Index merge join

Hi,

Best way to restrict query on many columns is to have index on these
columns.
BUT with faster and faster IOPS is it not already feasable to make
merge
join on indexes ? Then it could be possible to have just index on
single columns
for more rare queries. Index which have column and oid/primary key.
Then make merge join on all columns restreicted/sorted.
Same for full text search (word,relevance,id)

Best regards,
   Maek Mosiewicz