| Bug #18269 | update query's problem (about atomical property) | ||
|---|---|---|---|
| Submitted: | 16 Mar 2006 7:01 | Modified: | 26 Apr 2006 4:33 |
| Reporter: | park ji hyeon | Email Updates: | |
| Status: | Not a Bug | Impact on me: | |
| Category: | MySQL Server | Severity: | S3 (Non-critical) |
| Version: | 4.1.12-log | OS: | Linux (Red Hat Enterprise Linux ES) |
| Assigned to: | CPU Architecture: | Any | |
[16 Mar 2006 7:01]
park ji hyeon
[16 Mar 2006 8:35]
Valeriy Kravchuk
Thank you for a problem report. Please, send the results of SHOW VARIABLES command from your server. I wonder what is the value of innodb_locks_unsafe_for_binlog, for example. A more precise description of a test case, including CREATE TABLE and, maybe, binlog, will be also useful.
[17 Mar 2006 0:18]
park ji hyeon
+ Show variables Results
-------------------------------------------
Variable_name Value
back_log 50
basedir /usr/
bdb_cache_size 8388600
bdb_home /var/lib/mysql/
bdb_log_buffer_size 262144
bdb_logdir
bdb_max_lock 10000
bdb_shared_data OFF
bdb_tmpdir /tmp/
binlog_cache_size 32768
bulk_insert_buffer_size 8388608
character_set_client euckr
character_set_connection euckr
character_set_database euckr
character_set_results euckr
character_set_server euckr
character_set_system utf8
character_sets_dir /usr/share/mysql/charsets/
collation_connection euckr_korean_ci
collation_database euckr_korean_ci
collation_server euckr_korean_ci
concurrent_insert ON
connect_timeout 5
datadir /var/lib/mysql/
date_format %Y-%m-%d
datetime_format %Y-%m-%d %H:%i:%s
default_week_format 0
delay_key_write ON
delayed_insert_limit 100
delayed_insert_timeout 300
delayed_queue_size 1000000
expire_logs_days 0
flush OFF
flush_time 0
ft_boolean_syntax + -><()~*:""&|
ft_max_word_len 84
ft_min_word_len 4
ft_query_expansion_limit 20
ft_stopword_file (built-in)
group_concat_max_len 1024
have_archive NO
have_bdb YES
have_blackhole_engine NO
have_compress YES
have_crypt YES
have_csv NO
have_example_engine NO
have_geometry YES
have_innodb YES
have_isam YES
have_ndbcluster NO
have_openssl YES
have_query_cache YES
have_raid NO
have_rtree_keys YES
have_symlink YES
init_connect set names euckr
init_file
init_slave
innodb_additional_mem_pool_size 1048576
innodb_autoextend_increment 8
innodb_buffer_pool_awe_mem_mb 0
innodb_buffer_pool_size 8388608
innodb_data_file_path ibdata1:10M:autoextend
innodb_data_home_dir
innodb_fast_shutdown ON
innodb_file_io_threads 4
innodb_file_per_table OFF
innodb_flush_log_at_trx_commit 1
innodb_flush_method
innodb_force_recovery 0
innodb_lock_wait_timeout 50
innodb_locks_unsafe_for_binlog OFF
innodb_log_arch_dir
innodb_log_archive OFF
innodb_log_buffer_size 1048576
innodb_log_file_size 5242880
innodb_log_files_in_group 2
innodb_log_group_home_dir ./
innodb_max_dirty_pages_pct 90
innodb_max_purge_lag 0
innodb_mirrored_log_groups 1
innodb_open_files 300
innodb_table_locks ON
innodb_thread_concurrency 8
interactive_timeout 28800
join_buffer_size 131072
key_buffer_size 402653184
key_cache_age_threshold 300
key_cache_block_size 1024
key_cache_division_limit 100
language /usr/share/mysql/english/
large_files_support ON
license GPL
local_infile ON
locked_in_memory OFF
log OFF
log_bin ON
log_error
log_slave_updates OFF
log_slow_queries ON
log_update OFF
log_warnings 1
long_query_time 10
low_priority_updates OFF
lower_case_file_system OFF
lower_case_table_names 0
max_allowed_packet 1047552
max_binlog_cache_size 18446744073709551615
max_binlog_size 1073741824
max_connect_errors 1000
max_connections 500
max_delayed_threads 20
max_error_count 64
max_heap_table_size 104856576
max_insert_delayed_threads 20
max_join_size 18446744073709551615
max_length_for_sort_data 1024
max_relay_log_size 0
max_seeks_for_key 18446744073709551615
max_sort_length 1024
max_tmp_tables 32
max_user_connections 0
max_write_lock_count 18446744073709551615
myisam_data_pointer_size 4
myisam_max_extra_sort_file_size 2147483648
myisam_max_sort_file_size 9223372036854775807
myisam_recover_options OFF
myisam_repair_threads 1
myisam_sort_buffer_size 67108864
net_buffer_length 16384
net_read_timeout 30
net_retry_count 10
net_write_timeout 60
new OFF
old_passwords OFF
open_files_limit 2510
pid_file /var/run/mysqld/mysqld.pid
port 3306
preload_buffer_size 32768
protocol_version 10
query_alloc_block_size 8192
query_cache_limit 1048576
query_cache_min_res_unit 4096
query_cache_size 67108864
query_cache_type ON
query_cache_wlock_invalidate OFF
query_prealloc_size 8192
range_alloc_block_size 2048
read_buffer_size 2093056
read_only OFF
read_rnd_buffer_size 262144
relay_log_purge ON
relay_log_space_limit 0
rpl_recovery_rank 0
secure_auth OFF
server_id 1
skip_external_locking ON
skip_networking OFF
skip_show_database OFF
slave_net_timeout 3600
slave_transaction_retries 0
slow_launch_time 2
socket /var/lib/mysql/mysql.sock
sort_buffer_size 2097144
sql_mode
storage_engine MyISAM
sql_notes ON
sql_warnings ON
sync_binlog 0
sync_replication 0
sync_replication_slave_id 0
sync_replication_timeout 0
sync_frm ON
system_time_zone KST
table_cache 512
table_type MyISAM
thread_cache_size 8
thread_stack 196608
time_format %H:%i:%s
time_zone SYSTEM
tmp_table_size 33554432
tmpdir
transaction_alloc_block_size 8192
transaction_prealloc_size 4096
tx_isolation REPEATABLE-READ
version 4.1.12-log
version_bdb Sleepycat Software: Berkeley DB 4.1.24: (May 13, 2005)
version_comment Source distribution
version_compile_machine x86_64
version_compile_os redhat-linux-gnu
wait_timeout 28800
------------------------------------------------------
table name : let "table" at my option.
+ Source code
//when user buys item.
$balance = mysql_fetch_object(mysql_query("SELECT money, point, mileage FROM table WHERE user_id = '$user_id'",$db_conn)); //check the balance in an account
$amount = $balance->money + $balance->point + $balance->mileage; //sum
include "change.inc"; //compute money, point, mileage -> afterMoney, afterPoint, afterMileage
if($balance >= $priceOfItem) {
$deductMoney = mysql_query("UPDATE table SET money = afterMoney , point = afterPoint , mileage = afterMileage WHERE user_id = 'user_id' and money = $balance->money and point = $balance->point and mileage = $balance->mileage",$db_conn);
}
+binlog
# at 42671218
#060316 2:40:31 server id 1 log_pos 42671218 Query thread_id=220925419 exec_time=0 error_code=0
SET TIMESTAMP=1142444431;
UPDATE table SET money = 13000, point = 0, mileage = 0 WHERE user_id = 'test_id' and money = 24000 and point = 0 and mileage = 0
nd money4 = '0';
# at 42671404
#060316 2:40:31 server id 1 log_pos 42671404 Query thread_id=220925420 exec_time=0 error_code=0
SET TIMESTAMP=1142444431;
UPDATE table SET money = 15000, point = 0, mileage = 0 WHERE user_id = 'test_id' and money = 24000 and point = 0 and mileage = 0
nd money4 = '0';
+ schema
CREATE TABLE `table` (
`id` int(11) NOT NULL default '0',
`user_id` varchar(30) default NULL,
`money` int(11) unsigned NOT NULL default '0',
`point` int(11) unsigned NOT NULL default '0',
`mileage` int(11) unsigned NOT NULL default '0',
`tran_counter` mediumint(8) unsigned default '0',
UNIQUE KEY `id` (`id`),
KEY `user_id` (`user_id`)
) ENGINE=MyISAM DEFAULT CHARSET=euckr
+ description
As you show, I don't use Innodb and transaction.
I want to comment about Update query's execution only.
at binlog :
UPDATE table SET money = 13000, point = 0, mileage = 0 WHERE user_id = 'test_id' and money = 24000 and point = 0 and mileage = 0
nd money4 = '0';
UPDATE table SET money = 15000, point = 0, mileage = 0 WHERE user_id = 'test_id' and money = 24000 and point = 0 and mileage = 0
nd money4 = '0';
Is it possible?
binlog records queries that associated writing & succeeded(finished) work.
According to result, I think that update execute in non-isolation.
when same query's execution happen concurrently,
If second query's "where" next phrase (read working) execute before first query's writing completed....It's possible.
So I test that 'table lock' allocate update query's before and after.
but result is same.
Should I use transaction(on Innodb engine)?
Please let me know, your opinion & result that try to find the cause of it.
[24 Apr 2006 15:23]
Valeriy Kravchuk
You need to use InnoDB tables to get ACID properties of transactions, in general. As for your updates of MyISAM table, they are atomic, but not concurrent anyway - they are serialized (by means of table-level locks) and executed one after the other, just as shown in the binary log. I see no bugs in this report.
[26 Apr 2006 4:33]
park ji hyeon
Thank you for your comment. As you said, If they are serialized I think that it would not be happened. Even though MyIsam doesn't server concurrency control if it has serializability, there's no problem. It just makes decreasing of speed. Problem is isolation level. It seems like "uncommitted read"
[28 May 2006 9:04]
Sergei Golubchik
You seem to believe that if update did not match/modify any rows it should not be written to binlog. This is wrong, a query is written to binlog even if it has not done anything. Try, for example, to create an empty table, and run an update on it - it will be written to binlog.
