Summary
=======
With FULL_NODUP mode, before image inclues all columns and after
image inclues only the changed columns. flashback will swap the
value of changed columns from after image to before image.
For example:
BI: c1, c2, c3_old, c4_old
AI: c3_new, c4_new
flashback will reconstruct the before and after images to
BI: c1, c2, c3_new, c4_new
AI: c3_old, c4_old
Implementation
==============
When parsing the before and after image, position and length of
the fields are collected into ai_fields and bi_fields, if it is an
Update_rows_event and the after image doesn't includes all columns.
The changed fields are swapped between bi_fields and ai_fields.
Then it recreates the before image and after image by using
bi_fields and ai_fields. nullbit will be set to 1 if the
field is NULL, otherwise nullbit will be 0.
It also optimized flashback a little bit.
- calc_row_event_length is used instead of print_verbose_one_row
- swap_buff1 and swap_buff2 are removed.
The binlog.flashback test tries to run using the stmt and mix
binlog_format combinations (because it includes have_log_bin.inc),
yet are meaningless tests because the server starts with the
--flashback option, forcing binlog_format=row.
This patch optimizes test time by removing the stmt and mix format
combinations from running.
Reviewed By:
============
Andrei Elkin <andrei.elkin@mariadb.com>
Commit a923d6f49c disabled numeric setting
of character_set_* variables with non-default values:
MariaDB [(none)]> set character_set_client=224;
ERROR 1115 (42000): Unknown character set: '224'
However the corresponding binlog functionality still write numeric
values for log event, and this will break binlog replay if the value is
not default. Now make the server use 'String' type for
'character_set_client' when generating binlog events
Before:
/*!\C utf8mb4 *//*!*/;
SET @@session.character_set_client=224,@@session.collation_connection=224,@@session.collation_server=33/*!*/;
After:
/*!\C utf8mb4 *//*!*/;
SET @@session.character_set_client=utf8mb4,@@session.collation_connection=33,@@session.collation_server=8/*!*/;
Note: prior to the previous commit, setting with '224' or '45' or
'utf8mb4' have the same effect, as they all set the parameter to
'utf8mb4'.
All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer Amazon Web
Services, Inc.
- Major rewrite of ddl_log.cc and ddl_log.h
- ddl_log.cc described in the beginning how the recovery works.
- ddl_log.log has unique signature and is dynamic. It's easy to
add more information to the header and other ddl blocks while still
being able to execute old ddl entries.
- IO_SIZE for ddl blocks is now dynamic. Can be changed without affecting
recovery of old logs.
- Code is more modular and is now usable outside of partition handling.
- Renamed log file to dll_recovery.log and added option --log-ddl-recovery
to allow one to specify the path & filename.
- Added ddl_log_entry_phase[], number of phases for each DDL action,
which allowed me to greatly simply set_global_from_ddl_log_entry()
- Changed how strings are stored in log entries, which allows us to
store much more information in a log entry.
- ddl log is now always created at start and deleted on normal shutdown.
This simplices things notable.
- Added probes debug_crash_here() and debug_simulate_error() to simply
crash testing and allow crash after a given number of times a probe
is executed. See comments in debug_sync.cc and rename_table.test for
how this can be used.
- Reverting failed table and view renames is done trough the ddl log.
This ensures that the ddl log is tested also outside of recovery.
- Added helper function 'handler::needs_lower_case_filenames()'
- Extend binary log with Q_XID events. ddl log handling is using this
to check if a ddl log entry was logged to the binary log (if yes,
it will be deleted from the log during ddl_log_close_binlogged_events()
- If a DDL entry fails 3 time, disable it. This is to ensure that if
we have a crash in ddl recovery code the server will not get stuck
in a forever crash-restart-crash loop.
mysqltest.cc changes:
- --die will now replace $variables with their values
- $error will contain the error of the last failed statement
storage engine changes:
- maria_rename() was changed to be more robust against crashes during
rename.
This allows one to run the test suite even if any of the following
options are changed:
- character-set-server
- collation-server
- join-cache-level
- log-basename
- max-allowed-packet
- optimizer-switch
- query-cache-size and query-cache-type
- skip-name-resolve
- table-definition-cache
- table-open-cache
- Some innodb options
etc
Changes:
- Don't print out the value of system variables as one can't depend on
them to being constants.
- Don't set global variables to 'default' as the default may not
be the same as the test was started with if there was an additional
option file. Instead save original value and reset it at end of test.
- Test that depends on the latin1 character set should include
default_charset.inc or set the character set to latin1
- Test that depends on the original optimizer switch, should include
default_optimizer_switch.inc
- Test that depends on the value of a specific system variable should
set it in the test (like optimizer_use_condition_selectivity)
- Split subselect3.test into subselect3.test and subselect3.inc to
make it easier to set and reset system variables.
- Added .opt files for test that required specfic options that could
be changed by external configuration files.
- Fixed result files in rockdsb & tokudb that had not been updated for
a while.
Problem:
========
The mysqlbinlog tool is leaking memory, causing failures in various tests when
compiling and testing with AddressSanitizer or LeakSanitizer like this:
cmake -DCMAKE_BUILD_TYPE=Debug -DWITH_ASAN:BOOL=ON /path/to/source
make -j$(nproc)
cd mysql-test
ASAN_OPTIONS=abort_on_error=1 ./mtr --parallel=auto
Analysis:
=========
Two types of leaks were observed during above execution.
1) Leak in Log_event::read_log_event(char const*, unsigned int, char const**,
Format_description_log_event const*, char)
File: sql/log_event.cc:2150
For all row based replication events the memory which is allocated during
read_log_event is not freed after the event is processed. The event specific
memory has to be retained only when flashback option is enabled with
mysqlbinlog tool. In this case all the events are retained till the end
statement is received and they are processed in reverse order and they are
destroyed. But in the existing code all events are retained irrespective of
flashback mode. Hence the memory leaks are observed.
2) read_remote_annotate_event(unsigned char*, unsigned long, char const**)
File: client/mysqlbinlog.cc:194
In general the Annotate event is not printed immediately because all
subsequent rbr-events can be filtered away. Instead it will be printed
together with the first not filtered away Table map or the last rbr will be
processed. While reading remote annotate events memory is allocated for event
buffer and event's temp_buf is made to point to the allocated buffer as shown
below. The TRUE flag is used for doing proper cleanup using free_temp_buf().
i.e at the time of deletion of annotate event its destructor takes care of
clearing the temp_buf.
/*
Ensure the event->temp_buf is pointing to the allocated buffer.
(TRUE = free temp_buf on the event deletion)
*/
event->register_temp_buf((char*)event_buf, TRUE);
But existing code does the following when it receives a remote annotate_event.
if (remote_opt)
ev->temp_buf= 0;
That is code immediately sets temp_buf=0, because of which free_temp_buf()
call will return empty handed as it has lost the reference to the allocated
temporary buffer. This results in memory leak
Fix:
====
1) If not in flashback mode, destroy the memory for events once they are
processed.
2) Remove the ev->temp_buf=0 code for remote option. Let the proper cleanup to
be done as part of free_temp_buf().
Problem
-------
For one-statement contains multiple row events, Flashback didn't reverse the
sequence of row events inside one-statement.
Solution
--------
Using a new array 'events_in_stmt' to store the row events of one-statement,
when parsed the last one event, then print from the last one to the first one.
In the same time, fixed another bug, without -vv will not insert the table_map
into print_event_info->m_table_map, then change_to_flashback_event() will not
execute because of Table_map_log_event is empty.
When WSREP(thd) is not true we will use my_error(...) to print error. This
will set thd->is_error() to true and we wont be getting generic error.
Signed-off-by: Sachin Setiya <sachin.setiya@mariadb.com>
==== Description ====
Flashback can rollback the instances/databases/tables to an old snapshot.
It's implement on Server-Level by full image format binary logs (--binlog-row-image=FULL), so it supports all engines.
Currently, it’s a feature inside mysqlbinlog tool (with --flashback arguments).
Because the flashback binlog events will store in the memory, you should check if there is enough memory in your machine.
==== New Arguments to mysqlbinlog ====
--flashback (-B)
It will let mysqlbinlog to work on FLASHBACK mode.
==== New Arguments to mysqld ====
--flashback
Setup the server to use flashback. This enables binary log in row mode
and will enable extra logging for DDL's needed by flashback feature
==== Example ====
I have a table "t" in database "test", we can compare the output with "--flashback" and without.
#client/mysqlbinlog /data/mysqldata_10.0/binlog/mysql-bin.000001 -vv -d test -T t --start-datetime="2013-03-27 14:54:00" > /tmp/1.sql
#client/mysqlbinlog /data/mysqldata_10.0/binlog/mysql-bin.000001 -vv -d test -T t --start-datetime="2013-03-27 14:54:00" -B > /tmp/2.sql
Then, importing the output flashback file (/tmp/2.log), it can flashback your database/table to the special time (--start-datetime).
And if you know the exact postion, "--start-postion" is also works, mysqlbinlog will output the flashback logs that can flashback to "--start-postion" position.
==== Implement ====
1. As we know, if binlog_format is ROW (binlog-row-image=FULL in 10.1 and later), all columns value are store in the row event, so we can get the data before mis-operation.
2. Just do following things:
2.1 Change Event Type, INSERT->DELETE, DELETE->INSERT.
For example:
INSERT INTO t VALUES (...) ---> DELETE FROM t WHERE ...
DELETE FROM t ... ---> INSERT INTO t VALUES (...)
2.2 For Update_Event, swapping the SET part and WHERE part.
For example:
UPDATE t SET cols1 = vals1 WHERE cols2 = vals2
--->
UPDATE t SET cols2 = vals2 WHERE cols1 = vals1
2.3 For Multi-Rows Event, reverse the rows sequence, from the last row to the first row.
For example:
DELETE FROM t WHERE id=1; DELETE FROM t WHERE id=2; ...; DELETE FROM t WHERE id=n;
--->
DELETE FROM t WHERE id=n; ...; DELETE FROM t WHERE id=2; DELETE FROM t WHERE id=1;
2.4 Output those events from the last one to the first one which mis-operation happened.
For example:
