Re: question re internal functions requiring initdb

Tom Lane wrote:
> Joe Conway <mail(at)joeconway(dot)com> writes:
>>It made me wonder why don't we always create internal functions this
>>way, or at least all except a core set of bootstrapped functions.
>
> I don't believe it will actually work: you *must* add an internal
> function to include/catalog/pg_proc.h, or it won't get into the function
> lookup table that's built by Gen_fmgrtab.sh.
>
> It is true that you don't have to force an initdb right away, but
> there's an efficiency penalty IIRC (can't bypass the lookup table
> search, or something ... read the fmgr code for details).
>

OK -- I see what you mean now. For a *user alias* of an existing builtin
function fmgr_isbuiltin(), which does a binary search on the sorted
fmgr_builtins array, will fail. So there is a speed penalty in that the
function is looked up with fmgr_lookupByName(), which does a sequential
scan through the fmgr_builtins array.

Regardless, if the function is not listed in the fmgr_builtins array at
all, which it won't be if Gen_fmgrtab.sh doesn't see it in pg_proc.h,
then the lookup will fail entirely. I guess I would have found this out
on my own if I had carried the experiment out a little farther. Shucks!

Joe