From: Tom Lane <tgl@sss.pgh.pa.us>
To: Pavel Stehule <pavel.stehule@gmail.com>
cc: Dean Rasheed <dean.a.rasheed@gmail.com>,
        Justin Pryzby <pryzby@telsasoft.com>,
        Stephen Frost <sfrost@snowman.net>,
        Surafel Temesgen <surafel3000@gmail.com>,
        Alvaro Herrera <alvherre@2ndquadrant.com>,
        vignesh C <vignesh21@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@postgresql.org>,
        Daniel Gustafsson <daniel@yesql.se>
Subject: Re: proposal: possibility to read dumped table's name from file
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Comments: In-reply-to Pavel Stehule <pavel.stehule@gmail.com>
	message dated "Wed, 25 Nov 2020 20:29:00 +0100"
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Date: Wed, 25 Nov 2020 15:00:32 -0500
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Pavel Stehule <pavel.stehule@gmail.com> writes:
> st 25. 11. 2020 v 19:25 odesílatel Dean Rasheed <dean.a.rasheed@gmail.com>
> napsal:
>> I agree that being able to configure pg_dump via a config file would
>> be very useful, but the syntax proposed here feels much more like a
>> hacked-up syntax designed to meet this one use case, rather than a
>> good general-purpose design that can be easily extended.

> But I don't understand why? What is a use case? What is a benefit against
> command line, or libpq variables? And why should config files be better as
> a solution for limited length of command line, when I need to dump
> thousands of tables exactly specified?

Because next week somebody will want to dump thousands of functions
selected by name, or schemas selected by name, etc etc.  I agree with
the position that we don't want a single-purpose solution.  The idea
that the syntax should match the command line switch syntax seems
reasonable, though I'm not wedded to it.  (One thing to consider is
how painful will it be for people to quote table names containing
funny characters, for instance.  On the command line, we largely
depend on the shell's quoting behavior to solve that, but we'd not
have that infrastructure when reading from a file.)

> What are the benefits of supporting multiple formats?

Yeah, that part of Dean's sketch seemed like overkill to me too.

I wasn't very excited about multiple switch files either, though
depending on how the implementation is done, that could be simple
enough to be in the might-as-well category.

One other point that I'm wondering about is that there's really no
value in doing anything here until you get to some thousands of
table names; as long as the list fits in the shell's command line
length limit, you might as well just make a shell script file.
Does pg_dump really have sane performance for that situation, or
are we soon going to be fielding requests to make it not be O(N^2)
in the number of listed tables?

			regards, tom lane