Date: Wed, 31 Jul 2019 11:23:22 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: vignesh C <vignesh21@gmail.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Unused header file inclusion
Message-ID: <20190731152322.GA30941@alvherre.pgsql>
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On 2019-Jul-31, vignesh C wrote:

> I noticed that there are many header files being
> included which need not be included.

Yeah, we have tooling for this already in src/tools/pginclude.  It's
been used before, and it has wreaked considerable havoc; see "git log
--grep pgrminclude".

I think doing this sort of cleanup is useful to a point -- as Andres
mentions, some includes are somewhat more "important" than others, so
judgement is needed in each case.

I think removing unnecessary include lines from header files is much
more useful than from .c files.  However, nowadays even I am not very
convinced that that is a very fruitful use of time, since many/most
developers use ccache which will reduce the compile times anyway in many
cases; and development machines are typically much faster than ten years
ago.

Also, I think addition of new include lines to existing .c files should
be a point worth specific attention in patch review, to avoid breaking
reasonable modularity boundaries unnecessarily.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services