Re: indexing on every column?

[Ben Hunter]

I was doing some research (because I'm trying to do the same things myself) and I have to retract some of my statements.

I thought I read somewhere that varchar(30) was better than varchar(255) in either performance or storage, if the largest string is 30 characters. I can't find this information again, and the stuff I'm reading seems to indicate that it doesn't necessarily make a difference (for values less than 256). Does an expert know for sure?

Also...I think the 'Fixed Width' row optimization would only apply to MyISM tables, not InnoDB. Or at least would do more for MyISM than InnoDB.

If you do create a couple of extra indexes, you could also configure the server/table to delay index flushes, so it will do a batch write to disk instead of a disk write every update.

And I'm wondering if a compound id,start_date index would help with the particular query you mentioned. Though if the ratio between id and start is small, it might be more effecient to just index on id. I guess some tests would say for sure.

Sorry...don't know any "just do this" solutions. Again...good luck!