In XtraDB we have the table INNODB_BUFFER_POOL_PAGES_INDEX which shows which pages belong to which indexes in which tables. Using thing information and standard TABLES table we can see how well different tables fit in buffer pool.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 | SELECT d.*, ROUND(100 * cnt * 16384 / ( data_length + index_length ), 2) fit FROM (SELECT schema_name, table_name, COUNT(*) cnt, SUM(dirty), SUM(hashed) FROM INNODB_BUFFER_POOL_PAGES_INDEX GROUP BY schema_name, table_name ORDER BY cnt DESC LIMIT 20) d JOIN TABLES ON ( TABLES.table_schema = d.schema_name AND TABLES.table_name = d.table_name ); +-------------+---------------------+---------+------------+-------------+--------+ | schema_name | table_name | cnt | sum(dirty) | sum(hashed) | fit | +-------------+---------------------+---------+------------+-------------+--------+ | db | table1 | 1699133 | 13296 | 385841 | 87.49 | | db | table2 | 1173272 | 17399 | 11099 | 98.42 | | db | table3 | 916641 | 7849 | 15316 | 94.77 | | db | table4 | 86999 | 1555 | 75554 | 87.42 | | db | table5 | 32701 | 7997 | 30082 | 91.61 | | db | table6 | 31990 | 4495 | 25681 | 102.97 | | db | table7 | 1 | 0 | 0 | 100.00 | +-------------+---------------------+---------+------------+-------------+--------+ 7 rows in set (26.45 sec) |
You can also see in one of the cases the value shown is a bit over 100% – I am not sure where it comes from but more pages reported to belong to the table in buffer pool than on disk. Though it seems to work well enough for estimation purposes.
UPDATE: We have changed the Schema in newer Percona Server versions and this exact query will no more work. The correct query is described in this post
That is awesome. Wish I had this sort of feature back in the day.
a generic version work with partitions
SELECT d.*,round(100*cnt*16384/(data_length+index_length),2) fit
FROM (SELECT schema_name,
replace(substring_index(table_name, ‘#’, 3), ‘#mysql50#’, ”) as xtable_name,
substring_index(table_name, ‘#’, -1) as partition_name,
count(*) cnt,sum(dirty),sum(hashed)
FROM INNODB_BUFFER_POOL_PAGES_INDEX GROUP BY schema_name,table_name
ORDER BY cnt DESC LIMIT 20) d JOIN TABLES
ON (TABLES.table_schema=d.schema_name AND TABLES.table_name=d.xtable_name);
Bash99,
Thanks. Great.
Peter, this query does not work on 5.5
INNODB_BUFFER_POOL_PAGES_INDEX no longer contains schema_name column, so query fails on this.
Do you have an updated version of the same query, but for rel 5.5?
Cheers
//Steve