Author Topic: MyISAM Drawbacks  (Read 4440 times)

sammyb

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MyISAM Drawbacks
« on: July 13, 2009, 05:50:10 PM »
I have installed OpenGoo on a shared host that does not allow InnoDB. In order for it to successfully install I used MyISAM. I browsed the forums trying to find out what problems or limits in functionality I can expect to run into. The only thing that I could find was that it "does not support transactions" (http://forums.opengoo.org/index.php?topic=523.0) . Could someone explain to me what that means? Also please let me know what other problems I can expect to find.

Thanks in advance.

ignacio

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Re: MyISAM Drawbacks
« Reply #1 on: August 28, 2009, 11:30:45 AM »
MyISAM seems to have worse performance for OpenGoo, noticeable only when heavily loaded. Not supporting transactions means that some data could remain inconsistent if an error occurs. A transaction works like this:

1) You begin a transaction
2) You perform modifications to the data
3) If an error occurs, you can "rollback" the transaction, which means that the data will be the same as it was on 1) so all modifications performed after don't take effect.
4) When you finish modifying data you "commit" the transaction, which means that the changes you made to the data are now permanent.

Since MyISAM doesn't support transactions, when an error occurs data cannot be restored to step 1), so some modifications could be partially made. For example, if you create a Note and an error occurs while saving it, it could happen that the note is created but the tags are not applied to the Note. This is just an invented example, but something similar to that could happen.

 

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