Chapter聽16.聽Writing a Custom Storage Engine - MySQL 5.1参考手册中文版

鍦ㄦ墽琛屼换浣曡�诲彇鎴栧啓鎿嶄綔涔嬪墠锛岃皟鐢�store_lock()鍑芥暟銆�

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鍙�鑳界殑閿佸畾绫诲瀷瀹氫箟浜�includes/thr_lock.h涓�锛屽苟鍒楀湪涓嬮潰锛�

enum thr_lock_type

{

         TL_IGNORE=-1,

                    TL_UNLOCK,                             /* UNLOCK ANY LOCK */

                    TL_READ,                                 /* Read lock */

                    TL_READ_WITH_SHARED_LOCKS,  

         TL_READ_HIGH_PRIORITY,      /* High prior. than TL_WRITE. Allow concurrent insert */

         TL_READ_NO_INSERT,                /* READ, Don't allow concurrent insert */

         TL_WRITE_ALLOW_WRITE,                   /*   Write lock, but allow other threads to read / write. */

         TL_WRITE_ALLOW_READ,        /*       Write lock, but allow other threads to read / write. */

         TL_WRITE_CONCURRENT_INSERT, /* WRITE lock used by concurrent insert. */

         TL_WRITE_DELAYED,                 /* Write used by INSERT DELAYED.  Allows READ locks */

         TL_WRITE_LOW_PRIORITY,            /* WRITE lock that has lower priority than TL_READ */

         TL_WRITE,                         /* Normal WRITE lock */

         TL_WRITE_ONLY               /* Abort new lock request with an error */

};  

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THR_LOCK_DATA **ha_tina::store_lock(THD *thd,

                                     THR_LOCK_DATA **to,

                                     enum thr_lock_type lock_type)

 {

   if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK)

     lock.type=lock_type;

   *to++= &lock;

   return to;

 }  

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int ha_example::external_lock(THD *thd, int lock_type)

 {

   DBUG_ENTER("ha_example::external_lock");

   DBUG_RETURN(0);

 }

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  int ha_tina::rnd_init(bool scan)
    {
      DBUG_ENTER("ha_tina::rnd_init");
 
      current_position= next_position= 0;
      records= 0;
      chain_ptr= chain;
 
      DBUG_RETURN(0);
    }  

ulonglong data_file_length;           /* Length off data file */

ulonglong max_data_file_length;       /* Length off data file */

ulonglong index_file_length;

ulonglong max_index_file_length;

ulonglong delete_length;              /* Free bytes */

ulonglong auto_increment_value;

ha_rows records;                      /* Records in table */

ha_rows deleted;                      /* Deleted records */

ulong raid_chunksize;

ulong mean_rec_length;         /* physical reclength */

time_t create_time;                   /* When table was created */

time_t check_time;

time_t update_time;  

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int ha_tina::extra(enum ha_extra_function operation)
 {
   DBUG_ENTER("ha_tina::extra");
   DBUG_RETURN(0);
 }

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int ha_tina::rnd_next(byte *buf)

 {

   DBUG_ENTER("ha_tina::rnd_next");

   statistic_increment(table->in_use->status_var.ha_read_rnd_next_count, &LOCK_status);

   current_position= next_position;

   if (!share->mapped_file)

     DBUG_RETURN(HA_ERR_END_OF_FILE);

   if (HA_ERR_END_OF_FILE == find_current_row(buf) )

     DBUG_RETURN(HA_ERR_END_OF_FILE);

   records++;

   DBUG_RETURN(0);

 }  

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int ha_tina::find_current_row(byte *buf)

 {

   byte *mapped_ptr= (byte *)share->mapped_file + current_position;

   byte *end_ptr;

   DBUG_ENTER("ha_tina::find_current_row");

   /* EOF should be counted as new line */

   if ((end_ptr=  find_eoln(share->mapped_file, current_position,

                            share->file_stat.st_size)) == 0)

     DBUG_RETURN(HA_ERR_END_OF_FILE);

   for (Field **field=table->field ; *field ; field++)

   {

     buffer.length(0);

     mapped_ptr++; // Increment past the first quote

     for(;mapped_ptr != end_ptr; mapped_ptr++)

     {

       // Need to convert line feeds!

       if (*mapped_ptr == '"' &&

           (((mapped_ptr[1] == ',') && (mapped_ptr[2] == '"')) ||

            (mapped_ptr == end_ptr -1 )))

       {

         mapped_ptr += 2; // Move past the , and the "

         break;

       }

       if (*mapped_ptr == '\\' && mapped_ptr != (end_ptr - 1))

       {

         mapped_ptr++;

         if (*mapped_ptr == 'r')

           buffer.append('\r');

         else if (*mapped_ptr == 'n' )

           buffer.append('\n');

         else if ((*mapped_ptr == '\\') || (*mapped_ptr == '"'))

           buffer.append(*mapped_ptr);

         else  /* This could only happed with an externally created file */

         {

           buffer.append('\\');

           buffer.append(*mapped_ptr);

         }

       }

       else

         buffer.append(*mapped_ptr);

     }

     (*field)->store(buffer.ptr(), buffer.length(), system_charset_info);

   }

   next_position= (end_ptr - share->mapped_file)+1;

   /* Maybe use \N for null? */

   memset(buf, 0, table->s->null_bytes); /* We do not implement nulls! */

   DBUG_RETURN(0);

 }  

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static const char *ha_tina_exts[] =
 {
   ".CSV",
   NullS
 };
        
const char **ha_tina::bas_ext() const
 {
   return ha_tina_exts;
 }  

榛樿�ゅ疄鏂�

static const char *ha_example_exts[] = {
   NullS
 };
 
const char **ha_example::bas_ext() const
 {
   return ha_example_exts;
 }

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int ha_example::close(void)
{
  DBUG_ENTER("ha_example::close");
  DBUG_RETURN(free_share(share));
}

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int ha_tina::create(const char *name, TABLE *table_arg,
                    HA_CREATE_INFO *create_info)
{
  char name_buff[FN_REFLEN];
  File create_file;
  DBUG_ENTER("ha_tina::create");

  if ((create_file= my_create(fn_format(name_buff, name, "", ".CSV",
                                        MY_REPLACE_EXT|MY_UNPACK_FILENAME),0,
                              O_RDWR | O_TRUNC,MYF(MY_WME))) < 0)
    DBUG_RETURN(-1);

  my_close(create_file,MYF(0));

  DBUG_RETURN(0);
}          

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{ return 0; }

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{ return 0; }

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::info()鐢ㄤ簬灏嗕俊鎭�杩斿洖缁欎紭鍖栫▼搴忋�傜洰鍓嶏紝璇ヨ〃澶勭悊绋嬪簭鏈�瀹炴柦瀹為檯闇�瑕佺殑澶у�氭暟瀛楁�点��SHOW涔熻兘鍒╃敤璇ユ暟鎹�銆傛敞鎰忥紝鎴栬�镐綘鎵撶畻鍦ㄤ綘鐨勪唬鐮佷腑鍖呭惈涓嬭堪鍐呭�光��if (records > 2) records = 2鈥濄�傚師鍥犲湪浜庯紝鏈嶅姟鍣ㄤ粎浼樺寲鍏锋湁涓�鏉¤�板綍鐨勬儏褰�銆傚�傛灉鍦ㄨ〃鎵�鎻忚繃绋嬩腑锛屼綘涓嶆竻妤氳�板綍鐨勬暟鐩�锛屾渶濂藉皢璁板綍鏁拌�句��2锛屼互渚胯兘澶熻繑鍥炲敖鍙�鑳藉�氱殑鎵�闇�璁板綍銆傞櫎浜嗚�板綍澶栵紝浣犳垨璁歌繕甯屾湜璁剧疆鍏朵粬鍙橀噺锛屽寘鎷�锛氬垹闄ょ殑璁板綍锛�data_file_length锛�index_file_length锛�delete_length锛�check_time銆傛洿澶氫俊鎭�锛岃�峰弬瑙�handler.h涓�鐨勫叕鍏卞彉閲忋��

鍦ㄤ笅杩版枃浠朵腑璋冪敤锛�filesort.cc ha_heap.cc item_sum.cc opt_sum.cc sql_delete.cc sql_delete.cc sql_derived.cc sql_select.cc sql_select.cc sql_select.cc sql_select.cc sql_select.cc sql_show.cc sql_show.cc sql_show.cc sql_show.cc sql_table.cc sql_union.cc sql_update.cc

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void ha_tina::info(uint flag)
{
  DBUG_ENTER("ha_tina::info");
  /* This is a lie, but you don't want the optimizer to see zero or 1 */
  if (records < 2)
    records= 2;
  DBUG_VOID_RETURN;
}          

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鐢�handler::ha_open()浠�handler.cc涓�璋冪敤銆傞�氳繃璋冪敤ha_open()锛岀劧鍚庤皟鐢ㄥ�勭悊绋嬪簭鐩稿叧鐨�open()锛屾湇鍔″櫒鎵撳紑鎵�鏈夎〃銆�

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杩欐槸open鏂规硶銆傝皟鐢�open浠ユ墦寮�鏁版嵁搴撹〃銆�

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        #define HA_OPEN_KEYFILE                 1

        #define HA_OPEN_RNDFILE                 2

        #define HA_GET_INDEX              4

        #define HA_GET_INFO                 8     /* do a ha_info() after open */

        #define HA_READ_ONLY              16    /* File opened as readonly */

        #define HA_TRY_READ_ONLY        32    /* Try readonly if can't open with read and write */

        #define HA_WAIT_IF_LOCKED       64      /* Wait if locked on open */

        #define HA_ABORT_IF_LOCKED    128       /* skip if locked on open.*/

        #define HA_BLOCK_LOCK             256   /* unlock when reading some records */

        #define HA_OPEN_TEMPORARY       512

鏈�鍚庣殑閫夐」瑙勫畾浜嗗湪鎵撳紑琛ㄤ箣鍓嶆槸鍚﹀簲妫�鏌ヨ〃涓婄殑閿佸畾銆�

鍏稿瀷鎯呭喌涓嬶紝瀛樺偍寮曟搸闇�瑕佸疄鐜版煇绉嶅舰寮忕殑鍏变韩璁块棶鎺у埗锛屼互闃叉�㈠�氱嚎绋嬬幆澧冧笅鐨勬枃浠舵崯鍧忋�傚叧浜庡�備綍瀹炵幇鏂囦欢閿佸畾鐨勭ず渚嬶紝璇峰弬瑙�sql/examples/ha_tina.cc鐨�get_share()鍜�free_share()鏂规硶銆�

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        int ha_tina::open(const char *name, int mode, uint test_if_locked)
        {
        DBUG_ENTER("ha_tina::open");
        
        if (!(share= get_share(name, table)))
        DBUG_RETURN(1);
        thr_lock_data_init(&share->lock,&lock,NULL);
        ref_length=sizeof(off_t);
        
        DBUG_RETURN(0);
        }          
      

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涓�index_init()涓嶅悓锛�rnd_init()鍙�浠ヨ皟鐢ㄤ袱娆★紝涓ゆ�¤皟鐢ㄤ箣闂翠笉浣跨敤rnd_end()锛堜粎褰�scan=1鏃舵墠鏈夋剰涔夛級銆傞殢鍚庯紝绗�2娆¤皟鐢ㄥ簲鍑嗗�囧ソ鏂扮殑琛ㄦ壂鎻忋�備緥濡傦紝濡傛灉rnd_init鍒嗛厤浜嗗厜鏍囷紝绗�2娆¤皟鐢ㄥ簲灏嗗厜鏍囧畾浣嶄簬琛ㄧ殑寮�濮嬮儴鍒嗭紝涓嶉渶瑕佹挙閿�鍒嗛厤骞跺啀娆″垎閰嶃��

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int ha_tina::rnd_init(bool scan)
{
  DBUG_ENTER("ha_tina::rnd_init");

  current_position= next_position= 0;
  records= 0;
  chain_ptr= chain;
  DBUG_RETURN(0);
}          

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浠庝笅杩版枃浠惰皟鐢�锛�filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc, 鍜�sql_update.cc銆�

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int ha_archive::rnd_next(byte *buf)
{
  int rc;
  DBUG_ENTER("ha_archive::rnd_next");

  if (share->crashed)
      DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
 
  if (!scan_rows)
    DBUG_RETURN(HA_ERR_END_OF_FILE);
  scan_rows--;

  statistic_increment(table->in_use->status_var.ha_read_rnd_next_count,
		      &LOCK_status);
    current_position= gztell(archive);
  rc= get_row(archive, buf);
 
  if (rc != HA_ERR_END_OF_FILE)
    records++;

  DBUG_RETURN(rc);
}          

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閲婃斁閿佸畾鏃讹紝涔熷皢璋冪敤store_lock()銆傚湪杩欑�嶆儏鍐典笅锛岄�氬父涓嶉渶瑕佷綔浠讳綍浜嬨��

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鐢�get_lock_data()浠�lock.cc涓�璋冪敤銆�

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/* 
  Below is an example of how to setup row level locking.
*/
THR_LOCK_DATA **ha_archive::store_lock(THD *thd,
                                       THR_LOCK_DATA **to,
                                       enum thr_lock_type lock_type)
{
  if (lock_type == TL_WRITE_DELAYED)
    delayed_insert= TRUE;
  else
    delayed_insert= FALSE;

  if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK) 
  {
    /* 
      Here is where we get into the guts of a row level lock.
      If TL_UNLOCK is set 
      If we are not doing a LOCK TABLE or DISCARD/IMPORT
      TABLESPACE, then allow multiple writers 
    */

    if ((lock_type >= TL_WRITE_CONCURRENT_INSERT &&
         lock_type <= TL_WRITE) && !thd->in_lock_tables
        && !thd->tablespace_op)
      lock_type = TL_WRITE_ALLOW_WRITE;

    /* 
      In queries of type INSERT INTO t1 SELECT ... FROM t2 ...
      MySQL would use the lock TL_READ_NO_INSERT on t2, and that
      would conflict with TL_WRITE_ALLOW_WRITE, blocking all inserts
      to t2. Convert the lock to a normal read lock to allow
      concurrent inserts to t2. 
    */

    if (lock_type == TL_READ_NO_INSERT && !thd->in_lock_tables) 
      lock_type = TL_READ;

    lock.type=lock_type;
  }

  *to++= &lock;
 
  return to;
}          

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