I have a myISAM table with 2.5 million and rising rows. It is myisam as I require FullText searching.
Having done some research on stackoverflow I'm looking into creating the table again as a InnoDB table and then creating a copy in myISAM. Then I will create triggers which will replicate any changes in the innodb table to the myisam table.
The innodb table will function better as it works transactionally and doesn't lock the whole table when it is written to or updated.
My question is: Will I see much benefit in the myisam table as surely it is going to be written to as often as before because every write to the innodb table will result in a subsequent write to the myisam.
Any suggestions, or other ideas gratefully received.
Brett
Using triggers to copy from MyISAM to InnoDB has the risk of creating inconsistent data, when transactions are rolled back.
A better idea might be to install a full text search engine like Sphinx that can work with InnoDB tables.
Another idea would be to synchronise MyISAM with InnoDB periodically using event scheduler. You risk that full text search would return stale data, but on the other hand this should have less of an impact on performance, and at least you know data is consistent after each sync.
Also some good news: starting with MySQL 5.6 InnoDB gets full text searches.
Related
I saw so many questions and answers on this topic MyISAM vs InnoDB on stackoverflow itself.
But, all of the questions and answers are too old and not related to the current stable version of MySQL 5.7.x
By the time so much development must have been done in both MyISAM and InnoDB.
So, I need those differences available presently with version 5.7.x
So, please don't mark my question duplicate and someone please explain the differences these storage engines have currently as well as the differences they have since past.
Also, please explain at what situation which storage engine should be chosen for a table.
Can different tables belonging to the same schema have different storage engines i.e. few tables will have InnoDB and few ones will have MyISAM.
If yes, then how the JOIN queries would get execute between tables with MyISAM and InnoDB?
Is it true that MySQL is going to remove MyISAM storage engine from the future version?
Your assumption that MyISAM has been receiving new development is not correct. MyISAM is not receiving any significant new development. MySQL is clearly moving in the direction of phasing out MyISAM, and using MyISAM is discouraged.
Oracle Corp. has not announced any specific date or version by which they will remove MyISAM. My guess is that MyISAM will never be fully removed, because there are too many sites that wouldn't be able to upgrade, without doing expensive testing to make sure their specific app won't experience any regression issues by converting to InnoDB.
But you might notice that in the MySQL 5.7 manual, the section on MyISAM has been demoted to Alternative Storage Engines, which should be a clue that it's receiving less priority.
In MySQL 5.7, MyISAM is still used for some of the system tables, like mysql.user, mysql.db, etc. But new system tables introduced in 5.6 and 5.7 are InnoDB. All system tables are InnoDB in MySQL 8.0.
MyISAM still does not support any of the properties of ACID. There are no transactions, no consistency features, and no durable writes. See my answer to MyISAM versus InnoDB.
MyISAM still does not support foreign keys, for what it's worth. But I seldom see real production sites using foreign keys even with InnoDB.
MyISAM supports only table-level locking (except for some INSERT appending to the end of a table, as noted in the manual).
MySQL 5.7 supports both fulltext indexes and spatial indexes in both MyISAM and InnoDB. These features are not reasons to continue using MyISAM as they once were.
Both logical backup tools like mysqldump and physical backup tools like Percona XtraBackup can't back up MyISAM tables without acquiring a global lock.
You asked if you could create a variety of tables with different storage engines in the same schema. Yes, you can, and this is the same as it has been for many versions of MySQL.
You asked if you can join tables of different storage engines (by the way, tables don't need to be in the same schema to be joined). Yes, you can join such tables, MySQL takes care of all the details. This is the same as it has been for many versions of MySQL.
But some weird cases can come up when you do this, like what if you update a MyISAM table and an InnoDB table in a transaction, and then roll back? The changes in the InnoDB table are rolled back, but the changes in the MyISAM table are not rolled back, so your data integrity can be broken if you aren't careful. This is also the same as it has been for many versions of MySQL.
Cases where MyISAM has an advantage over InnoDB is a short list, and it's getting shorter.
Some table-scan queries and bulk inserts are faster in MyISAM. InnoDB is better at indexed searches.
MyISAM may use less storage space than the equivalent data stored in an uncompressed InnoDB table. You can further compact MyISAM tables with myisampack, but this makes the MyISAM table read-only.
There are other options these days for compact storage of data in transactional storage engines, for example InnoDB table compression, or MyRocks.
SELECT COUNT(*) FROM MyTable queries (with no WHERE clause) are very fast in MyISAM, because the accurate count of rows is persisted in the MyISAM metadata. InnoDB (or other MVCC implementations) doesn't keep this count persisted, because every transaction viewing the table might "see" a different row count. Only a storage engine that has table-level locking and no transaction isolation like MyISAM, can optimize this case.
Auto-increment that numbers independently for each distinct value in another key column. Again, this requires table-level locking, so it's not supported in InnoDB.
CREATE TABLE MyTable (
group_id INT NOT NULL,
seq_id INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY (group_id, seq_id)
) ENGINE=MyISAM;
It's still easy to move a MyISAM table from server to server, because the .MYD and .MYI files are self-contained. You can kind of do something similar with InnoDB tables, but you have to use the intricate feature of transportable tablespaces. But this easy-to-move-tables quality of MyISAM no longer works in MySQL 8.0, because of their new data dictionary feature.
Under certain load, MyISAM might be a better choice for internal_tmp_disk_storage_engine, which defaults to InnoDB in MySQL 5.7. If you run lots of queries that create temp tables on disk (in-memory temp tables won't benefit), it can put a strain on the InnoDB engine. But you'd have to have a high query rate for this to matter, and if your queries create so many temp tables on disk, you should try to optimize the queries differently.
MyISAM allows you to set multiple key caches, and define caches for specific tables. But the MyISAM key caches are only for index structures, not for data.
References:
https://www.percona.com/blog/2016/10/11/mysql-8-0-end-myisam/
https://www.percona.com/blog/2017/12/04/internal-temporary-tables-mysql-5-7/
http://jfg-mysql.blogspot.com/2017/08/why-we-still-need-myisam.html
I had this question for a job quiz and got it right: (referring the new version):
MyISAM and InnoDB are two different storage engins that handle CRUD operations differently.
Locking: When approching a row inside a MyISAM storage engin, all the table will be locked by other sessions until the change is commited, unlike InnoDB, which locks only the specific selected row(/s). The lock is released until the session is commited. Locking a table or a row causes suspention by other sessions that try to interact with the same table or row to prevent wrong data manipulations in the table for example.
Transactions: InnoDB supports transactions, unlike MyISAM. Transactions are a colection of 2 or more commands like SELECT, INSERT, UPDATE and DELETE, to a single operation until complishion.
Atomic Operations: When setting a transaction in an InnoDB and
the operation is incompleted - it terminates all the changes and
restore the DB as it was (all or nothin'), so for example, if in the
middle of a transaction there is a syntax error in the code /
datatype mismatch or anything that might interupt the bundle of
commands to finish its operation - all the changes wont be applied,
thanks transactions atomicy. On the other hand, when using an
MyISAM storage engin, if a bundle of commands "breaks" (for any
reason), the operation stops immediately and all the
tables/rows/data that were affected will remain affected, which
might cause a corrupt data in the database (...and a headache).
B. Running an operation on MyISAM are set on the spot,
whereas InnoDB allows you to use the "ROLLBACK"s to discard any
change, which comes best in handy when running transactions.
Transaction Logs: When creating a transaction without a
transaction log in between, you can apply any changes on the table/s
in the DB, and if the table have a clustered index (for example),
the data will have to search where exactly it has to be inserted and
only then apply the change. In a case where there is a transaction
log in between the DB and the transaction, the changes will be sent
to the transaction log first and will set its order in the table
before sending the change to the DB - which will be less time
consuming. The DB saves logs from all the transactions that were
made, which can help to choose to restore any transaction previously
made, and recover all changes. When set to a "simple" recovery model- transactions are deleted from the transactions log and wont be able to recover data (used usually on DEV environments). When set to
"full" recovery model, all transactions are saved and listed, ready
to be restored - this is used usually on production environments
which might cause problems like preformance issues - so backing them
up and deleting from the server could be a solution. When set to a
"bulk-logged" recovery model saved transaction logs only for
specific "important" changes and commands (import,export,
insert-select, select-into, reorganaizing/rebuilding indexes), and
might prevent preformance issues.
Foreign keys: MyISAM dosn't use foreign keys, unlike InnoDB. When a table column has a foregin key set to point on an other table column, when any update/delete occures on the pointed table, it will know that the changes have to be applied on the other table pointing at it. This create a some kind of a link between the two table and keep data in sync. Setting tables with FKs might require more effort which might be considered as a disadvantage (?).
FULLTEXT indexing: InnoDB doesn't support FULLTEXT indexing in its previous versions - MyISAM does support it. Switching to MyISAM wont be the best solution so just update MySQL to a verion which does support FULLTEXT indexing.
FULLTEXT indexing can take texts like titles, comments, ect' - and search it (this should be a better option than the "LIKE" command in this case).
Spatial data types: Supported only on InnoDB.
To sum all up, InnoDB will be usually more reliable in terms of data handling, validity & recovery. For newer versions InnoDB will support FULLTEXT indexing for mainly searches - when using older versions with no option to update MySQL, using MyISAM will be great.
A Database already has up to 25-30 tables and all are MyISAM. Most of these tables are related to each other meaning a lot of queries use joins on IDs and retrieve data.
One of the tables contain 7-10 Million records and it becomes slow if i want to perform a search or update or even retrieval of all data. Now i proposed a solution to my boss saying that converting tables into InnoDB might give better performance.
I also explained the benefits of InnoDB:
Since we anyways join multiple tables on keys and they are related, it will be better to use foreign keys and have relational database which will avoid Orphan Rows. I found around 10-15k orphan rows in one of the big tables and had to manually remove them.
Support for transactions, we perform big updates from time to time and if one of them fails on the way we have to replace the entire table with the backed-up one and run the update again to make sure that all queries were executed. With InnoDB we can revert back any changes from query 1 if query 2 fails.
Now the response i got from my boss is that I need to prove that InnoDB will run faster than MyISAM. My question is, wont above 2 things improve the speed of the application itself by eliminating orphan rows?
In general is MyISAM faster than InnoDB?
Note: using MySQL 5.5
You should also mention to your boss probably the biggest benefit you get from InnoDB for large tables with both read/write load - You get row-level locking rather than table-level locking. This can be a great performance benefit for the application in cases where you see a lot of waits for table locks to be released.
Of course the best way to convince your boss is to prove it. Make copies of your large table and place on a testing database. Make one version of data in MyISAM and one in InnoDB. Then run load testing against it with a load mix that approximates your current DB read/write activity. Find out for yourself if it is better.
Just updated for your comment that you are on 5.5. With 5.5 it is a no brainer to use InnoDB. MyISAM engine basically has seen no improvement over the last several years and development effort has been around InnoDB. InnoDB is THE MySQL engine of choice going forward.
After repairing my database I received the following error:
scode_tracker.ap_visits
note : The storage engine for the table doesn't support repair
scode_tracker.visit_length
note : The storage engine for the table doesn't support repair
I found out that the type of table is InnoDB. The other table was MyISAM and it was repaired successfully.
After reading some topic here, the solution is to change it to MyISAM. I don't know much about InnoDB and MyISAM. I don't specify the type when I created the table. So my question is should I use MyISAM instead of InnoDB? If yes, how can I change it from InnoDB to MyISAM?
First is you have to understand the difference between MyISAM and InnoDB Engines. And this is clearly stated on this link. You can use this sql statement if you want to convert InnoDB to MyISAM:
ALTER TABLE t1 ENGINE=MyISAM;
InnoDB works slightly different that MyISAM and they both are viable options.
You should use what you think it fits the project.
Some keypoints will be:
InnoDB does ACID-compliant transaction. http://en.wikipedia.org/wiki/ACID
InnoDB does Referential Integrity (foreign key relations) http://www.w3resource.com/sql/joins/joining-tables-through-referential-integrity.php
MyIsam does full text search, InnoDB doesn't
I have been told InnoDB is faster on executing writes but slower than MyISAM doing reads (I cannot back this up and could not find any article that analyses this, I do however have the guy that told me this in high regard), feel free to ignore this point or do your own research.
Default configuration does not work very well for InnoDB needs to be tweaked accordingly, run a tool like http://mysqltuner.pl/mysqltuner.pl to help you.
Notes:
In my opinion the second point is probably the one were InnoDB has a huge advantage over MyISAM.
Full text search not working with InnoDB is a bit of a pain, You can mix different storage engines but be careful when doing so.
Notes2:
- I am reading this book "High performance MySQL", the author says "InnoDB loads data and creates indexes slower than MyISAM", this could also be a very important factor when deciding what to use.
You have the wrong table set on the command. You should use the following on your setup:
ALTER TABLE scode_tracker.ap_visits ENGINE=MyISAM;
I have a database with 48 tables and 45 of the tables are InnoDB.
I have 3 MyISAM tables which range in size from 200 records to 1.5Mil and also a 6.5Mil entries.
These 3 tables contain GEO Location information and are read only (never write - unless i was to update one - extremely infrequently).
I considered changing them to InnoDB to make the database 100% the same but then read the MYiSAM is faster. Note: I don't need any of the special INNODB functions - its just selects/joins... thats it.
Should I keep these MyISAM or change them to InnoDB?
thx
MyISAM used to be faster years ago, but if you use any reasonably current version of InnoDB, then InnoDB is faster for most workloads. Here's a performance comparison from way back in 2007 that shows InnoDB already matched or bettered MyISAM in all but a few types of queries.
http://www.mysqlperformanceblog.com/2007/01/08/innodb-vs-myisam-vs-falcon-benchmarks-part-1/
Since that test in 2007, InnoDB has continued to get better, whereas the MySQL developers have spent virtually no time improving MyISAM. It's dead, Jim.
The only cases where MyISAM may be faster is when doing full table-scans, and you should try to define indexes to avoid table-scans anyway.
InnoDB has been the default storage engine in MySQL since 5.5 (circa 2010). With each major version of MySQL, it becomes more clear that MyISAM is going away.
InnoDB has many benefits even if you don't use the explicit features like transactions or foreign keys. Try this:
Execute a long-running UPDATE against a MyISAM table.
Interrupt it partway through. How many rows have been changed? Some, but not all.
Repeat the same test with an InnoDB table. How many rows have been changed? Zero!
InnoDB supports atomic changes, so every SQL statement either succeeds completely, or else rolls back. You won't get partially-completed changes.
InnoDB also support crash recovery, so you won't lose data if mysqld ever crashes. MyISAM is renowned for corrupting tables during a crash.
InnoDB also caches data in RAM (the InnoDB buffer pool), whereas MyISAM relies on the filesystem cache to speed up data I/O. This makes some queries a lot faster in InnoDB if you have enough RAM.
Use MyISAM only if you don't care about your data.
No need to change In INNODB. As you say thay have lot of records SO thay are faster as MYISAM
MyISAM in most cases will be faster than InnoDB for run of the mill sort of work. Selecting, updating and inserting are all very speedy under normal circumstances.
I wouldn't bother changing it. I was just researching the same thing and came across this useful post: http://www.kavoir.com/2009/09/mysql-engines-innodb-vs-myisam-a-comparison-of-pros-and-cons.html
The main reason you'd want Innodb would be for data integrity and to avoid locking the entire table on inserts. But if you're not doing a lot of inserts and these are not high traffic tables, then why make the change?
No change is necessary, i am working on similar project where the database is going to be used for read-only and Myisam is the best option for it.
In addition you can even use sphinx if you want faster reads.
hope this helps.
I've read various threads about which is better between InnoDB and MyISAM. It seems that the debates are to use or the other. Is it not possible to use both, depending on the table?
What would be the disadvantages in doing this? As far as I can tell, the engine can be set during the CREATE TABLE command. Therefore, certain tables which are often read can be set to MyISAM, but tables that need transaction support can use InnoDB.
You can have both MyISAM and InnoDB tables in the same database. What you'll find though, when having very large tables is, MyISAM would cause table-lock issues. What this ultimately does is, it locks the whole table for a single transaction, which is very bad if you have many users using your website. e.g If you have a user searching for something on your site and the query takes minutes to complete, no other users could use your site during that period because the whole table is locked.
InnoDB on the other hand uses row-level locking, meaning, that row is the only row locked from the table during a transaction. InnoDB can be slower at searches because it doesn't offer full text search like MyISAM, but that isn't a big problem when you compare it to table-level locking of MyISAM. If you use InnoDB, like many large sites, then you could use a server side search engine like Sphinx for full text searches. Or you could even use a MyISAM table to do the searching like f00 suggested. I'd personally recommended InnoDB mainly because of the row-level locking feature, but also because you can implement full text searching in many other ways.
Basically, if you have a message board application with lots of selects, inserts as well as updates, InnoDB is probably the generally appropriate choice.
But if you're not building something like that (or any other thing with registered users) and your working mostly with static content (or more reads than writes), then you could use MyISAM.
Yes indeed you may use both in the same database, you may choose for each table separately.
In short, InnoDB is good if you are working on something that needs a reliable database that can handles a lot of INSERT and UPDATE instructions.
and, MyISAM is good if you needs a database that will mostly be taking a lot of read (SELECT) instructions rather than write (INSERT and UPDATES), considering its drawback on the table-lock thing.
you may want to check out;
Pros and Cons of InnoDB
Pros and Cons of MyISAM
You don't choose InnoDB or MyISAM on a database level, but instead on a table level. So within the one database you could have some tables running the InnoDB engine and some running MyISAM. As you pointed out, you could choose to use InnoDB on the tables that require transactions etc, and MyISAM where you need other features such as fulltext searching.