[TYPO3-dev] TYPO3 4.1 INNODB

[Martin Kutschker]

R. van Twisk schrieb:
> Dmitry Dulepov wrote:
> 
>> Hi!
>>
>> Steffen Müller wrote:
>>  
>>
>>> Dmitry, could you please explain why "InnoDB is more stable than MyISAM
>>> and prevents database corruption at peaks"?
>>> I did not yet read about that.
>>>     
>>
>>
>> Mysql does its best to prevent simultaneous writes to myisam tables. 
>> It relies on locks (normally file locks) when user tries to write to 
>> myisam table. However this does not always work as expected, 
>> especially at peak hours. Sometimes at least two writes still happen 
>> and table immediately becomes corrupted. Search English list archives, 
>> you will find several questions about corrupted tables. I had those 
>> too several times, when mysql has to process over 700qps (as mytop 
>> reports). At one point crashes started to appear every day. I searched 
>> inet and found various posts about it that generally recommended to 
>> move to innodb. I did that more than half a year ago and did not have 
>> *any* table corruptions on those tables even though load increased.
>>
>> InnoDb uses row transaction internally even if user did not start it 
>> explicitly. While myisam locks the whole table at write, innodb locks 
>> only space for one row. See the advantage? You can have many clients 
>> writing to table at once with InnoDB, who are well separated. But you 
>> cannot have more than one write to myisam table (performance killer!) 
>> and if it happens, your table dies immediately!
>>
>> InnoDb, of course, has its disadvantages. If "select count(*) from 
>> table" takes very little time/resources on myisam (because count is 
>> stored in table itself), innodb has to really count rows. But this is 
>> not a problem for typo3 because typo3 does not have such queries :)
>>
>> But there is one more advantage for Innodb. Myisam keeps indexes 
>> separately from row data. Thus if row pointer is found, myisam engine 
>> has to do one  more seek to data. Innodb keeps indexes together with 
>> rows, so it does not have to seek again.
>>
>> In general, I think innodb is much better for typo3 than myisam. I 
>> really did several days of research before switching.
>>
>>   
> 
> Hey Dmitry,
> 
> I also have seen the same behavior of myissam table, so whatever we can 
> move out of
> myisam when innodb is available would be great.
> 
> If you read the thread '[TYPO3-dev]  Indexed Search Performance 
> Improvement' people are finding
> a way to improve indexed search using full text indexes. However full 
> text search doesn't work on
> innodb, something to take into consideration.

AFAIK innodb is just a table type. So you can store all tabels as InnoDb 
and still have the indexed search data as MyISAM.

Masi