MySQL Performance Example Was: Seriously, WTF?

[Iain Barnett]

On 9 May 2008, at 11:02 am, Christopher Jones wrote:

>
> Since `chr` is a set of defined values, at some point I did have it  
> as an ENUM. But then I read somewhere that this is bad, so it got  
> changed to VARCHAR. I always assumed that VARCHAR was better than  
> CHAR, and that the length didn't matter because it was  
> variable....! So is ENUM bad? Would it be better/worse than CHAR?


Int, enum, char in that order.

I'd avoid enum and just create a 'chr' table with an identity/auto- 
increment column as the pk, stick an index on it (if mySQL hasn't set  
one up on the pk) and join it to the histones table. No problem with  
adding new records to chr, or in the gotchas about dealing with  
enums. Then the multiple column index on histones will (should:)  
perform faster.


Iain