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/* 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 */
/**
@file
@brief
logging of commands
@todo
Abort logging when we get an error in reading or writing log files
*/
#include <drizzled/server_includes.h>
#include <drizzled/replicator.h>
#include <mysys/hash.h>
#include <mysys/my_dir.h>
#include <stdarg.h>
#include <drizzled/plugin.h>
#include <drizzled/error.h>
#include <drizzled/errmsg_print.h>
#include <drizzled/gettext.h>
#include <drizzled/data_home.h>
#include <drizzled/session.h>
#include <drizzled/handler.h>
#include <string>
using namespace std;
static const string engine_name("binlog");
StorageEngine *binlog_engine= NULL;
/*
Save position of binary log transaction cache.
SYNPOSIS
binlog_trans_log_savepos()
session The thread to take the binlog data from
pos Pointer to variable where the position will be stored
DESCRIPTION
Save the current position in the binary log transaction cache into
the variable pointed to by 'pos'
*/
static void
binlog_trans_log_savepos(Session *, my_off_t *pos)
{
assert(pos != NULL);
return;
}
class BinlogEngine : public StorageEngine
{
public:
BinlogEngine(const string &name_arg)
: StorageEngine(name_arg,
HTON_NOT_USER_SELECTABLE | HTON_HIDDEN,
sizeof(my_off_t)) {}
virtual int close_connection(Session *)
{
return 0;
}
virtual int prepare(Session *session, bool)
{
/*
do nothing.
just pretend we can do 2pc, so that MySQL won't
switch to 1pc.
real work will be done in DRIZZLE_BIN_LOG::log_xid()
*/
(void)replicator_prepare(session);
return 0;
}
/**
This function is called once after each statement.
It has the responsibility to flush the transaction cache to the
binlog file on commits.
@param engine The binlog StorageEngine.
@param session The client thread that executes the transaction.
@param all This is @c true if this is a real transaction commit, and
@false otherwise.
@see StorageEngine::commit
*/
virtual int commit(Session *session, bool all)
{
/*
Decision table for committing a transaction. The top part, the
*conditions* represent different cases that can occur, and hte
bottom part, the *actions*, represent what should be done in that
particular case.
Real transaction 'all' was true
Statement in cache There were at least one statement in the
transaction cache
In transaction We are inside a transaction
Stmt modified non-trans The statement being committed modified a
non-transactional table
All modified non-trans Some statement before this one in the
transaction modified a non-transactional
table
============================= = = = = = = = = = = = = = = = =
Real transaction N N N N N N N N N N N N N N N N
Statement in cache N N N N N N N N Y Y Y Y Y Y Y Y
In transaction N N N N Y Y Y Y N N N N Y Y Y Y
Stmt modified non-trans N N Y Y N N Y Y N N Y Y N N Y Y
All modified non-trans N Y N Y N Y N Y N Y N Y N Y N Y
Action: (C)ommit/(A)ccumulate C C - C A C - C - - - - A A - A
============================= = = = = = = = = = = = = = = = =
============================= = = = = = = = = = = = = = = = =
Real transaction Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y
Statement in cache N N N N N N N N Y Y Y Y Y Y Y Y
In transaction N N N N Y Y Y Y N N N N Y Y Y Y
Stmt modified non-trans N N Y Y N N Y Y N N Y Y N N Y Y
All modified non-trans N Y N Y N Y N Y N Y N Y N Y N Y
(C)ommit/(A)ccumulate/(-) - - - - C C - C - - - - C C - C
============================= = = = = = = = = = = = = = = = =
In other words, we commit the transaction if and only if both of
the following are true:
- We are not in a transaction and committing a statement
- We are in a transaction and one (or more) of the following are
true:
- A full transaction is committed
OR
- A non-transactional statement is committed and there is
no statement cached
Otherwise, we accumulate the statement
*/
if (all || (!session_test_options(session, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN)))
{
return replicator_end_transaction(session, all, true);
}
return(0);
}
/**
This function is called when a transaction involving a transactional
table is rolled back.
It has the responsibility to flush the transaction cache to the
binlog file. However, if the transaction does not involve
non-transactional tables, nothing needs to be logged.
@param engine The binlog StorageEngine.
@param session The client thread that executes the transaction.
@param all This is @c true if this is a real transaction rollback, and
@false otherwise.
@see StorageEngine::rollback
*/
virtual int rollback(Session *session, bool all)
{
int error=0;
/* TODO: Fix return type */
(void)replicator_end_transaction(session, all, false);
return(error);
}
/**
@note
How do we handle this (unlikely but legal) case:
@verbatim
[transaction] + [update to non-trans table] + [rollback to savepoint] ?
@endverbatim
The problem occurs when a savepoint is before the update to the
non-transactional table. Then when there's a rollback to the savepoint, if we
simply truncate the binlog cache, we lose the part of the binlog cache where
the update is. If we want to not lose it, we need to write the SAVEPOINT
command and the ROLLBACK TO SAVEPOINT command to the binlog cache. The latter
is easy: it's just write at the end of the binlog cache, but the former
should be *inserted* to the place where the user called SAVEPOINT. The
solution is that when the user calls SAVEPOINT, we write it to the binlog
cache (so no need to later insert it). As transactions are never intermixed
in the binary log (i.e. they are serialized), we won't have conflicts with
savepoint names when using mysqlbinlog or in the slave SQL thread.
Then when ROLLBACK TO SAVEPOINT is called, if we updated some
non-transactional table, we don't truncate the binlog cache but instead write
ROLLBACK TO SAVEPOINT to it; otherwise we truncate the binlog cache (which
will chop the SAVEPOINT command from the binlog cache, which is good as in
that case there is no need to have it in the binlog).
*/
virtual int savepoint_set_hook(Session *session, void *sv)
{
bool error;
binlog_trans_log_savepos(session, (my_off_t*) sv);
/* Write it to the binary log */
error= replicator_statement(session, session->query, session->query_length);
return(error);
}
virtual int savepoint_rollback_hook(Session *session, void *)
{
bool error;
error= replicator_statement(session, session->query, session->query_length);
return error;
}
virtual handler* create(TABLE_SHARE*, MEM_ROOT*)
{
return NULL;
}
};
/*
this function is mostly a placeholder.
conceptually, binlog initialization (now mostly done in DRIZZLE_BIN_LOG::open)
should be moved here.
*/
int binlog_init(void *p)
{
StorageEngine** engine= static_cast<StorageEngine **>(p);
if (binlog_engine == NULL)
{
binlog_engine= new BinlogEngine(engine_name);
}
*engine= binlog_engine;
return 0;
}
drizzle_declare_plugin(binlog)
{
DRIZZLE_STORAGE_ENGINE_PLUGIN,
"binlog",
"1.0",
"MySQL AB",
"This is a pseudo storage engine to represent the binlog in a transaction",
PLUGIN_LICENSE_GPL,
binlog_init, /* Plugin Init */
NULL, /* Plugin Deinit */
NULL, /* status variables */
NULL, /* system variables */
NULL /* config options */
}
drizzle_declare_plugin_end;
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