Re: To index or not index .... Help needed

[Daniel Nichter]

He already tried this too: "Even if I define an index on type and year only I get the same performance decrease." -- Personally, I've not ever heard of an index being slower than a table scan on a large amount of rows. If this were my problem, on a quiet test server I'd run each query and look at the Handler_read% values (SHOW STATUS LIKE 'Handler_read%'; -- remember to FLUSH STATUS; in between queries). That might provide some insight into what's happening.

You have free key buffer space and RAM correct? If you're out of RAM and your server is swapping the key buffer, this might explain it.