MySQL 中information_schema、mysql、performance_schema、sys 簡介
一、information_schema簡介
在MySQL中，把 information_schema 看作是一個數據庫，確切說是資訊資料庫。其中儲存著關於MySQL伺服器所維護的所有其他資料庫的資訊。如資料庫名，資料庫的表，表欄的資料型別與訪問權 限等。在INFORMATION_SCHEMA中，有數個只讀表。它們實際上是檢視，而不是基本表，因此，你將無法看到與之相關的任何檔案。
information_schema資料庫表說明:
1 1、SCHEMATA表：提供了當前mysql例項中所有資料庫的資訊。是show databases的結果取之此表。 2 3 2、TABLES表：提供了關於資料庫中的表的資訊（包括檢視）。詳細表述了某個表屬於哪個schema，表型別，表引擎，建立時間等資訊。是show tables from schemaname的結果取之此表。4 5 3、COLUMNS表：提供了表中的列資訊。詳細表述了某張表的所有列以及每個列的資訊。是show columns from schemaname.tablename的結果取之此表。 6 7 4、STATISTICS表：提供了關於表索引的資訊。是show index from schemaname.tablename的結果取之此表。 8 9 5、USER_PRIVILEGES（使用者許可權）表：給出了關於全程許可權的資訊。該資訊源自mysql.user授權表。是非標準表。 10 11 6、SCHEMA_PRIVILEGES（方案許可權）表：給出了關於方案（資料庫）許可權的資訊。該資訊來自mysql.db授權表。是非標準表。12 13 7、TABLE_PRIVILEGES（表許可權）表：給出了關於表許可權的資訊。該資訊源自mysql.tables_priv授權表。是非標準表。 14 15 8、COLUMN_PRIVILEGES（列許可權）表：給出了關於列許可權的資訊。該資訊源自mysql.columns_priv授權表。是非標準表。 16 17 9、CHARACTER_SETS（字符集）表：提供了mysql例項可用字符集的資訊。是SHOW CHARACTER SET結果集取之此表。 18 19 10、COLLATIONS表：提供了關於各字符集的對照資訊。 20 21 11、COLLATION_CHARACTER_SET_APPLICABILITY表：指明瞭可用於校對的字符集。這些列等效於SHOW COLLATION的前兩個顯示欄位。22 23 12、TABLE_CONSTRAINTS表：描述了存在約束的表。以及表的約束型別。 24 25 13、KEY_COLUMN_USAGE表：描述了具有約束的鍵列。 26 27 14、ROUTINES表：提供了關於儲存子程式（儲存程式和函式）的資訊。此時，ROUTINES表不包含自定義函式（UDF）。名為“mysql.proc name”的列指明瞭對應於INFORMATION_SCHEMA.ROUTINES表的mysql.proc表列。 28 29 15、VIEWS表：給出了關於資料庫中的檢視的資訊。需要有show views許可權，否則無法檢視檢視資訊。 30 31 16、TRIGGERS表：提供了關於觸發程式的資訊。必須有super許可權才能檢視該表
檢視引擎
information_schema.ENGINS 對應於 show engines;
檢視資料庫
information_schema.SCHEMATA 對應於 show databases;
查看錶
information_schema.TABLES 對應於 show tables;
檢視列
information_schema.COLUMNS 對應於show columns from table_name
檢視索引
information_schema.STATISTICS 對應於show index from table_name
檢視執行緒
information_schema.PROCESSLIST 對應於 show processlist
二.MySQL 庫表簡介
在mysql資料庫中，有mysql_install_db指令碼初始化許可權表，儲存許可權的表有： 1、user表: 使用者列、許可權列、安全列、資源控制列 2、db表 : 使用者列、許可權列 3、host表 4、table_priv表 5、columns_priv表 6、proc_priv表
三.sys庫表簡介
sys_config ： 這是在這個系統庫上存在的唯一一個表了, 表結構如下： CREATE TABLE `sys_config` ( `variable` varchar(128) NOT NULL, `value` varchar(128) DEFAULT NULL, `set_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, `set_by` varchar(128) DEFAULT NULL, PRIMARY KEY (`variable`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 • variable ： 配置選項名稱 • value ： 配置選項值 • set_time： 該行配置修改的時間 • set_by ： 該行配置資訊修改者，如果從被安裝沒有修改過，那麼這個資料應該為NULL 這裡寫圖片描述 以上值的會話變數為@sys.+表中variable欄位，譬如：@sys.statement_truncate_len 可以set @sys.statement_truncate_len = 32 臨時改變值，在會話中會一直使用這個值，如果想要恢復使用表的預設值，只需要將這個會話值設定為null；set @sys.statement_truncate_len = null; • diagnostics.allow_i_s_tables : 預設為OFF ，如果開啟表示允許diagnostics() 儲存過程執行掃描information_schema.tables 表，如果表很多，那麼可能會很耗效能， • diagnostics.include_raw : 預設為OFF ， 開啟將會從metrics 檢視輸出未加工處理的資料 。 • statement_performance_analyzer.limit : 檢視在沒有加limit限制時，返回的最大行數 • statement_performance_analyzer.view • statement_truncate_len : 通過format_statement()函式返回值的最大長度 這個表非預設選項還有一個@sys.debug引數 , 可以手動加入: INSERT INTO sys_config (variable, value) VALUES('debug', 'ON'); UPDATE sys_config SET value = 'OFF' WHERE variable = 'debug'; SET @sys.debug = NULL;
四.performance_schema庫表簡介
1 performance_schema是執行在較低級別的用於監控MySQL Server執行過程中的資源消耗、資源等待等情況的一個功能特性，也是一個儲存引擎。該特性具有以下特點。 2 3 提供了一種在資料庫執行時實時檢查Server內部執行情況的方法 4 可監控任何事情以及對應的時間消耗，利用這些資訊來判斷Server中的相關資源消耗 5 只被記錄在本地Server的performance_schema中，其表中資料發生變化時不會被寫入binlog中，也不會通過複製機制被複制到其他Server中 6 對於這些表可使用SELECT語句查詢，也可以使用SQL語句更新performance_schema資料庫中的表記錄，但不建議更新，會影響後續的資料收集 7 表中資料不會持久化儲存在磁碟中，而是儲存在記憶體中，一旦伺服器重啟，這些資料就會丟失 8 不會導致server的行為發生變化（查詢，優化等） 9 總體上開銷有限也不會影響效能 10 對某事件監測失敗，不影響server正常執行 11 當針對一個數據，同時被performance_schema收集和查詢，則收集優先與查詢 12 事件監測點可進行配置
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檢視是否當前資料庫是否支援
mysql> sho engines; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'sho engines' at line 1 mysql> show engines; +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | Engine | Support | Comment | Transactions | XA | Savepoints | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL | | MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO | | InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES | | PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO | | MyISAM | YES | MyISAM storage engine | NO | NO | NO | | MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO | | BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO | | CSV | YES | CSV storage engine | NO | NO | NO | | ARCHIVE | YES | Archive storage engine | NO | NO | NO | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ 9 rows in set (0.00 sec)
Support 為YES 表示支援 - 檢視該特性是否使能
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1 mysql> show variables like 'performance_schema'; 2 +--------------------+-------+ 3 | Variable_name | Value | 4 +--------------------+-------+ 5 | performance_schema | ON | 6 +--------------------+-------+ 7 1 row in set (0.00 sec)
如果為off則表示未使能。該引數為只讀引數，則可在mysql.cnf中進行配置後重啟服務使用該引擎的這些表的分類
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1）語句事件記錄表 mysql> show tables like 'events_statement%'; +----------------------------------------------------+ | Tables_in_performance_schema (events_statement%) | +----------------------------------------------------+ | events_statements_current | //當前語句事件表 | events_statements_histogram_by_digest | //歷史語句事件表 | events_statements_histogram_global | | events_statements_history | | events_statements_history_long | //長語句歷史事件表 | events_statements_summary_by_account_by_event_name | //聚合後的摘要表 | events_statements_summary_by_digest | | events_statements_summary_by_host_by_event_name | | events_statements_summary_by_program | | events_statements_summary_by_thread_by_event_name | | events_statements_summary_by_user_by_event_name | | events_statements_summary_global_by_event_name | +----------------------------------------------------+ 12 rows in set (0.00 sec) 2）等待時間記錄表 mysql> show tables like 'events_wait%'; +-----------------------------------------------+ | Tables_in_performance_schema (events_wait%) | +-----------------------------------------------+ | events_waits_current | | events_waits_history | | events_waits_history_long | | events_waits_summary_by_account_by_event_name | | events_waits_summary_by_host_by_event_name | | events_waits_summary_by_instance | | events_waits_summary_by_thread_by_event_name | | events_waits_summary_by_user_by_event_name | | events_waits_summary_global_by_event_name | +-----------------------------------------------+ 9 rows in set (0.00 sec) 3）階段事件記錄表 mysql> show tables like 'events_stage%'; +------------------------------------------------+ | Tables_in_performance_schema (events_stage%) | +------------------------------------------------+ | events_stages_current | | events_stages_history | | events_stages_history_long | | events_stages_summary_by_account_by_event_name | | events_stages_summary_by_host_by_event_name | | events_stages_summary_by_thread_by_event_name | | events_stages_summary_by_user_by_event_name | | events_stages_summary_global_by_event_name | +------------------------------------------------+ 8 rows in set (0.00 sec) 4）事務事件記錄表 mysql> show tables like 'events_transaction%'; +------------------------------------------------------+ | Tables_in_performance_schema (events_transaction%) | +------------------------------------------------------+ | events_transactions_current | | events_transactions_history | | events_transactions_history_long | | events_transactions_summary_by_account_by_event_name | | events_transactions_summary_by_host_by_event_name | | events_transactions_summary_by_thread_by_event_name | | events_transactions_summary_by_user_by_event_name | | events_transactions_summary_global_by_event_name | +------------------------------------------------------+ 8 rows in set (0.00 sec) 5）監控檔案系統層呼叫的表 mysql> show tables like '%file%'; +---------------------------------------+ | Tables_in_performance_schema (%file%) | +---------------------------------------+ | file_instances | | file_summary_by_event_name | | file_summary_by_instance | +---------------------------------------+ 3 rows in set (0.00 sec) 6）監視記憶體使用的表 mysql> show tables like '%memory%'; +-----------------------------------------+ | Tables_in_performance_schema (%memory%) | +-----------------------------------------+ | memory_summary_by_account_by_event_name | | memory_summary_by_host_by_event_name | | memory_summary_by_thread_by_event_name | | memory_summary_by_user_by_event_name | | memory_summary_global_by_event_name | +-----------------------------------------+ 5 rows in set (0.00 sec) 7）動態對performance_schema進行配置的配置表 mysql> show tables like '%setup%'; +----------------------------------------+ | Tables_in_performance_schema (%setup%) | +----------------------------------------+ | setup_actors | | setup_consumers | | setup_instruments | | setup_objects | | setup_threads | +----------------------------------------+ 5 rows in set (0.01 sec)
查詢效能表進行進行分析
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兩個基本概念 ● instruments：生產者，用於採集MySQL中各種操作產生的事件資訊，對應配置表中的配置項，我們可以稱之為事件採集配置項。以下提及的生產者均統稱為instruments。 ● consumers：消費者，對應的消費者表用於儲存來自instruments採集的資料，對應配置表中的配置項，我們可以稱之為消費儲存配置項。以下提及的消費者均統稱為consumers。 1、哪類的SQL執行最多？ mysql> SELECT DIGEST_TEXT,COUNT_STAR,FIRST_SEEN,LAST_SEEN FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC -> ; +----------------------------------------------------------------------------------------------------------------------------------------+------------+----------------------------+----------------------------+ | DIGEST_TEXT | COUNT_STAR | FIRST_SEEN | LAST_SEEN | +----------------------------------------------------------------------------------------------------------------------------------------+------------+----------------------------+----------------------------+ | SHOW VARIABLES LIKE ? | 4 | 2022-01-04 18:14:24.153156 | 2022-01-04 21:25:12.396097 | | SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 3 | 2022-01-04 18:06:55.067124 | 2022-01-04 18:21:09.809550 | 2、哪類SQL的平均響應時間最多？ mysql> SELECT DIGEST_TEXT,AVG_TIMER_WAIT FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC ; +----------------------------------------------------------------------------------------------------------------------------------------+----------------+ | DIGEST_TEXT | AVG_TIMER_WAIT | +----------------------------------------------------------------------------------------------------------------------------------------+----------------+ | SHOW VARIABLES LIKE ? | 5867400000 | | SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 42246300000 | 3、哪類SQL排序記錄數最多？ mysql> SELECT DIGEST_TEXT,SUM_SORT_ROWS FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC; +----------------------------------------------------------------------------------------------------------------------------------------+---------------+ | DIGEST_TEXT | SUM_SORT_ROWS | +----------------------------------------------------------------------------------------------------------------------------------------+---------------+ | SHOW VARIABLES LIKE ? | 0 | 4、哪類SQL掃描記錄數最多？ mysql> SELECT DIGEST_TEXT,SUM_ROWS_EXAMINED FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC; +----------------------------------------------------------------------------------------------------------------------------------------+-------------------+ | DIGEST_TEXT | SUM_ROWS_EXAMINED | +----------------------------------------------------------------------------------------------------------------------------------------+-------------------+ | SHOW VARIABLES LIKE ? | 51 | 5、哪類SQL使用臨時表最多？ mysql> SELECT DIGEST_TEXT,SUM_CREATED_TMP_TABLES,SUM_CREATED_TMP_DISK_TABLES FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC; +----------------------------------------------------------------------------------------------------------------------------------------+------------------------+-----------------------------+ | DIGEST_TEXT | SUM_CREATED_TMP_TABLES | SUM_CREATED_TMP_DISK_TABLES | +----------------------------------------------------------------------------------------------------------------------------------------+------------------------+-----------------------------+ | SHOW VARIABLES LIKE ? | 4 | 0 | | SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 0 | 0 | 6、哪類SQL返回結果集最多？ mysql> SELECT DIGEST_TEXT,SUM_ROWS_SENT FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC; +-------------------------------------------------------------------------------------------------------------------------------------------------------+---------------+ | DIGEST_TEXT | SUM_ROWS_SENT | +-------------------------------------------------------------------------------------------------------------------------------------------------------+---------------+ | SHOW VARIABLES LIKE ? | 51 | | SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 38 | 7、哪個表物理IO最多？ mysql> SELECT file_name,event_name,SUM_NUMBER_OF_BYTES_READ,SUM_NUMBER_OF_BYTES_WRITE FROM file_summary_by_instance ORDER BY SUM_NUMBER_OF_BYTES_READ + SUM_NUMBER_OF_BYTES_WRITE DESC; +------------------------------------------+---------------------------------------+--------------------------+---------------------------+ | file_name | event_name | SUM_NUMBER_OF_BYTES_READ | SUM_NUMBER_OF_BYTES_WRITE | +------------------------------------------+---------------------------------------+--------------------------+---------------------------+ | /var/lib/mysql/ibtmp1 | wait/io/file/innodb/innodb_data_file | 0 | 14729216 | | /var/lib/mysql/#ib_16384_1.dblwr | wait/io/file/innodb/innodb_dblwr_file | 8585216 | 0 | 8、哪個表邏輯IO最多？ mysql> SELECT object_name,COUNT_READ,COUNT_WRITE,COUNT_FETCH,SUM_TIMER_WAIT FROM table_io_waits_summary_by_table ORDER BY sum_timer_wait DESC; +------------------------------------------------------+------------+-------------+-------------+----------------+ | object_name | COUNT_READ | COUNT_WRITE | COUNT_FETCH | SUM_TIMER_WAIT | +------------------------------------------------------+------------+-------------+-------------+----------------+ | books | 1 | 1 | 1 | 14683357736 | | dd_properties | 0 | 0 | 0 | 0 |
9、哪個索引訪問最多？mysql> SELECT OBJECT_NAME,INDEX_NAME,COUNT_FETCH,COUNT_INSERT,COUNT_UPDATE,COUNT_DELETE FROM table_io_waits_summary_by_index_usage ORDER BY SUM_TIMER_WAIT DESC;
+------------------------------------------------------+----------------------------------+-------------+--------------+--------------+--------------+
| OBJECT_NAME | INDEX_NAME | COUNT_FETCH | COUNT_INSERT | COUNT_UPDATE | COUNT_DELETE |
+------------------------------------------------------+----------------------------------+-------------+--------------+--------------+--------------+
| books | NULL | 1 | 1 | 0 | 0 |10、哪個索引從來沒有用過？
mysql> SELECT OBJECT_SCHEMA,OBJECT_NAME,INDEX_NAME FROM table_io_waits_summary_by_index_usage WHERE INDEX_NAME IS NOT NULL AND COUNT_STAR = 0 AND OBJECT_SCHEMA <> 'mysql' ORDER BY OBJECT_SCHEMA,OBJECT_NAME;
+--------------------+------------------------------------------------------+----------------------------------+
| OBJECT_SCHEMA | OBJECT_NAME | INDEX_NAME |
+--------------------+------------------------------------------------------+----------------------------------+
| cara_testing_db | books | PRIMARY |
| performance_schema | accounts | ACCOUNT |11、哪個等待事件消耗時間最多？
mysql> SELECT EVENT_NAME,COUNT_STAR,SUM_TIMER_WAIT,AVG_TIMER_WAIT FROM events_waits_summary_global_by_event_name WHERE event_name != 'idle' ORDER BY SUM_TIMER_WAIT DESC ;
+---------------------------------------------------------------------+------------+----------------+----------------+
| EVENT_NAME | COUNT_STAR | SUM_TIMER_WAIT | AVG_TIMER_WAIT |
+---------------------------------------------------------------------+------------+----------------+----------------+
| wait/io/file/innodb/innodb_data_file | 1103 | 686179063712 | 622102240 |
| wait/io/file/innodb/innodb_dblwr_file | 30 | 118918612832 | 3963953732 |
| wait/io/file/innodb/innodb_log_file | 109 | 66884431760 | 613618552 |12、剖析某條SQL的執行情況，包括statement資訊，stege資訊，wait資訊
mysql> SELECT EVENT_ID,sql_text FROM events_statements_history WHERE sql_text LIKE '%count(*)%';
+----------+----------------------------+
| EVENT_ID | sql_text |
+----------+----------------------------+
| 155 | select count(*) from books |
+----------+----------------------------+
1 row in set (0.00 sec)13、檢視每個階段的時間消耗
mysql> SELECT event_id,EVENT_NAME,SOURCE,TIMER_END - TIMER_START FROM events_stages_history_long WHERE NESTING_EVENT_ID = 1553
-> ;
Empty set (0.01 sec)14、檢視每個階段的鎖等待情況
mysql> SELECT event_id,event_name,source,timer_wait,object_name,index_name,operation,nesting_event_id FROM events_waits_history_long;