What's new in MySQL 5.6

Seminar:
What's new in MySQL 5.6?

Presenter: Shlomi Noach
Oracle ACE
MySQL Community Member
http://openark.org

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copyright (c) 2012 Shlomi Noach

The state of MySQL 5.6
●
MySQL 5.6 is being under development
since early 2011
●
Uses a milestone based release model:
milestone features are assumed to have
RC quality
●
5.6.7 (Release Candidate) recently
announced

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The state of MySQL 5.6
● While 5.5 (first release under Oracle's stewardship)
was focused on performance, scale up and integrity,
and had little focus on new features, 5.6 offers:
– Loads of new usability features
– Major improvements to InnoDB architecture
– Optimizer enhancements
– Major replication improvements
– PERFORMANCE_SCHEMA: dozens new tables

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New in MySQL 5.6
● We discuss new & noteworthy under the
following:
– InnoDB
– Replication
– Optimizer
– Partitioning

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InnoDB
● Once acquired both InnoBase and Sun
Microsystems, Oracle directed more
resources at InnoDB development as
integral part of MySQL
● InnoDB is today the default storage engine
for MySQL
● 5.6 brings new usability, maintainability
and performance improvements to InnoDB

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InnoDB: online DDL
● Arguably the #1 reason one would want to
upgrade to 5.6
● InnoDB now supports online, non-blocking
ALTER TABLE operations for many DDL
statements:
– ADD/MODIFY/DROP COLUMN, ADD/DROP INDEX,
ADD/DROP Foreign Keys, change of
AUTO_INCREMENT, change of row format,
compression, and more.
http://dev.mysql.com/doc/refman/5.6/en/innodb-online-ddl.html

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InnoDB: FULLTEXT
● FULLTEXT indexes now available on InnoDB
● Support same syntax as with MyISAM
– Boolean search
– Stopwords
– Proximity
● Fills the last gap for MyISAM users to migrate to
InnoDB
http://dev.mysql.com/doc/refman/5.6/en/innodb-table-and-index.html#innodb-fulltext-index

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InnoDB: Transportable tables
● “move around” InnoDB tables by copying them via
file system
● Allows for fast table duplicate; fast export of table
between servers
● via:
– FLUSH TABLES … FOR EXPORT
– ALTER TABLE … DISCARD TABLESPACE
– ALTER TABLE … IMPORT TABLESPACE
http://blogs.innodb.com/wp/2012/04/innodb-transportable-tablespaces/

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InnoDB: NoSQL access
● It is possible to access InnoDB via memcache API
– Uses embedded memcached server
– Via standard memcache clients
– No need for SQL, avoids parsing, preparing, QEP evaluation
● However fully utilizing transactions; ACID compliant!
– At current supporting single table
– memcache writes batched; may require READ
UNCOMMITED on SQL side
http://dev.mysql.com/doc/refman/5.6/en/innodb-memcached.html

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InnoDB: performance
● InnoDB 5.6 performance improvements include:
– Preloading buffer pool (cache flush to disk)
– Adaptive REDO logs flushing
– Better, more concurrent buffer flushing
– Configurable tablespace location
– UNDO logs on separate tablespace
– Persistent stats
– More...

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Partitions
● Introduced in 5.1
● Features RANGE, LIST, HASH & KEY partitioning
– 5.1 RANGE and LIST limited to integer partitioning keys
● 5.5 introduced:
– RANGE COLUMNS and LIST COLUMNS partitioning,
removing said limitation
– ALTER TABLE … TRUNCATE PARTITION
● 5.6 boasts major partition improvements

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Partition exchange
● Swap a partition with a table of the exact
same structure
– Either or both may contain data
– Allows for quick insertion or extraction of data
into/from partitioned table
● via:
ALTER TABLE part_tbl
EXCHANGE PARTITION part_name WITH TABLE tbl;
http://dev.mysql.com/doc/refman/5.6/en/partitioning-management-exchange.html

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Explicit partition selection
● Limit a DML statement to a specific partition or set
of partitions
– Similar to partition pruning, but manual, and applies for
SELECT, UPDATE, INSERT, REPLACE, DELETE,
LOAD
– Avoid partition lookup on complex search terms, or
otherwise based on known heuristic
● via:
UPDATE tbl PARTITION (p2, p3, p5) SET c=1 WHERE
condition_holds
http://dev.mysql.com/doc/refman/5.6/en/partitioning-selection.html

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Partitions: lock pruning
● Ever since partitions were introduced in 5.1, locking has
been an issue
● Even with partition pruning, locks were held over all table
partitions
– And although InnoDB uses row-level locking and is supposedly
unaffected by table locks, the lock mechanism is still invoked
– This caused for a known scenario of reduced performance on
intensive INSERTs to a partitioned table
● With 5.6 this is alleviated; locks are expected to be
placed only on relevant partitions.
http://dev.mysql.com/doc/refman/5.6/en/partitioning-limitations-locking.html

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Execution plans
● Query Execution Plan (QEP) is boosted in
5.6 both internally (optimized plans) and
usability-wise
● Some notorious limitations are removed,
and infamous QEP scenarios now fixed

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Execution plans: subqueries
● Up till 5.5, subqueries & derived tables:
– Evaluated as non-indexed temporary tables
– Would, in common scenarios, re-evaluate throughout the query
●
select * from actor where actor_id in
(select actor_id from film_actor where film_id = 7)
●
5.6 introduces:
– Indexes on derived tables
– Semijoins avoid re-evaluation and skip execution phases
https://dev.mysql.com/doc/refman/5.6/en/semi-joins.html

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Execution plans: indexes
●
Index optimizations include:
– Index condition pushdown: better execution plans
for queries where index can satisfy conditions
●
This reduces MySQL-SE data transfer and allows for
storage engine internal handling of conditions.
– Improved index merge
https://dev.mysql.com/doc/refman/5.6/en/index-condition-pushdown-optimization.html

http://dev.mysql.com/doc/refman/5.6/en/index-merge-optimization.html

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Execution plans: EXPLAIN
● EXPLAIN will now work on INSERT,
UPDATE & DELETE statements
– Previously only on SELECT
– Hacks used to convert UPDATE/DELETE
statements into SELECT statements so as to
guess QEP. The result was not authoritative.
http://dev.mysql.com/doc/refman/5.6/en/explain.html

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Execution plans: EXPLAIN
● EXPLAIN FORMAT=JSON is introduced
– Presenting execution plan in a JSON-tree format
– Much more accurate output than EXPLAIN
– Easy to parse and diagnose by automated tools
● Optimizer trace presents with actual execution steps
taken after fact
– Also in JSON format
http://dev.mysql.com/doc/internals/en/optimizer-tracing.html

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Replication
● New replication features make for:
– Faster replication
– Safer replication
– Easier to maintain replication

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Replication: GTID
● Global Transaction IDs are introduced into the binary logs,
such that every statement has a globally unique ID
● A slave can connect to its master and auto-detect binlog
position via GTID
● Easier to failover to another slave, or to move slaves along
replication tree
● via:
CHANGE MASTER TO MASTER_AUTO_POSITION = 1
http://dev.mysql.com/doc/refman/5.6/en/replication-gtids.html

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Multithreaded slaves
● Based on a thread-per-database
– Assumes different schemas completely unrelated
● Multithreaded replication breaks the years-old
“single threaded slave” paradigm
– In this paradigm a slave had to do all master's work
utilizing one thread only
– Very quickly leads to replication lag issues
https://blogs.oracle.com/MySQL/entry/benchmarking_mysql_replication_with_multi

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Crashsafe replication
● “Standard” replication uses master.info and relay-
log.info files to manage records of current
replication status
– These files not flushed to disk upon update
– Cause for replication break (or worse – integrity loss)
● With 5.6, replication status can be written to system
InnoDB tables
– Being transactional, these are fully ACID
http://mysqlmusings.blogspot.co.il/2011/04/crash-safe-replication.html

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Replication: more
● Time delayed replication available via
CHANGE MASTER TO MASTER_DELAY=...
● Binary log checksums allow for safer log transfer between
hosts
● New set of utilities allows for easier replication maintenance
● Optimized row-based replication: only transfer actual row
changes, not complete changed row
http://dev.mysql.com/tech-resources/articles/mysql-5.6-replication.html

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Thank you!
● I blog at http://openark.org
● Free and open source projects:
– common_schema: DBA's framework for
MySQL
– openark-kit: common utilities for MySQL
– mycheckpoint: lightweight, SQL oriented
monitoring for MySQL
● shlomi[at]openark.org

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