MySQL comes with different level of support for InnoDB Storage engine for every version of its release. The Default configuration settings for InnoDB also varies version wise. So its always a wise decision to ensure that if we are upgrading the MySQL and are having InnoDB as default Storage engine, then it does no harm to revisit the configuration settings.
InnoDB is default general purpose storage engine and is recommended for all tables unless you have any special cases. MySQL Server has a pluggable storage engine architecture that enables storage engines to be loaded into and unloaded from a running MySQL server.
InnoDB has below features that separates it from other engine types,
- Row level Locking – blocks reading or writing of table data by connections if another connection is currently using that data.(MyISAM has table level locks) .
- Acid Compliance – Atomicity means that if a transaction fails then the changes are rolled back and not committed. Consistency means that each successfully executed transaction will move the database ahead in time from one state to the next in a consistent manner without errors or data integrity issues. Isolation means that each transaction will see separate sets of data in time and not conflict with other transactional data access.Durability ensures that any data that has been committed in a successful transaction will be written to disk in its final state, without the risk of data loss from errors or system failure, and will then be available to transactions that come in the future. So chances of transaction corruption is not possible or very small.All transactions are executed in isolations.
- Referential Integrity – It has ability to store data in multiple tables and maintain referential integrity and data consistency.
One can verify the type of engine used by MySQL by issuing below commands,(I have PhpMyAdmin and it looks something like below screenshot)
Also before creating any tables with InnoDB as engine, it makes sense to check transaction isolation levels. This can be checked with below command,
Transaction Isolation levels has of below options,
READ UNCOMMITTED - Every select query operates without locks so you don’t get consistency and might contain dirt reads. So it violates ACID Principles and should never be used if your application issues transactions that require point-in-time consistent data reads.
READ COMMITTED – This setting offer consistent reads without table or row locks. Each consistent read, even within the same transaction, sets and reads its own fresh snapshot of point-in-time data.It offers consistency and performance for applications that do not require full ACID.It does not fully comply with ACID.
REPEATABLE READ – The InnoDB default isolation level for ACID compliance.
SERIALIZABLE: This is the same as REPEATABLE READ but MySQL converts select queries with the preface of LOCK IN SHARED MODE when auto-commit is enabled. If auto-commit is disabled then each select query is started in a separate transaction, which will ensure that all reads are consistent. This setting also allows for XA distributed transactions support, which you can read more about in the MySQL manual.The SERIALIZABLE value setting will impact database transaction execution performance, so only enable this if it is absolutely necessary.
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