~drizzle-trunk/drizzle/development

/* Copyright (C) 2000-2003 MySQL AB

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; version 2 of the License.

   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 for more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, write to the Free Software

   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

#include "mysql_priv.h"

#include "rpl_mi.h"

#include "rpl_rli.h"

#include "sql_repl.h"  // For check_binlog_magic

#include "rpl_utility.h"

static int32_t count_relay_log_space(Relay_log_info* rli);

// Defined in slave.cc

int32_t init_intvar_from_file(int32_t* var, IO_CACHE* f, int32_t default_val);

int32_t init_strvar_from_file(char *var, int32_t max_size, IO_CACHE *f,

			  const char *default_val);

Relay_log_info::Relay_log_info()

  :Slave_reporting_capability("SQL"),

   no_storage(false), replicate_same_server_id(::replicate_same_server_id),

   info_fd(-1), cur_log_fd(-1), save_temporary_tables(0),

#if defined(HAVE_purify) && HAVE_purify

   is_fake(false),

#endif

   cur_log_old_open_count(0), group_relay_log_pos(0), event_relay_log_pos(0),

   group_master_log_pos(0), log_space_total(0), ignore_log_space_limit(0),

   last_master_timestamp(0), slave_skip_counter(0),

   abort_pos_wait(0), slave_run_id(0), sql_thd(0),

   inited(0), abort_slave(0), slave_running(0), until_condition(UNTIL_NONE),

   until_log_pos(0), retried_trans(0),

   tables_to_lock(0), tables_to_lock_count(0),

   last_event_start_time(0), m_flags(0)

{

  group_relay_log_name[0]= event_relay_log_name[0]=

    group_master_log_name[0]= 0;

  until_log_name[0]= ign_master_log_name_end[0]= 0;

  memset((char*) &info_file, 0, sizeof(info_file));

  memset((char*) &cache_buf, 0, sizeof(cache_buf));

  cached_charset_invalidate();

  pthread_mutex_init(&run_lock, MY_MUTEX_INIT_FAST);

  pthread_mutex_init(&data_lock, MY_MUTEX_INIT_FAST);

  pthread_mutex_init(&log_space_lock, MY_MUTEX_INIT_FAST);

  pthread_cond_init(&data_cond, NULL);

  pthread_cond_init(&start_cond, NULL);

  pthread_cond_init(&stop_cond, NULL);

  pthread_cond_init(&log_space_cond, NULL);

  relay_log.init_pthread_objects();

  return;

}

Relay_log_info::~Relay_log_info()

{

  pthread_mutex_destroy(&run_lock);

  pthread_mutex_destroy(&data_lock);

  pthread_mutex_destroy(&log_space_lock);

  pthread_cond_destroy(&data_cond);

  pthread_cond_destroy(&start_cond);

  pthread_cond_destroy(&stop_cond);

  pthread_cond_destroy(&log_space_cond);

  relay_log.cleanup();

  return;

}

int32_t init_relay_log_info(Relay_log_info* rli,

			const char* info_fname)

{

  char fname[FN_REFLEN+128];

  int32_t info_fd;

  const char* msg = 0;

  int32_t error = 0;

  assert(!rli->no_storage);         // Don't init if there is no storage

  if (rli->inited)                       // Set if this function called

    return(0);

  fn_format(fname, info_fname, mysql_data_home, "", 4+32);

  pthread_mutex_lock(&rli->data_lock);

  info_fd = rli->info_fd;

  rli->cur_log_fd = -1;

  rli->slave_skip_counter=0;

  rli->abort_pos_wait=0;

  rli->log_space_limit= relay_log_space_limit;

  rli->log_space_total= 0;

  rli->tables_to_lock= 0;

  rli->tables_to_lock_count= 0;

  /*

    The relay log will now be opened, as a SEQ_READ_APPEND IO_CACHE.

    Note that the I/O thread flushes it to disk after writing every

    event, in flush_master_info(mi, 1).

  */

  /*

    For the maximum log size, we choose max_relay_log_size if it is

    non-zero, max_binlog_size otherwise. If later the user does SET

    GLOBAL on one of these variables, fix_max_binlog_size and

    fix_max_relay_log_size will reconsider the choice (for example

    if the user changes max_relay_log_size to zero, we have to

    switch to using max_binlog_size for the relay log) and update

    rli->relay_log.max_size (and mysql_bin_log.max_size).

  */

  {

    char buf[FN_REFLEN];

    const char *ln;

    static bool name_warning_sent= 0;

    ln= rli->relay_log.generate_name(opt_relay_logname, "-relay-bin",

                                     1, buf);

    /* We send the warning only at startup, not after every RESET SLAVE */

    if (!opt_relay_logname && !opt_relaylog_index_name && !name_warning_sent)

    {

      /*

        User didn't give us info to name the relay log index file.

        Picking `hostname`-relay-bin.index like we do, causes replication to

        fail if this slave's hostname is changed later. So, we would like to

        instead require a name. But as we don't want to break many existing

        setups, we only give warning, not error.

      */

      sql_print_warning("Neither --relay-log nor --relay-log-index were used;"

                        " so replication "

                        "may break when this MySQL server acts as a "

                        "slave and has his hostname changed!! Please "

                        "use '--relay-log=%s' to avoid this problem.", ln);

      name_warning_sent= 1;

    }

    /*

      note, that if open() fails, we'll still have index file open

      but a destructor will take care of that

    */

    if (rli->relay_log.open_index_file(opt_relaylog_index_name, ln) ||

        rli->relay_log.open(ln, LOG_BIN, 0, SEQ_READ_APPEND, 0,

                            (max_relay_log_size ? max_relay_log_size :

                            max_binlog_size), 1))

    {

      pthread_mutex_unlock(&rli->data_lock);

      sql_print_error("Failed in open_log() called from init_relay_log_info()");

      return(1);

    }

  }

  /* if file does not exist */

  if (access(fname,F_OK))

  {

    /*

      If someone removed the file from underneath our feet, just close

      the old descriptor and re-create the old file

    */

    if (info_fd >= 0)

      my_close(info_fd, MYF(MY_WME));

    if ((info_fd = my_open(fname, O_CREAT|O_RDWR|O_BINARY, MYF(MY_WME))) < 0)

    {

      sql_print_error("Failed to create a new relay log info file (\

file '%s', errno %d)", fname, my_errno);

      msg= current_thd->main_da.message();

      goto err;

    }

    if (init_io_cache(&rli->info_file, info_fd, IO_SIZE*2, READ_CACHE, 0L,0,

                      MYF(MY_WME)))

    {

      sql_print_error("Failed to create a cache on relay log info file '%s'",

                      fname);

      msg= current_thd->main_da.message();

      goto err;

    }

    /* Init relay log with first entry in the relay index file */

    if (init_relay_log_pos(rli,NullS,BIN_LOG_HEADER_SIZE,0 /* no data lock */,

                           &msg, 0))

    {

      sql_print_error("Failed to open the relay log 'FIRST' (relay_log_pos 4)");

      goto err;

    }

    rli->group_master_log_name[0]= 0;

    rli->group_master_log_pos= 0;

    rli->info_fd= info_fd;

  }

  else // file exists

  {

    if (info_fd >= 0)

      reinit_io_cache(&rli->info_file, READ_CACHE, 0L,0,0);

    else

    {

      int32_t error=0;

      if ((info_fd = my_open(fname, O_RDWR|O_BINARY, MYF(MY_WME))) < 0)

      {

        sql_print_error("\

Failed to open the existing relay log info file '%s' (errno %d)",

                        fname, my_errno);

        error= 1;

      }

      else if (init_io_cache(&rli->info_file, info_fd,

                             IO_SIZE*2, READ_CACHE, 0L, 0, MYF(MY_WME)))

      {

        sql_print_error("Failed to create a cache on relay log info file '%s'",

                        fname);

        error= 1;

      }

      if (error)

      {

        if (info_fd >= 0)

          my_close(info_fd, MYF(0));

        rli->info_fd= -1;

        rli->relay_log.close(LOG_CLOSE_INDEX | LOG_CLOSE_STOP_EVENT);

        pthread_mutex_unlock(&rli->data_lock);

        return(1);

      }

    }

    rli->info_fd = info_fd;

    int32_t relay_log_pos, master_log_pos;

    if (init_strvar_from_file(rli->group_relay_log_name,

                              sizeof(rli->group_relay_log_name),

                              &rli->info_file, "") ||

       init_intvar_from_file(&relay_log_pos,

                             &rli->info_file, BIN_LOG_HEADER_SIZE) ||

       init_strvar_from_file(rli->group_master_log_name,

                             sizeof(rli->group_master_log_name),

                             &rli->info_file, "") ||

       init_intvar_from_file(&master_log_pos, &rli->info_file, 0))

    {

      msg="Error reading slave log configuration";

      goto err;

    }

    strmake(rli->event_relay_log_name,rli->group_relay_log_name,

            sizeof(rli->event_relay_log_name)-1);

    rli->group_relay_log_pos= rli->event_relay_log_pos= relay_log_pos;

    rli->group_master_log_pos= master_log_pos;

    if (init_relay_log_pos(rli,

                           rli->group_relay_log_name,

                           rli->group_relay_log_pos,

                           0 /* no data lock*/,

                           &msg, 0))

    {

      char llbuf[22];

      sql_print_error("Failed to open the relay log '%s' (relay_log_pos %s)",

                      rli->group_relay_log_name,

                      llstr(rli->group_relay_log_pos, llbuf));

      goto err;

    }

  }

  assert(rli->event_relay_log_pos >= BIN_LOG_HEADER_SIZE);

  assert(my_b_tell(rli->cur_log) == rli->event_relay_log_pos);

  /*

    Now change the cache from READ to WRITE - must do this

    before flush_relay_log_info

  */

  reinit_io_cache(&rli->info_file, WRITE_CACHE,0L,0,1);

  if ((error= flush_relay_log_info(rli)))

    sql_print_error("Failed to flush relay log info file");

  if (count_relay_log_space(rli))

  {

    msg="Error counting relay log space";

    goto err;

  }

  rli->inited= 1;

  pthread_mutex_unlock(&rli->data_lock);

  return(error);

err:

  sql_print_error(msg);

  end_io_cache(&rli->info_file);

  if (info_fd >= 0)

    my_close(info_fd, MYF(0));

  rli->info_fd= -1;

  rli->relay_log.close(LOG_CLOSE_INDEX | LOG_CLOSE_STOP_EVENT);

  pthread_mutex_unlock(&rli->data_lock);

  return(1);

}

static inline int32_t add_relay_log(Relay_log_info* rli,LOG_INFO* linfo)

{

  struct stat s;

  if (stat(linfo->log_file_name,&s))

  {

    sql_print_error("log %s listed in the index, but failed to stat",

                    linfo->log_file_name);

    return(1);

  }

  rli->log_space_total += s.st_size;

  return(0);

}

static int32_t count_relay_log_space(Relay_log_info* rli)

{

  LOG_INFO linfo;

  rli->log_space_total= 0;

  if (rli->relay_log.find_log_pos(&linfo, NullS, 1))

  {

    sql_print_error("Could not find first log while counting relay log space");

    return(1);

  }

  do

  {

    if (add_relay_log(rli,&linfo))

      return(1);

  } while (!rli->relay_log.find_next_log(&linfo, 1));

  /*

     As we have counted everything, including what may have written in a

     preceding write, we must reset bytes_written, or we may count some space

     twice.

  */

  rli->relay_log.reset_bytes_written();

  return(0);

}

/*

   Reset UNTIL condition for Relay_log_info

   SYNOPSYS

    clear_until_condition()

      rli - Relay_log_info structure where UNTIL condition should be reset

 */

void Relay_log_info::clear_until_condition()

{

  until_condition= Relay_log_info::UNTIL_NONE;

  until_log_name[0]= 0;

  until_log_pos= 0;

  return;

}

/*

  Open the given relay log

  SYNOPSIS

    init_relay_log_pos()

    rli                 Relay information (will be initialized)

    log                 Name of relay log file to read from. NULL = First log

    pos                 Position in relay log file

    need_data_lock      Set to 1 if this functions should do mutex locks

    errmsg              Store pointer to error message here

    look_for_description_event

                        1 if we should look for such an event. We only need

                        this when the SQL thread starts and opens an existing

                        relay log and has to execute it (possibly from an

                        offset >4); then we need to read the first event of

                        the relay log to be able to parse the events we have

                        to execute.

  DESCRIPTION

  - Close old open relay log files.

  - If we are using the same relay log as the running IO-thread, then set

    rli->cur_log to point to the same IO_CACHE entry.

  - If not, open the 'log' binary file.

  TODO

    - check proper initialization of group_master_log_name/group_master_log_pos

  RETURN VALUES

    0   ok

    1   error.  errmsg is set to point to the error message

*/

int32_t init_relay_log_pos(Relay_log_info* rli,const char* log,

                       uint64_t pos, bool need_data_lock,

                       const char** errmsg,

                       bool look_for_description_event)

{

  *errmsg=0;

  pthread_mutex_t *log_lock=rli->relay_log.get_log_lock();

  if (need_data_lock)

    pthread_mutex_lock(&rli->data_lock);

  /*

    Slave threads are not the only users of init_relay_log_pos(). CHANGE MASTER

    is, too, and init_slave() too; these 2 functions allocate a description

    event in init_relay_log_pos, which is not freed by the terminating SQL slave

    thread as that thread is not started by these functions. So we have to free

    the description_event here, in case, so that there is no memory leak in

    running, say, CHANGE MASTER.

  */

  delete rli->relay_log.description_event_for_exec;

  /*

    By default the relay log is in binlog format 3 (4.0).

    Even if format is 4, this will work enough to read the first event

    (Format_desc) (remember that format 4 is just lenghtened compared to format

    3; format 3 is a prefix of format 4).

  */

  rli->relay_log.description_event_for_exec= new

    Format_description_log_event(3);

  pthread_mutex_lock(log_lock);

  /* Close log file and free buffers if it's already open */

  if (rli->cur_log_fd >= 0)

  {

    end_io_cache(&rli->cache_buf);

    my_close(rli->cur_log_fd, MYF(MY_WME));

    rli->cur_log_fd = -1;

  }

  rli->group_relay_log_pos = rli->event_relay_log_pos = pos;

  /*

    Test to see if the previous run was with the skip of purging

    If yes, we do not purge when we restart

  */

  if (rli->relay_log.find_log_pos(&rli->linfo, NullS, 1))

  {

    *errmsg="Could not find first log during relay log initialization";

    goto err;

  }

  if (log && rli->relay_log.find_log_pos(&rli->linfo, log, 1))

  {

    *errmsg="Could not find target log during relay log initialization";

    goto err;

  }

  strmake(rli->group_relay_log_name,rli->linfo.log_file_name,

          sizeof(rli->group_relay_log_name)-1);

  strmake(rli->event_relay_log_name,rli->linfo.log_file_name,

          sizeof(rli->event_relay_log_name)-1);

  if (rli->relay_log.is_active(rli->linfo.log_file_name))

  {

    /*

      The IO thread is using this log file.

      In this case, we will use the same IO_CACHE pointer to

      read data as the IO thread is using to write data.

    */

    my_b_seek((rli->cur_log=rli->relay_log.get_log_file()), (off_t)0);

    if (check_binlog_magic(rli->cur_log,errmsg))

      goto err;

    rli->cur_log_old_open_count=rli->relay_log.get_open_count();

  }

  else

  {

    /*

      Open the relay log and set rli->cur_log to point at this one

    */

    if ((rli->cur_log_fd=open_binlog(&rli->cache_buf,

                                     rli->linfo.log_file_name,errmsg)) < 0)

      goto err;

    rli->cur_log = &rli->cache_buf;

  }

  /*

    In all cases, check_binlog_magic() has been called so we're at offset 4 for

    sure.

  */

  if (pos > BIN_LOG_HEADER_SIZE) /* If pos<=4, we stay at 4 */

  {

    Log_event* ev;

    while (look_for_description_event)

    {

      /*

        Read the possible Format_description_log_event; if position

        was 4, no need, it will be read naturally.

      */

      if (my_b_tell(rli->cur_log) >= pos)

        break;

      /*

        Because of we have rli->data_lock and log_lock, we can safely read an

        event

      */

      if (!(ev=Log_event::read_log_event(rli->cur_log,0,

                                         rli->relay_log.description_event_for_exec)))

      {

        if (rli->cur_log->error) /* not EOF */

        {

          *errmsg= "I/O error reading event at position 4";

          goto err;

        }

        break;

      }

      else if (ev->get_type_code() == FORMAT_DESCRIPTION_EVENT)

      {

        delete rli->relay_log.description_event_for_exec;

        rli->relay_log.description_event_for_exec= (Format_description_log_event*) ev;

        /*

          As ev was returned by read_log_event, it has passed is_valid(), so

          my_malloc() in ctor worked, no need to check again.

        */

        /*

          Ok, we found a Format_description event. But it is not sure that this

          describes the whole relay log; indeed, one can have this sequence

          (starting from position 4):

          Format_desc (of slave)

          Rotate (of master)

          Format_desc (of master)

          So the Format_desc which really describes the rest of the relay log

          is the 3rd event (it can't be further than that, because we rotate

          the relay log when we queue a Rotate event from the master).

          But what describes the Rotate is the first Format_desc.

          So what we do is:

          go on searching for Format_description events, until you exceed the

          position (argument 'pos') or until you find another event than Rotate

          or Format_desc.

        */

      }

      else

      {

        look_for_description_event= (ev->get_type_code() == ROTATE_EVENT);

        delete ev;

      }

    }

    my_b_seek(rli->cur_log,(off_t)pos);

  }

err:

  /*

    If we don't purge, we can't honour relay_log_space_limit ;

    silently discard it

  */

  if (!relay_log_purge)

    rli->log_space_limit= 0;

  pthread_cond_broadcast(&rli->data_cond);

  pthread_mutex_unlock(log_lock);

  if (need_data_lock)

    pthread_mutex_unlock(&rli->data_lock);

  if (!rli->relay_log.description_event_for_exec->is_valid() && !*errmsg)

    *errmsg= "Invalid Format_description log event; could be out of memory";

  return ((*errmsg) ? 1 : 0);

}

/*

  Waits until the SQL thread reaches (has executed up to) the

  log/position or timed out.

  SYNOPSIS

    wait_for_pos()

    thd             client thread that sent SELECT MASTER_POS_WAIT

    log_name        log name to wait for

    log_pos         position to wait for

    timeout         timeout in seconds before giving up waiting

  NOTES

    timeout is int64_t whereas it should be uint32_t ; but this is

    to catch if the user submitted a negative timeout.

  RETURN VALUES

    -2          improper arguments (log_pos<0)

                or slave not running, or master info changed

                during the function's execution,

                or client thread killed. -2 is translated to NULL by caller

    -1          timed out

    >=0         number of log events the function had to wait

                before reaching the desired log/position

 */

int32_t Relay_log_info::wait_for_pos(THD* thd, String* log_name,

                                    int64_t log_pos,

                                    int64_t timeout)

{

  int32_t event_count = 0;

  uint32_t init_abort_pos_wait;

  int32_t error=0;

  struct timespec abstime; // for timeout checking

  const char *msg;

  if (!inited)

    return(-2);

  set_timespec(abstime,timeout);

  pthread_mutex_lock(&data_lock);

  msg= thd->enter_cond(&data_cond, &data_lock,

                       "Waiting for the slave SQL thread to "

                       "advance position");

  /*

     This function will abort when it notices that some CHANGE MASTER or

     RESET MASTER has changed the master info.

     To catch this, these commands modify abort_pos_wait ; We just monitor

     abort_pos_wait and see if it has changed.

     Why do we have this mechanism instead of simply monitoring slave_running

     in the loop (we do this too), as CHANGE MASTER/RESET SLAVE require that

     the SQL thread be stopped?

     This is becasue if someones does:

     STOP SLAVE;CHANGE MASTER/RESET SLAVE; START SLAVE;

     the change may happen very quickly and we may not notice that

     slave_running briefly switches between 1/0/1.

  */

  init_abort_pos_wait= abort_pos_wait;

  /*

    We'll need to

    handle all possible log names comparisons (e.g. 999 vs 1000).

    We use uint32_t for string->number conversion ; this is no

    stronger limitation than in find_uniq_filename in sql/log.cc

  */

  uint32_t log_name_extension;

  char log_name_tmp[FN_REFLEN]; //make a char[] from String

  strmake(log_name_tmp, log_name->ptr(), min(log_name->length(), FN_REFLEN-1));

  char *p= fn_ext(log_name_tmp);

  char *p_end;

  if (!*p || log_pos<0)

  {

    error= -2; //means improper arguments

    goto err;

  }

  // Convert 0-3 to 4

  log_pos= max(log_pos, BIN_LOG_HEADER_SIZE);

  /* p points to '.' */

  log_name_extension= strtoul(++p, &p_end, 10);

  /*

    p_end points to the first invalid character.

    If it equals to p, no digits were found, error.

    If it contains '\0' it means conversion went ok.

  */

  if (p_end==p || *p_end)

  {

    error= -2;

    goto err;

  }

  /* The "compare and wait" main loop */

  while (!thd->killed &&

         init_abort_pos_wait == abort_pos_wait &&

         slave_running)

  {

    bool pos_reached;

    int32_t cmp_result= 0;

    /*

      group_master_log_name can be "", if we are just after a fresh

      replication start or after a CHANGE MASTER TO MASTER_HOST/PORT

      (before we have executed one Rotate event from the master) or

      (rare) if the user is doing a weird slave setup (see next

      paragraph).  If group_master_log_name is "", we assume we don't

      have enough info to do the comparison yet, so we just wait until

      more data. In this case master_log_pos is always 0 except if

      somebody (wrongly) sets this slave to be a slave of itself

      without using --replicate-same-server-id (an unsupported

      configuration which does nothing), then group_master_log_pos

      will grow and group_master_log_name will stay "".

    */

    if (*group_master_log_name)

    {

      char *basename= (group_master_log_name +

                       dirname_length(group_master_log_name));

      /*

        First compare the parts before the extension.

        Find the dot in the master's log basename,

        and protect against user's input error :

        if the names do not match up to '.' included, return error

      */

      char *q= (char*)(fn_ext(basename)+1);

      if (strncmp(basename, log_name_tmp, (int32_t)(q-basename)))

      {

        error= -2;

        break;

      }

      // Now compare extensions.

      char *q_end;

      uint32_t group_master_log_name_extension= strtoul(q, &q_end, 10);

      if (group_master_log_name_extension < log_name_extension)

        cmp_result= -1 ;

      else

        cmp_result= (group_master_log_name_extension > log_name_extension) ? 1 : 0 ;

      pos_reached= ((!cmp_result && group_master_log_pos >= (uint64_t)log_pos) ||

                    cmp_result > 0);

      if (pos_reached || thd->killed)

        break;

    }

    //wait for master update, with optional timeout.

    /*

      We are going to pthread_cond_(timed)wait(); if the SQL thread stops it

      will wake us up.

    */

    if (timeout > 0)

    {

      /*

        Note that pthread_cond_timedwait checks for the timeout

        before for the condition ; i.e. it returns ETIMEDOUT

        if the system time equals or exceeds the time specified by abstime

        before the condition variable is signaled or broadcast, _or_ if

        the absolute time specified by abstime has already passed at the time

        of the call.

        For that reason, pthread_cond_timedwait will do the "timeoutting" job

        even if its condition is always immediately signaled (case of a loaded

        master).

      */

      error=pthread_cond_timedwait(&data_cond, &data_lock, &abstime);

    }

    else

      pthread_cond_wait(&data_cond, &data_lock);

    if (error == ETIMEDOUT || error == ETIME)

    {

      error= -1;

      break;

    }

    error=0;

    event_count++;

  }

err:

  thd->exit_cond(msg);

  if (thd->killed || init_abort_pos_wait != abort_pos_wait ||

      !slave_running)

  {

    error= -2;

  }

  return( error ? error : event_count );

}

void Relay_log_info::inc_group_relay_log_pos(uint64_t log_pos,

                                                bool skip_lock)

{

  if (!skip_lock)

    pthread_mutex_lock(&data_lock);

  inc_event_relay_log_pos();

  group_relay_log_pos= event_relay_log_pos;

  strmake(group_relay_log_name,event_relay_log_name,

          sizeof(group_relay_log_name)-1);

  notify_group_relay_log_name_update();

  /*

    If the slave does not support transactions and replicates a transaction,

    users should not trust group_master_log_pos (which they can display with

    SHOW SLAVE STATUS or read from relay-log.info), because to compute

    group_master_log_pos the slave relies on log_pos stored in the master's

    binlog, but if we are in a master's transaction these positions are always

    the BEGIN's one (excepted for the COMMIT), so group_master_log_pos does

    not advance as it should on the non-transactional slave (it advances by

    big leaps, whereas it should advance by small leaps).

  */

  /*

    In 4.x we used the event's len to compute the positions here. This is

    wrong if the event was 3.23/4.0 and has been converted to 5.0, because

    then the event's len is not what is was in the master's binlog, so this

    will make a wrong group_master_log_pos (yes it's a bug in 3.23->4.0

    replication: Exec_master_log_pos is wrong). Only way to solve this is to

    have the original offset of the end of the event the relay log. This is

    what we do in 5.0: log_pos has become "end_log_pos" (because the real use

    of log_pos in 4.0 was to compute the end_log_pos; so better to store

    end_log_pos instead of begin_log_pos.

    If we had not done this fix here, the problem would also have appeared

    when the slave and master are 5.0 but with different event length (for

    example the slave is more recent than the master and features the event

    UID). It would give false MASTER_POS_WAIT, false Exec_master_log_pos in

    SHOW SLAVE STATUS, and so the user would do some CHANGE MASTER using this

    value which would lead to badly broken replication.

    Even the relay_log_pos will be corrupted in this case, because the len is

    the relay log is not "val".

    With the end_log_pos solution, we avoid computations involving lengthes.

  */

  if (log_pos) // 3.23 binlogs don't have log_posx

  {

    group_master_log_pos= log_pos;

  }

  pthread_cond_broadcast(&data_cond);

  if (!skip_lock)

    pthread_mutex_unlock(&data_lock);

  return;

}

void Relay_log_info::close_temporary_tables()

{

  TABLE *table,*next;

  for (table=save_temporary_tables ; table ; table=next)

  {

    next=table->next;

    /*

      Don't ask for disk deletion. For now, anyway they will be deleted when

      slave restarts, but it is a better intention to not delete them.

    */

    close_temporary(table, 1, 0);

  }

  save_temporary_tables= 0;

  slave_open_temp_tables= 0;

  return;

}

/*

  purge_relay_logs()

  NOTES

    Assumes to have a run lock on rli and that no slave thread are running.

*/

int32_t purge_relay_logs(Relay_log_info* rli, THD *thd, bool just_reset,