implemented.
  */
  int index_last(uchar *buf) override;
 
  /** @brief
    Unlike index_init(), rnd_init() can be called two consecutive times
    without rnd_end() in between (it only makes sense if scan=1). In this
    case, the second call should prepare for the new table scan (e.g if
    rnd_init() allocates the cursor, the second call should position the
    cursor to the start of the table; no need to deallocate and allocate
    it again. This is a required method.
  */
  int rnd_init(bool scan) override;  // required
  int rnd_end() override;
  int rnd_next(uchar *buf) override;             ///< required
  int rnd_pos(uchar *buf, uchar *pos) override;  ///< required
  void position(const uchar *record) override;   ///< required
  int info(uint) override;                       ///< required
  int extra(enum ha_extra_function operation) override;
  int external_lock(THD *thd, int lock_type) override;  ///< required
  int delete_all_rows(void) override;
  ha_rows records_in_range(uint inx, key_range *min_key,
                           key_range *max_key) override;
  int delete_table(const char *from, const dd::Table *table_def) override;
  int rename_table(const char *from, const char *to,
                   const dd::Table *from_table_def,
                   dd::Table *to_table_def) override;
  int create(const char *name, TABLE *form, HA_CREATE_INFO *create_info,
             dd::Table *table_def) override;  ///< required
 
  THR_LOCK_DATA **store_lock(
      THD *thd, THR_LOCK_DATA **to,
      enum thr_lock_type lock_type) override;  ///< required
};