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BUG#46364 MyISAM transbuffer problems (NTM problem)

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It is well-known that due to concurrency issues, a slave can become
inconsistent when a transaction contains updates to both transaction and
non-transactional tables.
                    
In a nutshell, the current code-base tries to preserve causality among the
statements by writing non-transactional statements to the txn-cache which
is flushed upon commit. However, modifications done to non-transactional
tables on behalf of a transaction become immediately visible to other
connections but may not immediately get into the binary log and therefore
consistency may be broken.
            
In general, it is impossible to automatically detect causality/dependency
among statements by just analyzing the statements sent to the server. This
happen because dependency may be hidden in the application code and it is
necessary to know a priori all the statements processed in the context of
a transaction such as in a procedure. Moreover, even for the few cases that
we could automatically address in the server, the computation effort
required could make the approach infeasible.
            
So, in this patch we introduce the option
      - "--binlog-direct-non-transactional-updates" that can be used to bypass
      the current behavior in order to write directly to binary log statements
      that change non-transactional tables.

Besides, it is used to enable the WL#2687 which is disabled by default.
This commit is contained in:
Alfranio Correia
2010-01-21 13:10:34 +00:00
parent 32d17f7daa
commit 8da3fea266
32 changed files with 962 additions and 297 deletions
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42
sql/sys_vars.cc
View File

@ -299,6 +299,48 @@ static Sys_var_enum Sys_binlog_format(
NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(binlog_format_check),
ON_UPDATE(fix_binlog_format_after_update));
static bool binlog_direct_check(sys_var *self, THD *thd, set_var *var)
{
/*
Makes the session variable 'binlog_direct_non_transactional_updates'
read-only inside a transaction.
*/
if (thd->active_transaction() && (var->type == OPT_SESSION))
{
my_error(ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_BINLOG_DIRECT, MYF(0));
return 1;
}
/*
Makes the session variable 'binlog_direct_non_transactional_updates'
read-only if within a procedure, trigger or function.
*/
if (thd->in_sub_stmt)
{
my_error(ER_STORED_FUNCTION_PREVENTS_SWITCH_BINLOG_DIRECT, MYF(0));
return 1;
}
if (check_has_super(self, thd, var))
return true;
if (var->type == OPT_GLOBAL ||
(thd->variables.binlog_direct_non_trans_update ==
var->save_result.ulonglong_value))
return false;
return false;
}
static Sys_var_mybool Sys_binlog_direct(
"binlog_direct_non_transactional_updates",
"Causes updates to non-transactional engines using statement format to "
"be written directly to binary log. Before using this option make sure "
"that there are no dependencies between transactional and "
"non-transactional tables such as in the statement INSERT INTO t_myisam "
"SELECT * FROM t_innodb; otherwise, slaves may diverge from the master.",
SESSION_VAR(binlog_direct_non_trans_update),
CMD_LINE(OPT_ARG), DEFAULT(FALSE),
NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(binlog_direct_check));
static Sys_var_ulong Sys_bulk_insert_buff_size(
"bulk_insert_buffer_size", "Size of tree cache used in bulk "
"insert optimisation. Note that this is a limit per thread!",