①问题: 如何从一个大项目中,迅速的定位执行速度慢的语句(
show status;
+-----------------------------------------------+--------------+
| Variable_name | Value |
+-----------------------------------------------+--------------+
| Aborted_clients | 857 |
| Aborted_connects | 1820 |
| Binlog_cache_disk_use | 3 |
| Binlog_cache_use | 47355 |
| Binlog_stmt_cache_disk_use | 0 |
| Binlog_stmt_cache_use | 70 |
| Bytes_received | 376 |
| Bytes_sent | 2768 |
| Com_admin_commands | 0 |
| Com_assign_to_keycache | 0 |
| Com_alter_db | 0 |
| Com_alter_db_upgrade | 0 |
| Com_alter_event | 0 |
| Com_alter_function | 0 |
| Com_alter_procedure | 0 |
| Com_alter_server | 0 |
| Com_alter_table | 0 |
| Com_alter_tablespace | 0 |
| Com_alter_user | 0 |
| Com_analyze | 0 |
| Com_begin | 0 |
| Com_binlog | 0 |
| Com_call_procedure | 0 |
| Com_change_db | 1 |
| Com_change_master | 0 |
| Com_check | 0 |
| Com_checksum | 0 |
| Com_commit | 0 |
| Com_create_db | 0 |
| Com_create_event | 0 |
| Com_create_function | 0 |
| Com_create_index | 0 |
| Com_create_procedure | 0 |
| Com_create_server | 0 |
| Com_create_table | 0 |
| Com_create_trigger | 0 |
| Com_create_udf | 0 |
| Com_create_user | 0 |
| Com_create_view | 0 |
| Com_dealloc_sql | 0 |
| Com_delete | 0 |
| Com_delete_multi | 0 |
| Com_do | 0 |
| Com_drop_db | 0 |
| Com_drop_event | 0 |
| Com_drop_function | 0 |
| Com_drop_index | 0 |
| Com_drop_procedure | 0 |
| Com_drop_server | 0 |
| Com_drop_table | 0 |
| Com_drop_trigger | 0 |
| Com_drop_user | 0 |
| Com_drop_view | 0 |
| Com_empty_query | 0 |
| Com_execute_sql | 0 |
| Com_flush | 0 |
| Com_get_diagnostics | 0 |
| Com_grant | 0 |
| Com_ha_close | 0 |
| Com_ha_open | 0 |
| Com_ha_read | 0 |
| Com_help | 0 |
| Com_insert | 0 |
| Com_insert_select | 0 |
| Com_install_plugin | 0 |
| Com_kill | 0 |
| Com_load | 0 |
| Com_lock_tables | 0 |
| Com_optimize | 0 |
| Com_preload_keys | 0 |
| Com_prepare_sql | 0 |
| Com_purge | 0 |
| Com_purge_before_date | 0 |
| Com_release_savepoint | 0 |
| Com_rename_table | 0 |
| Com_rename_user | 0 |
| Com_repair | 0 |
| Com_replace | 0 |
| Com_replace_select | 0 |
| Com_reset | 0 |
| Com_resignal | 0 |
| Com_revoke | 0 |
| Com_revoke_all | 0 |
| Com_rollback | 0 |
| Com_rollback_to_savepoint | 0 |
| Com_savepoint | 0 |
| Com_select | 2 |
| Com_set_option | 1 |
| Com_signal | 0 |
| Com_show_binlog_events | 0 |
| Com_show_binlogs | 0 |
| Com_show_charsets | 0 |
| Com_show_collations | 0 |
| Com_show_create_db | 0 |
| Com_show_create_event | 0 |
| Com_show_create_func | 0 |
| Com_show_create_proc | 0 |
| Com_show_create_table | 0 |
| Com_show_create_trigger | 0 |
| Com_show_databases | 0 |
| Com_show_engine_logs | 0 |
| Com_show_engine_mutex | 0 |
| Com_show_engine_status | 0 |
| Com_show_events | 0 |
| Com_show_errors | 0 |
| Com_show_fields | 0 |
| Com_show_function_code | 0 |
| Com_show_function_status | 0 |
| Com_show_grants | 0 |
| Com_show_keys | 0 |
| Com_show_master_status | 0 |
| Com_show_open_tables | 0 |
| Com_show_plugins | 0 |
| Com_show_privileges | 0 |
| Com_show_procedure_code | 0 |
| Com_show_procedure_status | 0 |
| Com_show_processlist | 0 |
| Com_show_profile | 0 |
| Com_show_profiles | 0 |
| Com_show_relaylog_events | 0 |
| Com_show_slave_hosts | 0 |
| Com_show_slave_status | 0 |
| Com_show_status | 1 |
| Com_show_storage_engines | 0 |
| Com_show_table_status | 0 |
| Com_show_tables | 0 |
| Com_show_triggers | 0 |
| Com_show_variables | 0 |
| Com_show_warnings | 0 |
| Com_slave_start | 0 |
| Com_slave_stop | 0 |
| Com_stmt_close | 0 |
| Com_stmt_execute | 0 |
| Com_stmt_fetch | 0 |
| Com_stmt_prepare | 0 |
| Com_stmt_reprepare | 0 |
| Com_stmt_reset | 0 |
| Com_stmt_send_long_data | 0 |
| Com_truncate | 0 |
| Com_uninstall_plugin | 0 |
| Com_unlock_tables | 0 |
| Com_update | 0 |
| Com_update_multi | 0 |
| Com_xa_commit | 0 |
| Com_xa_end | 0 |
| Com_xa_prepare | 0 |
| Com_xa_recover | 0 |
| Com_xa_rollback | 0 |
| Com_xa_start | 0 |
| Compression | OFF |
| Connection_errors_accept | 0 |
| Connection_errors_internal | 0 |
| Connection_errors_max_connections | 0 |
| Connection_errors_peer_address | 5 |
| Connection_errors_select | 0 |
| Connection_errors_tcpwrap | 0 |
| Connections | 93538 |
| Created_tmp_disk_tables | 0 |
| Created_tmp_files | 231 |
| Created_tmp_tables | 0 |
| Delayed_errors | 0 |
| Delayed_insert_threads | 0 |
| Delayed_writes | 0 |
| Flush_commands | 1 |
| Handler_commit | 1 |
| Handler_delete | 0 |
| Handler_discover | 0 |
| Handler_external_lock | 2 |
| Handler_mrr_init | 0 |
| Handler_prepare | 0 |
| Handler_read_first | 1 |
| Handler_read_key | 1 |
| Handler_read_last | 0 |
| Handler_read_next | 0 |
| Handler_read_prev | 0 |
| Handler_read_rnd | 0 |
| Handler_read_rnd_next | 272432 |
| Handler_rollback | 0 |
| Handler_savepoint | 0 |
| Handler_savepoint_rollback | 0 |
| Handler_update | 0 |
| Handler_write | 0 |
| Innodb_buffer_pool_dump_status | not started |
| Innodb_buffer_pool_load_status | not started |
| Innodb_buffer_pool_pages_data | 6665 |
| Innodb_buffer_pool_bytes_data | 109199360 |
| Innodb_buffer_pool_pages_dirty | 0 |
| Innodb_buffer_pool_bytes_dirty | 0 |
| Innodb_buffer_pool_pages_flushed | 224366 |
| Innodb_buffer_pool_pages_free | 1024 |
| Innodb_buffer_pool_pages_misc | 502 |
| Innodb_buffer_pool_pages_total | 8191 |
| Innodb_buffer_pool_read_ahead_rnd | 0 |
| Innodb_buffer_pool_read_ahead | 60643 |
| Innodb_buffer_pool_read_ahead_evicted | 597 |
| Innodb_buffer_pool_read_requests | 464579038 |
| Innodb_buffer_pool_reads | 83120 |
| Innodb_buffer_pool_wait_free | 0 |
| Innodb_buffer_pool_write_requests | 3500136 |
| Innodb_data_fsyncs | 221493 |
| Innodb_data_pending_fsyncs | 0 |
| Innodb_data_pending_reads | 0 |
| Innodb_data_pending_writes | 0 |
| Innodb_data_read | 2366541824 |
| Innodb_data_reads | 85303 |
| Innodb_data_writes | 326326 |
| Innodb_data_written | 7686260736 |
| Innodb_dblwr_pages_written | 224366 |
| Innodb_dblwr_writes | 32146 |
| Innodb_have_atomic_builtins | ON |
| Innodb_log_waits | 0 |
| Innodb_log_write_requests | 579999 |
| Innodb_log_writes | 92128 |
| Innodb_os_log_fsyncs | 123073 |
| Innodb_os_log_pending_fsyncs | 0 |
| Innodb_os_log_pending_writes | 0 |
| Innodb_os_log_written | 318390272 |
| Innodb_page_size | 16384 |
| Innodb_pages_created | 13840 |
| Innodb_pages_read | 144308 |
| Innodb_pages_written | 224366 |
| Innodb_row_lock_current_waits | 0 |
| Innodb_row_lock_time | 58 |
| Innodb_row_lock_time_avg | 2 |
| Innodb_row_lock_time_max | 9 |
| Innodb_row_lock_waits | 25 |
| Innodb_rows_deleted | 108 |
| Innodb_rows_inserted | 768761 |
| Innodb_rows_read | 2513680333 |
| Innodb_rows_updated | 46782 |
| Innodb_num_open_files | 209 |
| Innodb_truncated_status_writes | 0 |
| Innodb_available_undo_logs | 128 |
| Key_blocks_not_flushed | 0 |
| Key_blocks_unused | 6668 |
| Key_blocks_used | 60 |
| Key_read_requests | 20089675 |
| Key_reads | 121 |
| Key_write_requests | 34 |
| Key_writes | 13 |
| Last_query_cost | 55011.199000 |
| Last_query_partial_plans | 1 |
| Max_used_connections | 41 |
| Not_flushed_delayed_rows | 0 |
| Open_files | 46 |
| Open_streams | 0 |
| Open_table_definitions | 314 |
| Open_tables | 126 |
| Opened_files | 34185 |
| Opened_table_definitions | 0 |
| Opened_tables | 0 |
| Performance_schema_accounts_lost | 0 |
| Performance_schema_cond_classes_lost | 0 |
| Performance_schema_cond_instances_lost | 0 |
| Performance_schema_digest_lost | 0 |
| Performance_schema_file_classes_lost | 0 |
| Performance_schema_file_handles_lost | 0 |
| Performance_schema_file_instances_lost | 0 |
| Performance_schema_hosts_lost | 0 |
| Performance_schema_locker_lost | 0 |
| Performance_schema_mutex_classes_lost | 0 |
| Performance_schema_mutex_instances_lost | 0 |
| Performance_schema_rwlock_classes_lost | 0 |
| Performance_schema_rwlock_instances_lost | 0 |
| Performance_schema_session_connect_attrs_lost | 0 |
| Performance_schema_socket_classes_lost | 0 |
| Performance_schema_socket_instances_lost | 0 |
| Performance_schema_stage_classes_lost | 0 |
| Performance_schema_statement_classes_lost | 0 |
| Performance_schema_table_handles_lost | 0 |
| Performance_schema_table_instances_lost | 136 |
| Performance_schema_thread_classes_lost | 0 |
| Performance_schema_thread_instances_lost | 0 |
| Performance_schema_users_lost | 0 |
| Prepared_stmt_count | 0 |
| Qcache_free_blocks | 1 |
| Qcache_free_memory | 1031360 |
| Qcache_hits | 0 |
| Qcache_inserts | 0 |
| Qcache_lowmem_prunes | 0 |
| Qcache_not_cached | 449697 |
| Qcache_queries_in_cache | 0 |
| Qcache_total_blocks | 1 |
| Queries | 4378247 |
| Questions | 7 |
| Select_full_join | 0 |
| Select_full_range_join | 0 |
| Select_range | 0 |
| Select_range_check | 0 |
| Select_scan | 1 |
| Slave_heartbeat_period | 0.000 |
| Slave_last_heartbeat | |
| Slave_open_temp_tables | 0 |
| Slave_received_heartbeats | 0 |
| Slave_retried_transactions | 0 |
| Slave_running | OFF |
| Slow_launch_threads | 0 |
| Slow_queries | 0 |
| Sort_merge_passes | 0 |
| Sort_range | 0 |
| Sort_rows | 0 |
| Sort_scan | 0 |
| Ssl_accept_renegotiates | 0 |
| Ssl_accepts | 0 |
| Ssl_callback_cache_hits | 0 |
| Ssl_cipher | |
| Ssl_cipher_list | |
| Ssl_client_connects | 0 |
| Ssl_connect_renegotiates | 0 |
| Ssl_ctx_verify_depth | 0 |
| Ssl_ctx_verify_mode | 0 |
| Ssl_default_timeout | 0 |
| Ssl_finished_accepts | 0 |
| Ssl_finished_connects | 0 |
| Ssl_server_not_after | |
| Ssl_server_not_before | |
| Ssl_session_cache_hits | 0 |
| Ssl_session_cache_misses | 0 |
| Ssl_session_cache_mode | NONE |
| Ssl_session_cache_overflows | 0 |
| Ssl_session_cache_size | 0 |
| Ssl_session_cache_timeouts | 0 |
| Ssl_sessions_reused | 0 |
| Ssl_used_session_cache_entries | 0 |
| Ssl_verify_depth | 0 |
| Ssl_verify_mode | 0 |
| Ssl_version | |
| Table_locks_immediate | 899684 |
| Table_locks_waited | 0 |
| Table_open_cache_hits | 1 |
| Table_open_cache_misses | 0 |
| Table_open_cache_overflows | 0 |
| Tc_log_max_pages_used | 0 |
| Tc_log_page_size | 0 |
| Tc_log_page_waits | 0 |
| Threads_cached | 6 |
| Threads_connected | 6 |
| Threads_created | 354 |
| Threads_running | 2 |
| Uptime | 4473505 |
| Uptime_since_flush_status | 4473505 |
+-----------------------------------------------+--------------+
341 rows in set
-
查询MySQL已经启动的时间
mysql> show status like 'uptime';
+---------------+---------+
| Variable_name | Value |
+---------------+---------+
| Uptime | 4473534 |
+---------------+---------+
1 row in set
-
查询执行了多少update/insert/select/delete操作
-- 如果你不写 [session|global] 默认是session 会话，指取出当前窗口的执行，如果你想看所有(从mysql 启动到现在，则应该 global)
mysql> show status like 'com_select';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Com_select | 2 |
+---------------+-------+
1 row in set
mysql> show global status like 'com_select';
+---------------+--------+
| Variable_name | Value |
+---------------+--------+
| Com_select | 495931 |
+---------------+--------+
1 row in set
-
查看MySQL有多少连接
mysql> show status like 'connections';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Connections | 93561 |
+---------------+-------+
1 row in set
-
显示慢查询次数
show global status like 'slow_queries';
②如何去定位慢查询
查看慢查询是否开启
mysql> show variables like '%slow_query_log%';
+---------------------+------------------------------+
| Variable_name | Value |
+---------------------+------------------------------+
| slow_query_log | OFF |
| slow_query_log_file | /var/lib/mysql/root-slow.log |
+---------------------+------------------------------+
2 rows in set (0.00 sec)
开启慢查询(只对当前数据库生效,重启则失效)
mysql> set global slow_query_log = 1;
Query OK, 0 rows affected
修改后需重新打开窗口
mysql> show variables like '%slow_query_log%';
+---------------------+------------------------------+
| Variable_name | Value |
+---------------------+------------------------------+
| slow_query_log | ON |
| slow_query_log_file | /var/lib/mysql/root-slow.log |
+---------------------+------------------------------+
2 rows in set (0.00 sec)
# 如要永久生效需修改my.cnf文件(不建议开启,影响性能)
slow_query_log = 1;
slow_query_log_file = /var/lib/mysql/root-slow.log
long_query_time=1
log_output = FILE
显示当前慢查询时间
show variables like 'long_query_time' ;
修改慢查询时间
set global long_query_time=1 ;
修改后需重新打开窗口
mysql> show variables like 'long_query_time';
+-----------------+----------+
| Variable_name | Value |
+-----------------+----------+
| long_query_time | 1.000000 |
+-----------------+----------+
1 row in set
③这时我们如果出现一条语句执行时间超过1秒中，就会统计到.
④测试,可以看到在日志中就记录下我们的mysql慢sql语句.
mysql> select sleep(2);
+----------+
| sleep(2) |
+----------+
| 0 |
+----------+
1 row in set (2.00 sec)
# 此时慢查询时间为1秒,上面SQL沉睡2秒,应当被记录
[root@root mysql]# pwd
/var/lib/mysql
[root@root mysql]# cat root-slow.log
/usr/sbin/mysqld, Version: 5.5.54-log (MySQL Community Server (GPL)). started with:
Tcp port: 3306 Unix socket: /var/lib/mysql/mysql.sock
Time Id Command Argument
/usr/sbin/mysqld, Version: 5.5.54-log (MySQL Community Server (GPL)). started with:
Tcp port: 3306 Unix socket: /var/lib/mysql/mysql.sock
Time Id Command Argument
# Time: 171229 0:20:39
# User@Host: root[root] @ localhost []
# Query_time: 2.000641 Lock_time: 0.000000 Rows_sent: 1 Rows_examined: 0
SET timestamp=1514478039;
select sleep(2);
⑤ 慢查询常用命令
# 得到记录集最多的10条SQL
mysqldumpslow -s r -t 10 /var/lib/mysql/root-slow.log
# 得到访问次数最多的10条SQL
mysqldumpslow -s c -t 10 /var/lib/mysql/root-slow.log
# 得到按时间排序的前10条含左连接的查询SQL
mysqldumpslow -s t -t 10 -g "left join" /var/lib/mysql/root-slow.log
# 为防止爆屏现象,命令应结合|和more使用
mysqldumpslow -s c -t 10 /var/lib/mysql/root-slow.log | more