Re: Simple query seems to be ignoring date index

[Rick James]

If this is the most common query:
SELECT * FROM test WHERE Date='2008-10-1';
You need some INDEX _starting_ with Date.

PRIMARY KEY(Sym, Date), INDEX(Date)
or
PRIMARY KEY(Date, Sym), INDEX(Sym)

Either of those would provide the UNIQUEness constraint (the PRIMARY KEY). In MyISAM, either would make the allow that SELECT to be somewhat efficient. It will be even more efficient if the data is INSERTed in Date order. If you get new data each day, than that is the order of insertion.