October 22, 2014

Checking B+tree leaf nodes list consistency in InnoDB

If we have InnoDB pages there are two ways to learn how many records they contain: PAGE_N_RECS field in the page header Count records while walking over the list of records from infimum to supremum In some previous revision of the recovery tool a short summary was added to a dump which is produced by […]

Benchmarking Percona Server TokuDB vs InnoDB

After compiling Percona Server with TokuDB, of course I wanted to compare InnoDB performance vs TokuDB. I have a particular workload I’m interested in testing – it is an insert-intensive workload (which is TokuDB’s strong suit) with some roll-up aggregation, which should produce updates in-place (I will use INSERT .. ON DUPLICATE KEY UPDATE statements […]

How to recover table structure from InnoDB dictionary

To recover a dropped or corrupt table with Percona Data Recovery Tool for InnoDB you need two things: media with records(ibdata1, *.ibd, disk image, etc.) and a table structure. Indeed, there is no information about the table structure in an InnoDB page. Normally we either recover the structure from .frm files or take it from […]

InnoDB Full-text Search in MySQL 5.6 (part 1)

I’ve never been a very big fan of MyISAM; I would argue that in most situations, any possible advantages to using MyISAM are far outweighed by the potential disadvantages and the strengths of InnoDB. However, up until MySQL 5.6, MyISAM was the only storage engine with support for full-text search (FTS). And I’ve encountered many […]

Logging Foreign Key errors

In the last blog post I wrote about how to log deadlock errors using Percona Toolkit. Foreign key errors have the same problems. InnoDB only logs the last error in the output of SHOW ENGINE INNODB STATUS, so we need another similar tool in order to have historical data. pt-fk-error-logger This is a tool very […]

Innodb Table Locks

Innodb uses row level locks right ? So if you see locked tables reported in SHOW ENGINE INNODB STATUS you might be confused and rightfully so as Innodb table locking is a bit more complicated than traditional MyISAM table locks. Let me start with some examples. First lets run SELECT Query:

As you can […]

Using innodb_sys_tables and innodb_sys_indexes

I was playing with Percona Server today and found fast_index_creation does not work quite exactly like described in the manual. The point I’m looking to make though it would be very hard to catch this problem without additional information_schema tables we added in Percona Server. I was doing simple ALTER TABLE such as: “alter table […]

How to recover deleted rows from an InnoDB Tablespace

In my previous post I explained how it could be possible to recover, on some specific cases, a single table from a full backup in order to save time and make the recovery process more straightforward. Now the scenario is worse because we don’t have a backup or the backup restore process doesn’t work. How […]

STOP: DELETE IGNORE on Tables with Foreign Keys Can Break Replication

DELETE IGNORE suppresses errors and downgrades them as warnings, if you are not aware how IGNORE behaves on tables with FOREIGN KEYs, you could be in for a surprise. Let’s take a table with data as example, column c1 on table t2 references column c1 on table t1 – both columns have identical set of rows for […]

Hijacking Innodb Foreign Keys

I guess I’m first to post in 2012 so Happy New Year all blog readers ! Now back to HardCore MySQL business – foreign Keys. MySQL supported Foreign Keys for Innodb for many years, yet rudimentary support initially added in MySQL 3.23.44 have not been improved in new releases as much as I’d like. We […]