Improve Seq scan performance

Dear List,

I would like to improve seq scan performance. :-)

I have many cols in a table. I use only 1 col for search on it.  It is
indexed with  btree with text_pattern_ops. The search method is: r like
'%aaa%'
When I make another table with only this col values, the search time is
better when the data is cached. But wronger when the data isn't in cache.

I think the following:
- When there is a big table with many cols, the seq search is read all
cols not only searched.
- If we use an index with full values of a col, it is possible to seq
scan over the index is make better performance (lower io with smaller data).

It is possible to make an index on the table, and make a seq index scan
on this values?

Thanks for helping.

Best Regards,
    Ferenc