Slow search on one table, many where, order by and limit

[Yair P]

Hi, on a dating site we have a big cards table (500k rows) with about 20 fields.

So cards table has a,b,c,d,e... fields and we run a search like:

select * from cards where a=_ and b=_ and c=_ and d=_ and e=_ order by j limit 100

The search takes several seconds to run.

The problem is that the user selects which parameters to use.
for example we may have:
select * from cards where b=_ and e=_ order by j limit 100
or
select * from cards where a=_ and d=_ and e=_ order by j limit 100

So we cannot just create index on a,b,c,d,e,j.

It is not practical to defined 32 different key combinations (2 to the power of 5)

Any suggestions?

Thanks