rpl_sys_key_access.h

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/* Copyright (c) 2020, 2025, 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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   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
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   the program or referenced in the documentation.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License, version 2.0, for more details.
 
   You should have received a copy of the GNU General Public License
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   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
#ifndef RPL_SYS_KEY_ACCESS_INCLUDED
#define RPL_SYS_KEY_ACCESS_INCLUDED
 
#include "sql/table.h"
 
/**
  @class Rpl_sys_table_access
 
  The class are wrappers for handler index and random scan functions to
  simplify their usage.
*/
class Rpl_sys_key_access {
 public:
  /* Index type */
  enum class enum_key_type {
    /* Read next row via random scan using handler::ha_rnd_next. */
    RND_NEXT,
    /* Read row via random scan from position using handler::ha_rnd_pos. */
    RND_POS,
    /*
      Read [part of] row via [part of] index using
      handler::ha_index_read_map.
    */
    INDEX_NEXT_SAME,
    /* Read all rows of index using handler::ha_index_first. */
    INDEX_NEXT
  };
 
  /**
    Construction.
  */
  Rpl_sys_key_access() = default;
 
  /**
    Destruction.
    Closes all initialized index or random scan during destruction.
  */
  ~Rpl_sys_key_access();
 
  /**
    Construction.
 
    @param[in]  table     Table object from which row needs to be fetched.
    @param[in]  type      The type of scan to use to read row.
 
    @retval 0     Success
    @retval !0    Error
  */
  int init(TABLE *table, enum_key_type type);
 
  /**
    When index type enum_key_type::INDEX_NEXT_SAME needs to be used to read
    [part of] row via [part of] index.
 
    @param[in]  table       Table object from which row needs to be fetched.
    @param[in]  index       Index to use
    @param[in]  sorted      Use sorted order
    @param[in]  keypart_map Which part of key to use
    @param[in]  find_flag   Direction/condition on key usage
 
    @retval 0     Success
    @retval !0    Error
  */
  int init(TABLE *table, uint index = 0, bool sorted = true,
           key_part_map keypart_map = 1,
           enum ha_rkey_function find_flag = HA_READ_KEY_EXACT);
 
  /**
    When index type enum_key_type::RND_POS needs to be used to read row via
    random scan from position.
 
    @param[in]  table   Table object from which row needs to be fetched.
    @param[in]  pos     The position from where to read row.
 
    @retval 0     Success
    @retval !0    Error
  */
  int init(TABLE *table, const std::string &pos);
 
  /**
    Closes all initialized index or random scan during destruction.
 
    @retval true  if there is error
    @retval false if there is no error
  */
  bool deinit();
 
  /**
    Get next row in the table.
 
    @retval 0     Success
    @retval !0    Error
  */
  int next();
 
  /**
    Verify if error is set, ignores HA_ERR_END_OF_FILE and
    HA_ERR_KEY_NOT_FOUND.
 
    @retval true  if there is error
    @retval false if there is no error
  */
  bool is_read_error();
 
  /**
    Get error set during index initialization or fetching next rows.
 
    @retval 0     Success
    @retval !0    Error
  */
  int get_error() { return m_error; }
 
 private:
  /* TABLE object */
  TABLE *m_table{nullptr};
 
  /* The type of index used */
  enum_key_type m_key_type{enum_key_type::RND_POS};
 
  /* Determine if index is initialized. */
  bool m_key_init{false};
 
  /* Determine if index is deinitialized. */
  bool m_key_deinit{false};
 
  /* The buffer to store the key */
  uchar m_key[MAX_KEY_LENGTH];
 
  /*
    The variable stores error during index initialization or fetching next
    rows.
  */
  int m_error{1};
};
#endif /* RPL_SYS_KEY_ACCESS_INCLUDED */