Re: pg_waldump's inclusion of backend headers is a mess

Hi,

On 2017-02-13 22:42:00 -0500, Robert Haas wrote:
> I dug into the problem and discovered that pg_waldump is slurping up a
> tremendous crapload of backend headers. It includes gin.h,
> gist_private.h, hash_xlog.h, nbtree.h, and spgist.h, which all end up
> including amapi.h, which includes genam.h, which includes tidbitmap.h.

Right. Hard to avoid with the current organization - IIRC Alvaro, I (and
others?) had talked about doing more agressive reorganization first, but
the patch was already big enough...

> When you make tidbitmap.h include utils/dsa.h, it in turn includes
> port/atomics.h, which has an #error preventing frontend includes

Has to, because otherwise there's undefined variable/symbol references
on some, but not all, platforms.

> There are a number of ways to fix this problem; probably the cheapest
> available hack is to stick #ifndef FRONTEND around the additional
> stuff getting added to tidbitmap.h. But that seems to be attacking
> the problem from the wrong end.

Agreed.

> Therefore, I proposed the attached patch, which splits spgxlog.h out
> of spgist_private.h, nbtxlog.h out of nbtree.h, gistxlog.h out of
> gist_private.h, and ginxlog.h and ginblock.h out of gin_private.h.
> These new header files are included by pg_waldump in lieu of the
> "private" versions. This solves the immediate problem and I suspect
> it will head off future problems as well.
>
> Thoughts, comments, objections, better ideas?

No better ideas. I'm a bit concerned about declarations needed both by
normal and xlog related routines, but I guess that can be solved by a
third header as you did.

> +++ b/src/include/access/nbtxlog.h
> @@ -0,0 +1,255 @@
> +/*-------------------------------------------------------------------------
> + *
> + * nbtree.h
> + * header file for postgres btree xlog routines

Wrong file name.

Greetings,

Andres Freund