From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
        Alvaro Herrera <alvherre@alvh.no-ip.org>,
        Robert Haas <robertmhaas@gmail.com>,
        David Rowley <david.rowley@2ndquadrant.com>,
        Amit Langote <amitlangote09@gmail.com>,
        Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>,
        Jesper Pedersen <jesper.pedersen@redhat.com>,
        Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com>,
        Beena Emerson <memissemerson@gmail.com>, amul sul <sulamul@gmail.com>,
        "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>,
        Dilip Kumar <dilipbalaut@gmail.com>
Subject: Re: [HACKERS] Runtime Partition Pruning
In-reply-to: <20190524155818.wakkacerpl6yjguf@alap3.anarazel.de>
References: <20180410213203.nl645o5vj5ap66sl@alvherre.pgsql>
 <d4903af2-e7b7-b551-71f8-3e4a6bdc2e73@2ndquadrant.com>
 <16007.1558711252@sss.pgh.pa.us> <16535.1558712098@sss.pgh.pa.us>
 <20190524155818.wakkacerpl6yjguf@alap3.anarazel.de>
Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Fri, 24 May 2019 08:58:18 -0700"
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Date: Fri, 24 May 2019 12:08:57 -0400
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Andres Freund <andres@anarazel.de> writes:
> On 2019-05-24 11:34:58 -0400, Tom Lane wrote:
>> Hmm, after some digging in the archives, the closest thing I can find
>> is this thread:
>> https://www.postgresql.org/message-id/flat/CAMsr%2BYGL%2ByfWE%3DJvbUbnp=
WtrRZNey7hJ07%2BzT4bYJdVp4Szdrg%40mail.gmail.com
>> where we discussed using libunwind instead, but people didn't like
>> the extra dependency.

> Hm, I didn't actually see that much concern about that. I still think we
> should just go for libunwind.

Is it actually better?  The basic problem with backtrace() is that it
only knows about global functions, and so reports call sites in static
functions as if they were in whatever global function physically precedes
the static one.  I think doing materially better requires depending on
debug symbols, which (at least in the Red Hat world) aren't going to
be there in a typical production situation.

			regards, tom lane