General question about speed of functions

I am starting a project next week that looks like it will involve some
massive sql rewrites to gain needed performance, and I am looking at
implementing as many functions as possible.  I haven't worried that much
about specific implementations in the past, but this project can use any
performance gains available, so even a five percent difference between a
function written in c vs pgsql would be helpful.

The apparent choices available for the existing application are to use
functions in pgsql, php or c.

Any comments about relative performance of using any of those languages
would be greatly appreciated.

Thanks,

Brent Friedman

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