In Mysql (5.7 onwards) for Change tracking of a table, this approach is very simple to implement.
But it needs the versions table to be of MyISAM, which does table level locking.
Would this approach work well for production systems where multiple inserts/updates are happening every second?
Does any one have any real production systems experience about this approach?
Each table in the DB(InnoDB) has Versions table(MyISAM)
My system has the following load.
* Approx 500 reads/sec on each table due to various joins.
* And 50 writes/sec to various tables which have triggers to the versions table.
Would the versions table (MyISAM) become a bottleneck for performance?
When a MyISAM table has AUTO_INCREMENT (and a certain mode set), and no other UNIQUE keys, it will append to the table "without a lock". So, I don't think the 50 writes/sec will be an issue.
MariaDB will probably continue to include MyISAM long after Oracle jettisons it. Oracle's intent is to make InnoDB so good that there will be no need for MyISAM, and they are likely to succeed.
Secondary indexes on the versions tables may become a bottleneck. In this area, I think InnoDB's "change buffer" does a better job than MyISAM's "do it now".
Related
I have a Myisam table with composite unique key of 2 columns and 90 million data. Now we are facing memory and load issues and after going through the web I am planning to include partitioning and changing this table to Innodb for better performance. But I have following concerns:
Changing to innodb will have a huge downtime, Is it possible to minimize the downtime?
Most of the select query are on a particular column of the key on which I am planning to have the hash partitioning, how much it will effect the query on another key column?
Will these changes improve the performance to the extent mentioned theoretically? Is there any better solution for such cases. Any suggestion or experience can be helpful.
My queries are simple like
Select * from Table where Col1= "Value"
Select * from Table where Col1="Value" and Col2 IN (V1,V2,V3)
Inserts are very frequently.
InnoDB will probably help some. Conversion to InnoDB comes with some issues, as I state in My conversion blog.
Partitioning, per se, buys no performance gain. My partitioning blog lists 4 cases where you can, with design changes, gain performance.
Regardless of the Engine, your two queries will both benefit from
INDEX(col1, col2)
No form of partitioning will help. HASH partitioning is especially useless.
Conversion to InnoDB will take a lot of downtime, unless pt-online-schema-change will work for your case. Research it.
Also read my answers and comments on
Can i set up Mysql to auto-partition?
for more specifics.
It may be that adding that index is the main performance gain. But you have to do a lengthy ALTER to get it. MyISAM does not have ALGORITHM=INPLACE.
Innodb (about perfomance we are talking now) have sense only when there are alot of inserts and updates to your table, because of row-locking table.
If the most queries on your table are SELECTs then MyIsam will be faster.
Advice: put in my.cnf key_buffer_size equal to 25% of your free RAM.
If inserts on your database are very frequent, you will likely gain performance by switching to innodb, which won't lock down entire tables to insert, allowing other clients to select data concurrently.
Regarding question #1, if you are worried about downtime, I'd suggest you find a parallel dump/load solution for migrating your data to innodb. if you simply run an ALTER statement on your tables, this is a single threaded operation which will be much slower.
Regarding #2, you'd have to post a schema along with your partitioning strategy and the queries you are worried about.
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 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.
Sometimes I got asked on some interviews: what benefits does InnoDB have against MyISAM and when MyISAM is better than InnoDB? It's all clear about the first part of question: InnoDB is transaction compliant, row-level blocking instead of table-level blocking, foreign key support and some others, these points just came to mind immidiately.
But when MyISAM is really better than InnoDB?
MyISAM is better than InnoDB when you don't need those advanced features and storage speed is more important than other concerns. MyISAM also allows full-text searches to be performed inside the database engine itself, instead of needing to query results and then search them as an array or whatever in your application.
InnoDB is a reasonable choice if you need to store data with a high degree of fidelity with complicated interactions and relationships. MyISAM is a reasonable choice if you need to save or load a large number of records in a small amount of time.
I wouldn't recommend using MyISAM for data that matters. It's great for logging or comments fields or anything where you don't particularly care if a record vanishes into the twisting nether. InnoDB is good for when you care about your data, don't need fast searches and have to use MySQL.
It's also worth mentioning that InnoDB supports row-level locking, while MyISAM only supports table-level locking - which is to say that for many common situations, InnoDB can be dramatically faster due to more queries executing in parallel.
The bottom line: Use InnoDB unless you absolutely have to use MyISAM. Alternatively, develop against PostgreSQL and get the best of both.
MyISAM doesn't support transactions (and the other things mentioned) so it can work faster. MyISAM is a way to achieve higher performance in those situations when you do not need these features.
MyISAM supports full text, as mentioned, but also supports the MERGE table type. This is handy when you have a large table and would like to "swap" out/archive parts of it periodically. Think about a logging or report data that you want to keep the last quarter and/or year. MyISAM handles large amounts of data like this better, when you are mainly inserting and rarely updating or deleting.
InnoDB performance drops pretty quickly and dramatically once you can't fit the indexes in memory. If your primary key is not going to be a number (i.e. auto increment), then you may want to rethink using InnoDB. The primary key is replicated for every index on an InnoDB table. So if you have a large primary key and a few other indexes, your InnoDB table will get very large very quick.
There are a few features that MySQL only has implemented for MyISAM (such as native fulltext indexing).
That said, InnoDB is still typically better for most production apps.
Also: Full-text search in mySQL is only supported in myISAM tables.
MyISAM has a very simple structure, when compared with InnoDB. There is no row versioning, there's one file per table and rows are stored sequentially. However, while it supports concurrent inserts (SELECTs and 1 INSERT can run together), it also has table-level locks (if there are 2 INSERTs on the same table, 1 has to wait). Also, UPDATEs and DELETEs are slow because of the structure of the data files.
MyISAM doesn't support transactions or foreign keys.
Generally, MyISAM should be better if you work on general trends (so you don't care about the correctness of individual rows) and data is updated by night or never. Also, it allows to move individual tables from one server to another, via the filesystem.
InnoDB supports very well concurrency and transactions. Has a decent support for fulltext and an almost-decent support for foreign keys.
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.