in reply to
perl mysql full table scan
You might have to do both. Be sure, however, that MySQL is doing all the filtering that it can, because you don’t want to send those millions-of-rows across a network-wire between two servers, just to throw away nearly-all of them. (Whereas doing a local-disk-drive scan of millions of rows is actually not so bad.)
Also, seriously consider any features that MySQL may offer, including its word-based indexing capabilities for large-text fields. If you do this stuff “frequently,” it becomes the classic tradeoff of Speed vs. Space, in several ways. Benchmark your ideas carefully.