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Re: Composite index
Posted by: Rick James
Date: August 29, 2016 11:34PM

I don't see the PRIMARY KEY in the table definition. It is picking that.

If this were InnoDB (which should be faster because of the clustering of the PK), the secondary key would be slower. It could be that the Optimizer is assuming InnoDB, hence the bias toward the PK.

Instead of "select id,cookie", you could do simply "SELECT 1" -- all you need to know is a yes/no answer.

Are most 'users' validated? That is, how often do you expect this query to 'fail'?

After a user is validated, how many more SQL queries will he perform? I am suggesting that this query is only a small fraction of the total activity, but you are treating it as if that is virtually the only thing to worry about.

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