Re: reducing the footprint of ScanKeyword (was Re: Large writable variables)

On 12/27/18, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> If you really are hot about saving that other 440 bytes, the way to
> do it would be to drop the struct entirely and use two parallel
> arrays, an int16[] for value and a char[] (or better uint8[]) for
> category. Those would be filled by reading kwlist.h twice with
> different definitions for PG_KEYWORD. Not sure it's worth the
> trouble though --- in particular, not clear that it's a win from
> the standpoint of number of cache lines touched.

Understood. That said, after re-implementing all keyword lookups, I
wondered if there'd be a notational benefit to dropping the struct,
especially since as yet no caller uses both token and category. It
makes pl_scanner.c and its reserved keyword list a bit nicer, and gets
rid of the need to force frontend to have 'zero' token numbers, but
I'm not sure it's a clear win. I've attached a patch (applies on top
of v6), gzipped to avoid confusing the cfbot.

-John Naylor