Re: Binary search in fmgr_isbuiltin() is a bottleneck.

Andres Freund <andres@anarazel.de> writes:
> On 2017-10-05 17:08:39 +0300, Heikki Linnakangas wrote:
>> BTW, there's some alignment padding in FmgrBuiltin, when MAXIMUM_ALIGNOF==8.
>> You could easily shrink the struct from 32 to 24 bytes by moving funcName to
>> the end of the struct:

> Yea, that's probably worthwhile, although I suspect it's not a huge save
> overall. Do you just want to commit that?

+1

>> If we care about cache efficiency here, we could move funcName out of the
>> fmgr_builtins array, to a separate array of the same size.

> When'd that be beneficial? fmgr_builtins is pretty much only used for
> internal-language CREATE FUNCTIONs? In other cases oid bounds + mapping
> array should filter out the access before fmgr_builtins is accessed.

I'm -1 on this, it would complicate using the data structure to look up
the name of a built-in function from its OID.  (Don't know that anyone
actually does that, but I see no reason to break their code if they do.)

			regards, tom lane