Problem getting plpgsql to choose the right query plan

Hi,

I'm having trouble making plpgsql choose the right query plan for a
query. From what I understand from googling around, my problem happens
because plpgsql is very eager to cache query plans, and therefore often
works with "worst-case-scenario" query plans.

The query I'm trying to optimize is of this type:

SELECT column1,column2,column3 FROM places WHERE upper(placename) LIKE
upper($1);

When I run it manually with a constant the query takes something like
30ms, but when it's run in a plpgsql function it takes about 5 seconds.
I've narrowed it down to plpgsql deciding to use a sequential scan,
because it can't really know beforehand if the LIKE-string will be of
the form 'somewhere%' or '%somewhere%'. The first case can make use of a
varchar_pattern_ops index I've made, while the other one doesn't have
much choice but to use a sequential scan. Is there any way for me to
force plpgsql not to use a cached query plan, but instead figure out
what's best based on the LIKE-string that actually get passed to the
function?

Regards,

Helge Elvik