One of my friends, who is a DBA, commented that mixing MyISAM and InnoDB is fairly common among the DBA community, while designing schema in MySQL.
My question is, if this is true, then how good it is? Does it have any effect in the maintainability, scalability etc?
There are generally very few good reasons remaining to use MyISAM. Newer versions of MySQL (5.5+) have extended InnoDB to support all the features that were previously only available on MyISAM (such as fulltext and geospatial indexing), and InnoDB performance is usually considerably better than MyISAM when configured properly.
Unless you are working with an older version of MySQL, or if you have a very good reason for doing so, I'd recommend just using InnoDB throughout any new database design.
IMHO, this is one of the terrible things about MySQL: that it makes you choose between speed and full-text indices (MyISAM) and referential integrity and transactions (InnoDB). If you can, I highly recommend switching to PostgreSQL: in addition to a number of other advantages, you get speed, full-text indices, transactions, and referential integrity in one storage engine. (I no longer use MySQL for new projects at all.)
If you must stick with MySQL, I recommend using InnoDB on all tables unless you have a particular reason not to.
On a practical note.
I have done it a number of times. Notably on one system where queries were locking a whole table as myisam and we converted a number of the critical tables to innodb so they locked at the row level. This removed some bottlenecks from the process and i was with the company for another 18 months after this change with no problems from that solution. The application being supported made fairly intensive use of the database as well so any inadequacies tended to come to light quite quickly.
Related
I read that Innodb is better to use on a table that get a lot's of insert records simultaneously. My application gets about 50 records per seconds. So for these tables should I use Innodb, right?
In the other hand i have some tables that are only used for select, they get few updated or have few new insert. Is MyIsam faster for select ?
If it's the case, is it better to leave some table with MyIsam and some with Innodb or should i use all tables with the same engine ?
My application also searches a lot on the tables that i want to pass in Innodb. What should i do ?
you can check these:
Reasons to use MyISAM:
Tables are really fast for select-heavy loads
Table level locks limit their scalability for write intensive multi-user environments.
Smallest disk space consumption
Fulltext index
Merged and compressed tables.
Reasons to use InnoDB:
ACID transactions
Row level locking
Consistent reads – allows you to reach excellent read write concurrency.
Primary key clustering – gives excellent performance in some cases.
Foreign key support.
Both index and data pages can be cached.
Automatic crash recovery – in case MySQL shutdown was unclean InnoDB tables will still
recover to the consistent state- No check repair like MyISAM may require. All updates have to pass through transactional engine in
InnoDB, which often decreases - performance compared to
non-transactional storage engines.
quoted from here
and for the last part:
REMEMBER! It's OK to mix table types in the same database! In fact it's recommended and frequently required. However, it is important to note that if you are having performance issues when joining the two types, try converting one to the other and see if that fixes it. This issue does not happen often but it has been reported.
quoted from here
I hope that's enough :D
Yes you can, but I'd go with InnoDB only unless there is some serious performance bottleneck
same question on SO
MySQL forum
In short yes you can mix and match to your hearts content.
Keep the following in mind:
InnoDB is ACID complaint. Thus is you need any ACID features use InnoDB. MyISAM is does not support a lot of things like foreign key constraints for example.
Now speed is hard to quantify exactly. Depending on execution paths you might get very big or very small speed differences.
Test and check there is no right or wrong answer here.
I'm currently doing research on the best ways to provide an advanced search for my php project.
I have narrowed it down to using FULLTEXT search rather than using LIKE to find matching strings in a table row. However, to do this it appears I need to sacrifice using the InnoDB engine which will make me lose the ACIDity of transactions and table relationships.
Is it really worth using the MYISAM mysql engine or are there better ways of providing search functionality.
Any pointers would be appreciated!
It really depends on the application... Using MyISAM for anything that needs referential integrity is an instant fail. At the same time, it's text search isn't all that efficient.
Basically, there are two ways to go. If you find you don't need true referential integrity, consider a NoSQL datastore. MongoDB is a great document store database.
If, on the other hand, you really need referential integrity, but also need fast, indexed full-text searching, you might do better to use Sphinx or Apache Solr to create an indexed cache for full-text search.
Either way, I consider MyISAM to be a legacy datastore. I wouldn't use it on a new project. YMMV.
MyISAM has several drawbacks - lack of transaction support, table-level locks which makes it very slow in heavy read+write load type. Another inconvenience of MyISAM tables - they are not crash safe so you can lost some data in case of unexpected shutdown or power loss on server. However MyISAM is very fast on some queries.
Regarding the FullText search I would suggest to use InnoDB + external search engine like Lucene or Sphinx so you could benefit from both safe and reliable storage engine and fast Full-text queries.
For quick start with InnoDB and Sphinx you can refer to http://astellar.com/2011/12/replacing-mysql-full-text-search-with-sphinx/
MySQL 5.6 supports FULLTEXT indexes with InnoDB (released Feb 2013). See:
http://dev.mysql.com/doc/refman/5.6/en/fulltext-search.html
I have 2 tables in which I want more robustness and fortunately don't require frequent rapid fulls of data and examination.
All other tables would inevitably be MyISAM.
Can I safely use both (I've read a handful of discouragements from this) without fearing bugs or data getting affected by differences between engines?
You CAN but this introduces a number of disadvantages:
Your server tuning will now necessarily be a compromise - you cannot use all the memory for either MyISAM OR InnoDB (NB: This does not apply if they are on different servers)
Replication fails in a number of edge-cases, because if you have a failed transaction which contained changes to some MyISAM tables, it can neither correctly commit it nor roll it back
You still can't back up your server using MVCC, because you'd still not get a consistent snapshot of MyISAM tables
So basically, I'd encourage you to switch wholly to InnoDB. Then you can pretty much forget about MyISAM and not devote resources to it, and get the full benefits of using InnoDB. Anyone who thinks MyISAM is faster is either not tuning InnoDB correctly, or has such small data that who cares.
MyISAM does faster table scans, but if you're doing those on large tables, you have bigger problems.
Yes, you can.
Note that only InnoDB tables support transactions and FOREIGN KEY relationships.
I heard this today during interview for java developer. I had to list some advantages of MyISAM over InnoDB and why it's still being widely used. And they were waiting to hear from me the answer as the title of this question.
As I understand from their own answer: MyISAM doesn't have foreign keys and DB can be easily clustered (one table per server for example). But why can't we simply create InnoDB tables without foreign keys? This explaination sounds strange to me..
There is no silver bullet answer here. You need to know the pros and cons of each before you make a decision on which one you use for any particular application.
InnoDB:
supports FK's
supports transactions
uses a large memory buffer for operation
supports row level locking
But has a much higher maintenance cost -- you really need to tune your memory usage, configure your table files, etc.
MyISAM:
has a bunch of special column features that InnoDB doesn't, like:
full text indexes
spatial columns (I'm pretty sure this doesn't work with InnoDB)
Very fast for primary read/append use cases (table locks for updates, deletes, but not for inserts)
Also typically has faster inserts
caches indexes in memory (key buffer), but relies on the OS to buffer the actual data pages
For example, I'd use InnoDB for things like ecommerce, user databases or anything that I want to use transactions in.
For data warehouses, logging, reporting, etc I'd probably use MyISAM.
I had to list some advantages of MyISAM over InnoDB
FULLTEXT search
...
no, that's it.
(OK, there are some cases where MyISAM is faster than InnoDB, but rarely enough that it's worth putting up with the lack of ACID-compliance. Today the main reason for doing anything with MyISAM is to get fulltext search which is sadly not supported in InnoDB.)
I am not sure if this is no longer true MyISAM is faster than InnoDB for reads.
Also, MyISAM tables are stored in separate files and (from what I can remember) you can actually transport those files to another MySQL database and is easier to backup.
By default InnoDB databases are stored in one huge glob on the file system.
As for why it is still being widely used, I always figured it was because it is the default option. Personally, I still believe that the advantages of InnoDB triumphs MyISAM and MyISAM also has problems with data integrity from my experience.
You certainly could create InnoDB tables without foreign keys, but that is cutting out one of the main advantages of it: referential integrity.
However, since MyISAM isn't built with the intent of referential integrity table keys can be stored differently, and perhaps more efficiently.
There are also some differences in locking and access. InnoDB supports row level locking, whereas MyISAM only supports table-level locking. Depending on the queries you're performing (SELECTS versus INSERTS/UPDATES) this can have a noticeable effect on performance.
You prolly need to read up on the Mysql Peformance blog.
It seems like I will be needing transaction with MySQL and I have no idea how should I manage transactions in Mysql with mixed InnoDB/MyISAM tables, It all seems like a huge mess.
You might ask why would I ever want to mix the tables together... the anwer is PERFORMANCE. as many developers have noticed, InnoDB tables generally have bad performance, but in return give higher isolation level etc...
does anyone have any advice regarding this issue?
I think you are overrating the performance difference between MyISAM and InnoDB. MyISAM is faster in data warehousing situations (such as full table scan reporting, etc..), but InnoDB can actually be faster in many cases with normal OLTP queries.
InnoDB is harder to tune since it has more knobs, but a properly tuned InnoDB system can often have higher throughput than MyISAM due to better locking and better I/O patterns.
Given that you can't have transactions in MyISAM tables, I am not sure what the actual problem is. Any data you need transactions for must be in an InnoDB table and you manage the transactions using whatever access library you are using or with manual SQL commands.
There are definite performance benefits of using exactly one engine.
A server tuned for one engine won't be tuned for the other - both require that you allocate a substantial amount of RAM to its exclusive use - therefore, you can't give them both an optimal amount.
Say you have 8G of ram on your (obviously 64-bit, but still relatively small) database server, you might want to assign about 3/4 of it to your innodb page cache. Alternatively, if you're using MyISAM, you may want about half of it to be your key_buffer. You can't do both.
Pick an engine and use it exclusively. There are ways of getting around performance problems - most of them aren't easy though (i.e. they require redesigning your data structure or your application).
The short answer is that there is no transaction support in MyISAM. If you start a transaction, add or modify data in some InnoDB tables, add or modify data in a MyISAM table, and then you have to rollback, your MyISAM change cannot be removed. To support mixed engines like that, your application has to know that changes to whatever data is stored MyISAM happens "outside" of the transaction.
If you need transactions for some processes, then isolate the data that must be transactionable and put all that data in InnoDB.