Innodb on FromDual GmbH

MariaDB Foreign Key Constraint example

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 19 Aug 2021 10:35:54 +0000

Foreign Key Constraints are used to model a parent/child relation in an entity relationship (ER) model:

How to force InnoDB Buffer Pool flushing

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 10 Dec 2020 17:38:36 +0000

InnoDB tries to keep pages in Buffer Pool to be fast. If a page is changed by a DML statement (INSERT, UPDATE, DELETE) this change will be done in InnoDB Buffer Pool and not directly on disk. But those changed InnoDB pages residing in InnoDB Buffer Pool must be flushed sooner or later to disk to become persistent. This is done by the InnoDB background writer thread(s) (default 4).

InnoDB full-text index corruption

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 08 Jul 2020 21:52:47 +0000

In a recent customer engagement we experienced a lot of corrupted (normal) indexes and also corrupted full-text indexes on InnoDB tables in a Galera Cluster (v10.4.13).

innodb_deadlock_detect - Rather Hands off!

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 23 Mar 2020 11:24:15 +0000

Recently we had a new customer who has had from time to time massive database problems which he did not understand. When we reviewed the MySQL configuration file (my.cnf) we found, that this customer had disabled the InnoDB Deadlock detection (innodb_deadlock_detect).

InnoDB Page Cleaner intended loop takes too long

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 18 Feb 2020 17:50:55 +0000

Recently we migrated a database system from MySQL 5.7 to MariaDB 10.3. Everything went fine so far just the following message started to pop-up in the MariaDB Error Log File with the severity Note:

InnoDB Log Buffer is too small for large transactions

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 23 Dec 2019 14:05:49 +0000

Your InnoDB Redo Log Buffer is too small for large transactions. Make the InnoDB Redo Log Buffer (innodb_log_buffer_size) bigger if you have enough RAM available to avoid additional I/O.
1 Mibyte is good for databases with small transactions. 8 Mibyte is good for medium size transactions. 64 MiByte is good for large transactions.

Who else is using my memory - File System Cache analysis

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 19 Jul 2019 15:52:32 +0000

Understanding InnoDB - Buffer Pool Flushing

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 08 Apr 2019 20:31:56 +0000

InnoDB Page Cleaner Thread

The InnoDB Page Cleaner Thread is an InnoDB background thread that flushes dirty pages from the InnoDB Buffer Pool to disk. Prior MySQL 5.6 this action was performed by the InnoDB Master Thread.

UNDO logs in InnoDB system tablespace ibdata1

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 05 Dec 2018 21:55:36 +0000

We see sometimes at customers that they have very big InnoDB system tablespace files (ibdata1) although they have set innodb_file_per_table = 1.

How to move InnoDB-Logfiles on a Galera Cluster

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 05 Oct 2016 10:35:35 +0000

Somebody recently asked, what they had to do, if they wanted to move their InnoDB-Logfiles back to the datadir. As a challenge, the servers were part of a Galera Cluster.

InnoDB plugin is enabled

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Jul 2015 20:16:36 +0000

InnoDB plugin is enabled.

InnoDB Log File size is too small

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Jul 2015 20:15:36 +0000

The InnoDB Log File (innodb_log_file_size) size is possibly too small.
Choosing a too small InnoDB Log File size can have significant write performance impacts.

InnoDB Foreign Key error detected

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Jul 2015 20:14:36 +0000

MySQL (InnoDB, PBXT, NDB, TokuDB) support Foreign Keys to show relatations between tables. Those relations can be enforced through Foreign Key Constraints.

InnoDB Force Recovery is enabled

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Jul 2015 20:12:36 +0000

InnoDB Force Recovery (innodb_force_recovery) is enabled. This mode should be used for data recovery purposes only. It prohibits writing to the data.

InnoDB Flush Log at Transaction Commit

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Jul 2015 20:11:36 +0000

InnoDB Flush Log at Transaction Commit is set to a values != 1. This can lead to a loss of committed transactions in case of a power failure or an unclean shutdown of your database.

InnoDB Deadlock detected

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Jul 2015 20:10:36 +0000

You got an InnoDB Deadlock. Please talk to your development department to fix this problem. Deadlocks are an application problem!

InnoDB Buffer Pool Instances is too small

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Jul 2015 20:09:36 +0000

If you are using MariaDB/MySQL 5.5 and newer you should use several InnoDB Buffer Pool Instances for performance reasons.
Some rules to size InnoDB Buffer Pool instances are:

InnoDB Flush Method has changed

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 01 Jul 2015 10:34:36 +0000

The InnoDB Flush Method has changed. This can have an impact on InnoDB write Performance.

innodb_checkpoint_age in plain MySQL?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sat, 27 Dec 2014 15:45:00 +0000

In Percona Server we have a STATUS variable indicating roughly possible recovery time:

How to recover deleted tablespace?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 14 Nov 2014 22:56:17 +0000

Sometimes, MySQL tablespace file(s) might be deleted by mistake, e.g. delete the shared tablespace (ibdata1) or an individual tablespace (table_name.ibd).

Get rid of wrongly deleted InnoDB tables

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 22 Oct 2014 22:10:58 +0000

Precaution: Before you try this out on your production system do a BACKUP first! FromDual Backup Manager can help you with this.

Switching from MySQL/MyISAM to Galera Cluster

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 12 Mar 2013 08:23:36 +0000

Switching from MySQL/MyISAM to Galera Cluster requires that all tables (except those from the mysql, information_schema and performance_schema) are using the InnoDB Storage Engine.

Shrinking InnoDB system tablespace file ibdata1 PoC

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sat, 08 Dec 2012 13:43:11 +0000

In this weeks MySQL workshop we were discussing, beside other things, about the innodb_file_per_table parameter and its advantages of enabling it. In addition there was a discussion if the InnoDB system tablespace file can be shrinked once it has been grown very large or not. We all know the answer: The InnoDB system tablespace file does never shrink again.

Deadlocks, indexing and Primary Key's

oli.sennhauser@fromdual.com (Oli Sennhauser) — Thu, 16 Aug 2012 10:51:40 +0000

Recently a customer has shown up with some deadlocks occurring frequently. They were of the following type (I have shortened the output a bit):

InnoDB variables and status explained

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 02 Jul 2012 17:07:32 +0000

InnoDB Buffer Pool

The InnoDB Buffer Pool is the memory area where the InnoDB Storage Engine caches its data and index blocks. Each InnoDB data and index block has a size of Innodb_page_size (16384 byte = 16 kbyte). The InnoDB Buffer Pool is configured in bytes with the innodb_buffer_pool_size variable. On a dedicated system the InnoDB Buffer Pool can be configured up to 80% of the systems physical RAM (free).

Change MyISAM tables to InnoDB and handle SELECT COUNT(*) situation

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 12 Jun 2012 20:48:38 +0000

Its a known problem that changing the Storage Engine from MyISAM to InnoDB can cause some problems
[ 1
] if you have queries of this type:

Does InnoDB data compression help with short disk space?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 23 Mar 2012 18:35:29 +0000

Because we are a bit short off disk space on one of our servers I had the idea to try out the MySQL feature Data Compression for InnoDB. This feature is useful if you have tables with VARCHAR, BLOB or TEXT attributes.

Codership partners with FromDual to offer consulting and support services for Galera Cluster for MySQL

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sun, 19 Feb 2012 09:56:45 +0000

Helsinki, Finland, Uster, Switzerland – February 18, 2012 – Codership, the provider of Galera Cluster for MySQL, and FromDual, a MySQL consulting company, today announced collaboration to offer Galera Cluster technology and related support and consulting services for Galera users all over the world, especially in German speaking countries Germany, Austria and Switzerland (DACH). Galera Cluster is a synchronous, true multi-master replication cluster for MySQL using the well known InnoDB storage engine. Customers can deploy Galera Cluster locally in LAN environments, as geo-clusters over the WAN or as virtual cluster in the cloud.

Recover lost .frm files for InnoDB tables

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 20 Dec 2011 22:51:03 +0000

Recently I found in a forum the following request for help:

How MySQL behaves with many schemata, tables and partitions

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 30 Nov 2011 15:35:28 +0000

Introduction

Recently a customer claimed that his queries were slow some times and sometimes they were fast.

Galera - Synchronous Multi-Master Replication Cluster for MySQL/InnoDB

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 23 Sep 2011 11:07:03 +0000

Galera features

Galera provides the following features:

Synchronous replication
Active/active multi-master topology
Read and write to any cluster node
Automatic membership control, failed nodes drop from the cluster
Automatic node joining
True parallel row level replication
Direct client connections
Drop-in replacement for native MySQL

Galera benefits

Benefits using Galera Replication:

How good is MySQL INSERT TRIGGER performance

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 03 Aug 2011 17:08:36 +0000

Abstract: In this article we discuss how big is the performance impact of MySQL TRIGGERs compared to application side logging (with INSERT) into a MySQL table.

ER-Diagram of the InnoDB Data Dictionary

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 29 Jul 2011 17:37:30 +0000

With the new MySQL 5.6 release there are some more InnoDB Data Dictionary Tables in the INFORMATION_SCHEMA:

Warming up the InnoDB Buffer Pool during start-up

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 22 Jul 2011 17:12:51 +0000

Abstract: Heating up the InnoDB Buffer Pool during the MySQL instance startup should significantly improve InnoDB Performance in the beginning of the life of the Instance. This is achieved by sequential scans of the needed data instead of random I/O reads which would happen when we just let the system work it out by itself.
How to find the database objects which can be loaded during MySQL start-up and how to load them automatically is described in this article.

InnoDB Graphs for MySQL Performance Monitor

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 14 Jun 2011 10:41:49 +0000

We have just released v0.7.1 of the FromDual MySQL Performance Monitor. The new release can be downloaded from here.

How can I find what InnoDB version I am using?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sat, 01 Jan 2011 12:05:22 +0000

In the old days everything was simpler. We had one maker of our favourite database management system and possibly the choice between different Storage Engines. Mostly the decision has to be taken between MyISAM and InnoDB. When you care about your data integrity you have chosen InnoDB.

Disadvantages of explicitly NOT using InnoDB Primary Keys?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 20 Sep 2010 15:36:36 +0000

We recently had the case with one of our customers where we got externally generated random hash values (up to 70 bytes) and they were used as Primary Keys in InnoDB.

Which table is hit by an InnoDB page corruption?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 02 Aug 2010 17:49:38 +0000

InnoDB is known to have crash-recovery capabilities and thus is called a crash safe storage engine (in contrary to MyISAM). Nevertheless under certain circumstances it seems like InnoDB pages can get corrupt during a crash and then a manual crash-recovery is needed.

MySQL hints

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 15 Mar 2010 13:38:54 +0000

MySQL Questions & Answers

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 15 Mar 2010 11:15:25 +0000

Search with special characters

This Question has been moved to the Forum.

What is CHECK TABLE doing with InnoDB tables?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 29 Jan 2010 21:37:00 +0000

Recently we had a case where a customer got some corrupted blocks in his InnoDB tables. His largest tables where quite big, about 30 to 100 Gbyte. Why he got this corrupted blocks we did not find out yet (disk broken?).

MariaDB has broken the concept of dynamically configurable buffer pools!

oli.sennhauser@fromdual.com (Oli Sennhauser) — Mon, 09 Feb 2026 19:14:00 +0100

Problem description

MySQL introduced the dynamically configurable InnoDB buffer pool with 5.7.5 in September 2014 (here and here):