mysql慢sql實踐

今天學習了mysql的慢sql分析過程，作一下mark。

查詢慢sql的配置：

mysql> show variables like '%query%';
+------------------------------+-------------------------------+
| Variable_name                | Value                         |
+------------------------------+-------------------------------+
| binlog_rows_query_log_events | OFF                           |
| ft_query_expansion_limit     | 20                            |
| have_query_cache             | YES                           |
| long_query_time              | 10.000000                     |
| query_alloc_block_size       | 8192                          |
| query_cache_limit            | 33554432                      |
| query_cache_min_res_unit     | 4096                          |
| query_cache_size             | 268435456                     |
| query_cache_type             | OFF                           |
| query_cache_wlock_invalidate | OFF                           |
| query_prealloc_size          | 8192                          |
| slow_query_log               | ON                            |
| slow_query_log_file          | /var/log/mysql/query_slow.log |
+------------------------------+-------------------------------+

qcatch的參數：

mysql> SHOW VARIABLES LIKE '%query_cache%';
+------------------------------+-----------+
| Variable_name                | Value     |
+------------------------------+-----------+
| have_query_cache             | YES       |
| query_cache_limit            | 33554432  |
| query_cache_min_res_unit     | 4096      |
| query_cache_size             | 268435456 |
| query_cache_type             | OFF       |
| query_cache_wlock_invalidate | OFF       |
+------------------------------+-----------+
6 rows in set (0.00 sec)
mysql> SHOW VARIABLES LIKE '%qcache%';
Empty set (0.00 sec)
mysql> SHOW STATUS LIKE 'Qcache%';
+-------------------------+------------+
| Variable_name           | Value      |
+-------------------------+------------+
| Qcache_free_blocks      | 1          |
| Qcache_free_memory      | 268417440  |
| Qcache_hits             | 0          |
| Qcache_inserts          | 0          |
| Qcache_lowmem_prunes    | 0          |
| Qcache_not_cached       | 2211232422 |
| Qcache_queries_in_cache | 0          |
| Qcache_total_blocks     | 1          |
+-------------------------+------------+

查看一下，記錄執行的profiling是否是開啓動了，默認是不開啓的

mysql> show variables like "%pro%";

+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| have_profiling            | YES   |
| profiling                 | OFF   |
| profiling_history_size    | 15    |
| protocol_version          | 10    |
| proxy_user                |       |
| slave_compressed_protocol | OFF   |
| stored_program_cache      | 256   |
+---------------------------+-------+

開啓profile，操做：

set profiling = 1；

關閉profile，操做：set profiling = 0；

優化分析，profiles使用：

mysql> show profiles;
+----------+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Query_ID | Duration    | Query                                                                                                                                                                                                                                                                                                        |
+----------+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|        1 |  0.00076075 | show variables like "%pro%"                                                                                                                                                                                                                                                                                  |
|        2 | 18.95187850 | SELECT fr.id,fr.lendRequest_id,fr.operationType,fr.amount,fr.state,fr.transactionState,fr.payerAccountNumber,fr.payerBankName,fr.payerAccount,fr.repayDay,fr.logId,fr.createTime,log.finished,log.statusCode,lal.id as accountLogId,fr.inAdvanceRepayFlag FROM finance_requests fr LEFT JOIN unionpay_interf |
|        3 |  0.01064700 | select * from finance_requests limit 1

查看執行過程：show profile for query 2

+----------------------+-----------+
| Status               | Duration  |
+----------------------+-----------+
| starting             |  0.000161 |
| checking permissions |  0.000009 |
| checking permissions |  0.000004 |
| checking permissions |  0.000007 |
| Opening tables       |  0.000036 |
| init                 |  0.000073 |
| System lock          |  0.000015 |
| optimizing           |  0.000024 |
| statistics           |  0.000379 |
| preparing            |  0.000036 |
| Sorting result       |  0.000007 |
| executing            |  0.000005 |
| Sending data         |  0.000024 |
| Creating sort index  | 25.297675 |
| end                  |  0.000029 |
| query end            |  0.000009 |
| closing tables       |  0.000017 |
| freeing items        |  0.000058 |
| logging slow query   |  0.000099 |
| cleaning up          |  0.000094 |
+----------------------+-----------+
20 rows in set, 1 warning (0.00 sec)