mysql table 2 unique column

I have a table, called tablen.

It has this structure:

CREATE TABLE `tablen` (
   `a` int(11) unsigned not null,
   `b` int(11) unsigned not null,
   unique key(a,b)
}

This table has 1 use. I hit it with a row of data. If it is found to be a new unique row not already in the table, it gets added, else I get the returned error code.

The main thing I guess is speed. I don't have the facility to stress test the setup at the moment and so...

What would you say is the best format for this table?

Inn开发者_JAVA百科odb or myisam?

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If you have a lot of inserts and updates, go for InnoDB, because it has row locking. MyISAM has table locking, which means, the whole table gets locked when a record is inserted (queuing all other inserts). If you have far more selects than inserts/updates then use MyISAM which is usually faster there (if you also don't care for foreign keys).