MyISAM versus InnoDB [closed]

Answer 1

A bit late to the game...but here's a quite comprehensive post I wrote a few months back, detailing the major differences between MYISAM and InnoDB. Grab a cuppa (and maybe a biscuit), and enjoy.

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The major difference between MyISAM and InnoDB is in referential integrity and transactions. There are also other difference such as locking, rollbacks, and full-text searches.

Referential Integrity

Referential integrity ensures that relationships between tables remains consistent. More specifically, this means when a table (e.g. Listings) has a foreign key (e.g. Product ID) pointing to a different table (e.g. Products), when updates or deletes occur to the pointed-to table, these changes are cascaded to the linking table. In our example, if a product is renamed, the linking table’s foreign keys will also update; if a product is deleted from the ‘Products’ table, any listings which point to the deleted entry will also be deleted. Furthermore, any new listing must have that foreign key pointing to a valid, existing entry.

InnoDB is a relational DBMS (RDBMS) and thus has referential integrity, while MyISAM does not.

Transactions & Atomicity

Data in a table is managed using Data Manipulation Language (DML) statements, such as SELECT, INSERT, UPDATE and DELETE. A transaction group two or more DML statements together into a single unit of work, so either the entire unit is applied, or none of it is.

MyISAM do not support transactions whereas InnoDB does.

If an operation is interrupted while using a MyISAM table, the operation is aborted immediately, and the rows (or even data within each row) that are affected remains affected, even if the operation did not go to completion.

If an operation is interrupted while using an InnoDB table, because it using transactions, which has atomicity, any transaction which did not go to completion will not take effect, since no commit is made.

Table-locking vs Row-locking

When a query runs against a MyISAM table, the entire table in which it is querying will be locked. This means subsequent queries will only be executed after the current one is finished. If you are reading a large table, and/or there are frequent read and write operations, this can mean a huge backlog of queries.

When a query runs against an InnoDB table, only the row(s) which are involved are locked, the rest of the table remains available for CRUD operations. This means queries can run simultaneously on the same table, provided they do not use the same row.

This feature in InnoDB is known as concurrency. As great as concurrency is, there is a major drawback that applies to a select range of tables, in that there is an overhead in switching between kernel threads, and you should set a limit on the kernel threads to prevent the server coming to a halt.

Transactions & Rollbacks

When you run an operation in MyISAM, the changes are set; in InnoDB, those changes can be rolled back. The most common commands used to control transactions are COMMIT, ROLLBACK and SAVEPOINT. 1. COMMIT - you can write multiple DML operations, but the changes will only be saved when a COMMIT is made 2. ROLLBACK - you can discard any operations that have not yet been committed yet 3. SAVEPOINT - sets a point in the list of operations to which a ROLLBACK operation can rollback to

Reliability

MyISAM offers no data integrity - Hardware failures, unclean shutdowns and canceled operations can cause the data to become corrupt. This would require full repair or rebuilds of the indexes and tables.

InnoDB, on the other hand, uses a transactional log, a double-write buffer and automatic checksumming and validation to prevent corruption. Before InnoDB makes any changes, it records the data before the transactions into a system tablespace file called ibdata1. If there is a crash, InnoDB would autorecover through the replay of those logs.

FULLTEXT Indexing

InnoDB does not support FULLTEXT indexing until MySQL version 5.6.4. As of the writing of this post, many shared hosting providers’ MySQL version is still below 5.6.4, which means FULLTEXT indexing is not supported for InnoDB tables.

However, this is not a valid reason to use MyISAM. It’s best to change to a hosting provider that supports up-to-date versions of MySQL. Not that a MyISAM table that uses FULLTEXT indexing cannot be converted to an InnoDB table.

Conclusion

In conclusion, InnoDB should be your default storage engine of choice. Choose MyISAM or other data types when they serve a specific need.

Answer 2

I tried to run insertion of random data into MyISAM and InnoDB tables. The result was quite shocking. MyISAM needed a few seconds less for inserting 1 million rows than InnoDB for just 10 thousand!

Answer 3

In my experience, MyISAM was a better choice as long as you don't do DELETEs, UPDATEs, a whole lot of single INSERT, transactions, and full-text indexing. BTW, CHECK TABLE is horrible. As the table gets older in terms of the number of rows, you don't know when it will end.

Answer 4

People often talk about performance, reads vs. writes, foreign keys, etc. but there's one other must-have feature for a storage engine in my opinion: atomic updates.

Try this:

1. Issue an UPDATE against your MyISAM table that takes 5 seconds.
2. While the UPDATE is in progress, say 2.5 seconds in, hit Ctrl-C to interrupt it.
3. Observe the effects on the table. How many rows were updated? How many were not updated? Is the table even readable, or was it corrupted when you hit Ctrl-C?
4. Try the same experiment with UPDATE against an InnoDB table, interrupting the query in progress.
5. Observe the InnoDB table. Zero rows were updated. InnoDB has assured you have atomic updates, and if the full update could not be committed, it rolls back the whole change. Also, the table is not corrupt. This works even if you use killall -9 mysqld to simulate a crash.

Performance is desirable of course, but not losing data should trump that.

Answer 5

I have briefly discussed this question in a table so you can conclude whether to go with InnoDB or MyISAM.

Here is a small overview of which db storage engine you should use in which situation:

                                                 MyISAM   InnoDB
----------------------------------------------------------------
Required full-text search                        Yes      5.6.4
----------------------------------------------------------------
Require transactions                                      Yes
----------------------------------------------------------------
Frequent select queries                          Yes      
----------------------------------------------------------------
Frequent insert, update, delete                           Yes
----------------------------------------------------------------
Row locking (multi processing on single table)            Yes
----------------------------------------------------------------
Relational base design                                    Yes

Summary

• In almost all circumstances, InnoDB is the best way to go
• But, frequent reading, almost no writing, use MyISAM
• Full-text search in MySQL <= 5.5, use MyISAM

Answer 6

myisam is a NOGO for that type of workload (high concurrency writes), i dont have that much experience with innodb (tested it 3 times and found in each case that the performance sucked, but it's been a while since the last test) if you're not forced to run mysql, consider giving postgres a try as it handles concurrent writes MUCH better