inserts and updates to MRG_MYISAM table not tracked in TABLE_STATISTICS

[Dan Edwards]

I just upgraded from mysql 5.0 to percona 5.1.55. I noticed that TABLE_STATISTICS.ROWS_CHANGED was 0 for some of our busiest tables. I narrowed it down too those tables were using the MRG_MYISAM engine. It did not record ROWS_CHANGED for either the merge table or the underlying MYISAM tables.

Here is sql to reproduce:

CREATE TABLE mrg_tbl1 (id INT(11) NOT NULL AUTO_INCREMENT, field1 INT(11) NULL DEFAULT NULL, PRIMARY KEY (id)) ENGINE=MYISAM;

CREATE TABLE mrg_tbl2 (id INT(11) NOT NULL AUTO_INCREMENT, field1 INT(11) NULL DEFAULT NULL, PRIMARY KEY (id)) ENGINE=MYISAM;

CREATE TABLE mrg_tbl ( id INT(11) NOT NULL AUTO_INCREMENT, field1 INT(11) NULL DEFAULT NULL, PRIMARY KEY (id)) ENGINE=MRG_MYISAM UNION=(mrg_tbl1, mrg_tbl2) INSERT_METHOD=LAST;

insert into mrg_tbl (field1) Values(10),(11),(12) ;
update mrg_tbl set field1=20 where field1=10;

select * from mrg_tbl;

select * from information_schema.TABLE_STATISTICS where TABLE_NAME like "mrg_tbl%"

Notice that it adds a row for mrg_tbl2 with ROWS_READ=3, ROWS_CHANGED=0.

These are our busiest tables and I really wanted to see statistics for them

[Stewart Smith (stewart)]

Setting to Low priority, unlikely to be looked at soon unless is customer request to fix sooner.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-1852