Re: SQLFunctionCache and generic plans

We get substantial wins on all of fx, fx3, fx4.  fx2 is the
case that gets inlined and never reaches functions.c, so the
lack of change there is expected.  What I found odd is that
I saw a small speedup (~6%) on fx5 and fx6; those functions
are in plpgsql so they really shouldn't change either.
The only thing I can think of is that I made the hash key
computation a tiny bit faster by omitting unused argtypes[]
entries.  That does avoid hashing several hundred bytes
typically, but it's hard to believe it'd amount to any
visible savings overall.

Anyway, PFA v10.

                        regards, tom lane

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