Horton

Re: [HACKERS] Runtime Partition Pruning

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
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>
Date: 2019-05-24T16:24:28Z
Lists: pgsql-hackers 
Hi,

On 2019-05-24 12:08:57 -0400, Tom Lane wrote:
> 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%3DJvbUbnpWtrRZNey7hJ07%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?

I've not looked in a while, but I think at some point it was.


> 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.

Does that depend on whether the program was compiled with
-fno-omit-frame-pointer? At least some distros now compile with frame
pointers enabled, to get reasonably fast perf profiles (at a basically
immeasurable slowdown, on modern-ish CPUs).


> 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.

It's still a lot easier to install debug symbols than to attach a
debugger and get a backtrace that way. Especially when the problem is
hard to reproduce.

Greetings,

Andres Freund

Commits

  1. Initialize ExprStates once in run-time partition pruning

  2. Add bms_prev_member function

  3. Support partition pruning at execution time

  4. Document partprune.c a little better

  5. Fix crash in pg_replication_slot_advance

  6. Add parallel-aware hash joins.

  7. Fix typo.

  8. Allow --with-bonjour to work with non-macOS implementations of Bonjour.

  9. Mention need for --no-inc-recursive in rsync command