Date: Sat, 7 Apr 2018 18:13:31 -0300
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: 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>,
	Robert Haas <robertmhaas@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
Message-ID: <20180407211331.6idzpqp3wsusevwh@alvherre.pgsql>
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I pushed this patch -- 0001, 0002 and 0003 only.  I did not include
anything from 0004 and 0005; I didn't even get to the point of reading
them, so that I could focus on the first part.

I did not find anything to complain about.  I made a few adjustments and
asked David to supply a paragraph for perform.sgml (the "Using EXPLAIN"
section) which is included here.  I also adopted Jesper's (actually
David's) suggestion of changing "Partitions Pruned" to "Partitions
Removed" in the EXPLAIN output.

I had reservations about a relation_open() in the new executor code.  It
seemed a bit odd; we don't have any other relation_open in the executor
anywhere.  However, setting up the pruneinfo needs some stuff from
relcache that I don't see a reasonable mechanism to pass through
planner.  I asked Andres about it on IM and while he didn't endorse the
patch in any way, his quick opinion was that "it wasn't entirely
insane".  I verified that we already hold lock on the relation.


While we didn't get fast pruning support for MergeAppend or the
DELETE/UPDATE parts, I think those are valuable and recommend to
resubmit those for PG12.

Thank you!

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