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

Andres Freund <andres@anarazel.de> writes:
> I might be worse than you... But anyway, here's a patch doing
> so. Looking at profiles, it turned out that having the integer limits as
> extern variables in a different TU isn't a great idea.

Uh, what?  Access to fmgr_nbuiltins shouldn't be part of any critical path
anymore after this change.

> So I moved what
> used to be fmgrtab.c to fmgrtab.h, and included it directly in fmgr.c.

I'm kind of -0.5 on that.  I believe part of the argument for having
things set up as they were was to allow external code to access the
fmgr_builtins table (as my speed-test hack earlier today did).
While I'm not sure that anything really is using that API, I do not
believe we'd gain any performance by removing it, so why do so?
We can leave the table and the fmgr_nbuiltins variable completely as-is,
and just add an index table, which fmgr.c could be aware is of size
exactly "FirstBootstrapObjectId" entries.

> Is this roughly what you were thinking of?

I think you need the "no entry" values to be -1; 0 is a valid index
into the fmgr table.
        regards, tom lane


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