MySQL Field Index Limits

Is there any way of making MySQL index a field for more that 256 characters? We have about 2K of index-required data that needs to be lightening fast and we cannot find a way to do this. I have even tried changing the table type, but even this has not worked.

Help please!

Nope, you can't index BLOB and TEXT types. Not that it would likely be much help. When using a where clause on a large field, you would probably use a LIKE comparison using wildcards. Indexes can only utilitize a LIKE comparison if there is NO wildcard in the first character of the match, even on CHAR and VARCHAR types. Not likely when comparing a large text field.

The only solution that comes to mind is a table of keywords that you could extract from the large files, filtering out common words (and, but, if, the, etc.)

That would be a large table and preclude phrase searching, but would prevent using LIKE and wildcards to take advantage of indexing.