MySQL: Useful queries

mysql.sql

-- List running queries

SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST WHERE command = "Query" ORDER BY TIME DESC;

-- Indexes size
SELECT database_name, table_name, index_name, stat_value AS pages,
round(stat_value*@@innodb_page_size/1024/1024, 2) size_in_mb
FROM mysql.innodb_index_stats
WHERE stat_name = 'size'
ORDER BY 4 DESC;

-- Number of cached pages in innodb buffer pool
select count(*) from information_schema.innodb_buffer_page;

-- How much of each index is currently cached in innodb buffer pool
select
table_name as Table_Name, index_name as Index_Name,
count(*) as Page_Count, sum(data_size)/1024/1024 as Size_in_MB
from information_schema.innodb_buffer_page
group by table_name, index_name
order by Size_in_MB desc;

-- Page types cached in innodb pool
select
page_type as Page_Type,
sum(data_size)/1024/1024 as Size_in_MB
from information_schema.innodb_buffer_page
group by page_type
order by Size_in_MB desc;

-- See table estimated size (based on statistics)
SELECT
  ENGINE AS 'Engine',
  ROW_FORMAT AS 'Row Format',
  TABLE_ROWS AS 'Est. # rows',
  AUTO_INCREMENT AS 'Max. auto-inc ID',
  AVG_ROW_LENGTH AS 'Est. avg row size (bytes)',
  DATA_LENGTH / 1024 / 1024 AS 'Est. data size (MB)',
  INDEX_LENGTH / 1024 / 1024 AS 'Est. index size (MB)',
  (DATA_LENGTH + INDEX_LENGTH) / 1024 / 1024 AS 'Est. total size (MB)'
FROM
  information_schema.TABLES
WHERE
  TABLE_NAME = "table_name";

-- List MySQL variables
SHOW VARIABLES;