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A fix of the fix for BUG#1209 (was: SELECT DATABASE() still shows dropped database).

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Don't free the client's selected db (thd->db) when it has been DROPped,
if this is a slave thread; the x_free() was causing a lot
of various bugs in rpl_loaddata_rule_m (garbage characters, segfault, hangs in
other threads).
A small post-merge fix (rli->inside_transaction exists in 4.0 only).


sql/log_event.cc:
  Post-merge fix (rli->inside_transaction existed in 4.0 only)
sql/sql_db.cc:
  Don't free the client's selected db (thd->db) when it has been DROPped,
  if this is a slave thread; the x_free() was causing a lot
  of various bugs in rpl_loaddata_rule_m which does a DROP DATABASE 
  (garbage characters, segfault, hangs in other threads).
This commit is contained in:
unknown 2003-09-26 22:56:13 +02:00
parent 2d7beead44
commit 44f65c246d
2 changed files with 31 additions and 6 deletions
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11
sql/log_event.cc
View file

@ -1876,19 +1876,22 @@ int Rotate_log_event::exec_event(struct st_relay_log_info* rli)
pthread_mutex_lock(&rli->data_lock);
#ifdef TO_BE_CHECKED_BY_GUILHEM
if (rli->inside_transaction)
if (thd->options & OPTION_BEGIN)
{
slave_print_error(rli, 0,
opt_using_transactions ?
"\
There is an unfinished transaction in the relay log (could find neither \
COMMIT nor ROLLBACK in the relay log); It could be that the master died while \
writing the transaction to its binary log. Now the slave is rolling back the \
transaction.");
transaction." :
"\
There is an unfinished transaction in the relay log (could find neither \
COMMIT nor ROLLBACK in the relay log); It could be that the master died while \
writing the transaction to its binary log.");
pthread_mutex_unlock(&rli->data_lock);
DBUG_RETURN(1);
}
#endif
memcpy(log_name, new_log_ident, ident_len+1);
rli->notify_group_master_log_name_update();

26
sql/sql_db.cc
View file

@ -391,10 +391,32 @@ int mysql_rm_db(THD *thd,char *db,bool if_exists, bool silent)
exit:
start_waiting_global_read_lock(thd);
/*
If this database was the client's selected database, we silently change the
client's selected database to nothing (to have an empty SELECT DATABASE() in
the future). For this we free() thd->db and set it to 0. But we don't do
free() for the slave thread. Indeed, doing a x_free() on it leads to nasty
problems (i.e. long painful debugging) because in this thread, thd->db is
the same as data_buf and db of the Query_log_event which is dropping the
database. So if you free() thd->db, you're freeing data_buf. You set thd->db
to 0 but not data_buf (thd->db and data_buf are two distinct pointers which
point to the same place). Then in ~Query_log_event(), we have
'if (data_buf) free(data_buf)'
data_buf is !=0 so this makes a DOUBLE free().
Side effects of this double free() are, randomly (depends on the machine),
when the slave is replicating a DROP DATABASE:
- garbage characters in the error message:
"Error 'Can't drop database 'test2'; database doesn't exist' on query
'h4zI¿'"
- segfault
- hang in "free(vio)" (yes!) in the I/O or SQL slave threads (so slave
server hangs at shutdown etc).
*/
if (thd->db && !strcmp(thd->db, db))
{
x_free(thd->db);
thd->db= 0;
if (!(thd->slave_thread)) /* a slave thread will free it itself */
x_free(thd->db);
thd->db= 0;
}
exit2:
VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));