Compiling without libpq

Hello,

what is the difference in compiling with or without libpq?
I understand that without libpq is convenient if you do not have
PostgreSQL installed on the system, but then why would I want to
compile with libpq?
I see in configure script that openssl is disabled if I compile without
libpq. Why is that and what functionality do I loose exactly?
The reason I am asking is that I would like to make a package for it
for Haiku and I would like to know if is worth it to see if I need to
create two packages (one for users who have PostgreSQL installed and
one for those without it).

Thanks for any help,

Mark Hellegers

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