In the 5.6.4 release it is now possible to create an InnoDB database with 4k or 8k page sizes in addition to the original 16k page size. Previously, it could be done by recompiling the engine with a different value for UNIV_PAGE_SIZE_SHIFT and UNIV_PAGE_SIZE. With this release, you can set –innodb-page-size=n when starting mysqld, or put innodb_page_size=n in the configuration file in the [mysqld] section where n can be 4k, 8k, 16k, or 4096, 8192, 16384.

The support of smaller page sizes may be useful for certain storage media such as SSDs. Performance results can vary depending on your data schema, record size, and read/write ratio. But this provides you more options to optimize your performance.

When this new setting is used, the page size is set for all tablespaces used by that InnoDB instance. You can query the current value with;

SHOW

In April of 2011, InnoDB team published the early access of NoSQL to InnoDB with memcached, plus several new features as part of MySQL 5.6.2 milestone release. This week, we announced additional early access to new InnoDB features for the community to test, and provide feedback.

There are two release packages from InnoDB team on MySQL Labs: InnoDB full-text search, and InnoDB new features.

InnoDB Full-Text Search

MySQL 5.5 makes InnoDB the default storage engine, so everyone can benefit from ACID-compliant transactions, referential integrity, crash recovery.  However, some users need InnoDB to have built-in full-text

The InnoDB full-text search capability is an exciting feature. The full-text search itself is generally useful to have in an RDBMS. If an application is using all InnoDB tables except for one that is used for full-text searches, now that last table can be switched to InnoDB. If putting the full-text data in a MyISAM table led to scalability problems, duplication, or a less-than-ideal schema design, now those issues can be addressed.

In this post, I’ll take you through some of the basics of setting up and querying an InnoDB FULLTEXT search index. I’ll leave the scalability and performance aspects to Jimmy’s and Vinay’s blog posts, and just use some toy-sized data for

Introduction

The InnoDB  UNDO entries reside in a special system table called the UNDO log. This log is made up of several segments. These segments are called rollback segments. A segment in InnoDB is similar to what a file would be in a file system,e.g., user tables and indexes are also stored as separate segments within the same tablespace,  only their format is different. In that sense there is nothing special about InnoDB UNDO logs. This feature allows storing of the UNDO log across several tablespaces.

Purpose

UNDO logs  contain the before image of modified records. There are two types of UNDO records, one for insert and another for updates. The insert UNDO records can be discarded on transaction rollback. The update records are used for rollback, MVCC and by purge. It is because of

One of the features found in the summer 2011 labs release is the ability to select the InnoDB page size without recompiling.  Smaller page sizes may be useful for certain storage media such as SSDs where there is no need to minimize seek time between reads.

A new global setting called innodb-page-size can be set to 4k, 8k or 16k before creating a new MySQL instance. This sets the page size for all tablespaces used by that InnoDB instance.   This can be done in my.cnf or on the mysqld command line.  It is a read-only variable while the engine is running since it must be set before InnoDB starts up and creates a new system tablespace.  That happens when InnoDB does not find ibdata1 in the data directory.  If your system tablespace already exists using one page size and innodb-page-size is something else, the engine will not start.

A few bugs were found

For those interested in InnoDB internals, this post tries to explain why the global kernel mutex was required and the new mutexes and rw-locks that now replace it. Along with the long term benefit from this change.

InnoDB’s core sub-systems up to v5.5 are protected by a global mutex called the Kernel mutex. This makes it difficult to do even some common sense optimisations. In the past we tried optimising the code but it would invariably upset the delicate balance that was achieved by tuning of the code that used the global Kernel mutex, leading to unexpected performance regression. The kernel mutex is also abused in several places to cover operations unrelated to the core e.g., some counters in the server thread main loop.

The InnoDB core sub-systems are:

Background

InnoDB gathers statistics for the data in user tables, which are used by the MySQL optimizer to choose the best query plan. For a long time the imprecision and instability of these statistics have been creating problems for users.

The problem is that these statistics are recalculated at any of the following events:

* When the table is opened

* When the table has changed a lot (1/16th of the table has been updated/deleted or inserted)

* When ANALYZE TABLE is run

* When SHOW TABLE STATUS or SHOW INDEX FROM is run

* When InnoDB Monitor is turned ON

* others

and so their recalculation must be quick an unnoticeable. Thus the quick algorithm just picks 8 random

One of the most important things a database user or DBA wants to know is what columns, indexes etc. a table has. There are a few ways to find these things out, such as show tables. However, to really reveal all of the detailed metadata information in an InnoDB database, many have tried the “innodb_table_monitor” to peek into internal data dictionary. By creating an “innodb_table_monitor” table, InnoDB will print out the contents of metadata periodically. Unfortunately, it is printed out in an unstructured text for each table, and to find out what you need you would have to either carefully scan the output or have your own parser to do some additional analysis on the result if you want to display them systematically.

Well, in the MySQL 5.6 release, “innodb_table_monitor” can become history, and you will no longer need to search the text

In MySQL 5.6.2 we have introduced a new background thread named the page_cleaner in InnoDB. Adaptive flushing of modified buffer pool pages in the main background thread, async flushing by a foreground query thread if the log files are near to wrapping around, idle flushing and shutdown flushing are now moved to this thread, leaving only the last resort sync flushing in foreground query threads. We’ve also added counters for these activities.

As page_cleaner is all about the flushing of dirty pages to disk it’ll do you a world of good if you can go through this post where I have explained different types of flushing that happen inside InnoDB and the conditions that trigger flushing. The page_cleaner thread is only concerned with flush_list flushing (this may change

In MySQL 5.6 we’ve added a new feature that closes and unloads table instances from the InnoDB internal data dictionary, once a user configurable threshold is reached. This ends the situation where you could have hundreds of megabytes caching rarely used entries until the server was restarted and will be particularly appreciated by hosting and software as a service providers.

For this we’ve used an existing MySQL config variable table-definition-cache.  This cache limit is a soft limit. This means that if the user has more than table-definition-cache tables open then InnoDB will

Data Dictionary Language (DDL) operations have traditionally been slow in MySQL. Any change to the table definition would be implemented by creating a copy of the table and index layout with the requested changes, copying the table contents row by row, and finally renaming tables and dropping the original table.

The InnoDB Plugin for MySQL 5.1 implements a more efficient interface for creating and dropping indexes. Indexes can be created or dropped without rebuilding the entire table.

Speeding up Bulk INSERT, UPDATE and DELETE Operations

Normally, InnoDB would update all indexes of a table when rows are inserted or deleted. If you update an indexed column, InnoDB would have to delete the old value and insert the new value in the corresponding index. If you update a primary key column, the row would be deleted and inserted

To speed up bulk loading of data, InnoDB implements an insert buffer, a special index in the InnoDB system tablespace that buffers modifications to secondary indexes when the leaf pages are not in the buffer pool. Batched merges from the insert buffer to the index pages result in less random access patterns than when updating the pages directly. This speeds up the operation on hard disks.

In MySQL 5.5, the insert buffer has been extended to a change buffer, which covers all modifications of secondary index leaf pages. This will improve the performance of bulk deletes and updates, transaction rollback and the purging of deleted records (reducing the “purge lag”).

To assess the benefits of the extended buffering, you may want to run benchmarks with the settings innodb_change_buffering=all, innodb_change_buffering=inserts, and