Re: Making aggregate deserialization (and WAL receive) functions slightly faster

On Wed, Oct 04, 2023 at 07:47:11PM +1300, David Rowley wrote:
> The original patch had a new function in stringinfo.c which allowed a
> StringInfoData to be initialised from an existing string with some
> given length.  Tom wasn't a fan of that because there wasn't any
> protection against someone trying to use the given StringInfoData and
> then calling appendStringInfo to append another string. That can't be
> done in this case as we can't repalloc the VARDATA_ANY(state) pointer
> due to it not pointing directly to a palloc'd chunk.  Tom's complaint
> seemed to be about having a reusable function which could be abused,
> so I modified the patch to remove the reusable code.  I think your
> macro idea in stringinfo.h would put the patch in the same position as
> it was initially.

Ahem, well.  Based on this argument my own argument does not hold
much.  Perhaps I'd still use a macro at the top of array_userfuncs.c
and numeric.c, to avoid repeating the same pattern respectively two
and four times, documenting once on top of both macros that this is a
fake StringInfo because of the reasons documented in these code paths.
--
Michael