Query otimizing possible?

Hello,
I am workíng with Postgres95, and querys like
select * from lit_b where i1='n78' or il='ng798' or il='k45'
works very slow. There is an index on il, but it is obviously
used only when there is only one il='dd69' statement. For
example the time for doing the query increases from 3 seconds
to 3 minutes when using 2 il='dd69' statements. In this case the
class seems to be searched sequently.
Does anybody know a workaround for this Problem?

Thanks in advance
Andreas

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* Andreas Schmidt
* Institut fuer Kriminologie
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