Re: [HACKERS] Custom compression methods (mac+lz4.h)

On Mon, Mar 22, 2021 at 11:48 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Anyway, this particular macro name was chosen, it seems, for symmetry
> > with VARDATA_4B_C, but if you want to change it to something else, I'm
> > OK with that, too.
>
> After looking at postgres.h for a bit, I'm thinking that what these
> should have been symmetric with is the considerably-less-terrible
> names used for the corresponding VARATT_EXTERNAL cases. Thus,
> something like
>
> s/VARRAWSIZE_4B_C/VARDATA_COMPRESSED_GET_RAWSIZE/
> s/VARCOMPRESS_4B_C/VARDATA_COMPRESSED_GET_COMPRESSION/

Works for me.

> Possibly the former names should survive and the latter become
> wrappers around them, not sure. But we shouldn't be using the "4B"
> terminology anyplace except this part of postgres.h.

I would argue that it shouldn't be used any place at all, and that we
ought to go the other direction and get rid of the existing macros -
e.g. change #define VARATT_IS_1B_E to #define VARATT_IS_EXTERNAL
instead of defining the latter as a no-value-added wrapper around the
former. Maybe at one time somebody thought that the test for
VARATT_IS_EXTERNAL might someday have more cases than just
VARATT_IS_1B_E, but that's not looking like a good bet in 2021.

--
Robert Haas
EDB: http://www.enterprisedb.com