From: Antonin Houska <ah@cybertec.at>
To: Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Gierth <andrew@tao11.riddles.org.uk>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Problems with plan estimates in postgres_fdw
Date: Mon, 18 Feb 2019 15:21:11 +0100
Message-ID: <30524.1550499671@localhost> (raw)
In-Reply-To: <5C6A5FD3.8080102@lab.ntt.co.jp>
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<1175.1533220908@sss.pgh.pa.us>
<5BB739CD.6040002@lab.ntt.co.jp>
<5BBC4140.50403@lab.ntt.co.jp>
<5C17A00E.5000005@lab.ntt.co.jp>
<5C232F39.9060509@lab.ntt.co.jp>
<5C25C7B5.2010802@lab.ntt.co.jp>
<5C518631.5080401@lab.ntt.co.jp>
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<5C5D778F.3080501@lab.ntt.co.jp>
<19433.1549962210@localhost>
<5C669DFD.30002@lab.ntt.co.jp>
<16616.1550234762@localhost>
<5C6A5FD3.8080102@lab.ntt.co.jp>
Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp> wrote:
> (2019/02/15 21:46), Antonin Houska wrote:
> > ok, I understand now. I assume that the patch
> >
> > https://www.postgresql.org/message-id/5C66A056.60007%40lab.ntt.co.jp
> >
> > obsoletes the code snippet we discussed above.
>
> Sorry, I don't understand this. Could you elaborate on that?
I thought that the assignments
+ startup_cost += outerrel->reltarget->cost.startup;
and
+ run_cost += outerrel->reltarget->cost.per_tuple * input_rows;
in the patch you posted in
https://www.postgresql.org/message-id/5C66A056.60007%40lab.ntt.co.jp do
replace
+ startup_cost += foreignrel->reltarget->cost.startup;
and
+ run_cost += foreignrel->reltarget->cost.per_tuple * rows;
respectively, which you originally included in the following part of
0001-postgres_fdw-Perform-UPPERREL_ORDERED-step-remotely-v3.patch:
@@ -2829,6 +2872,22 @@ estimate_path_cost_size(PlannerInfo *root,
run_cost += foreignrel->reltarget->cost.per_tuple * rows;
}
+ /*
+ * If this is an UPPERREL_ORDERED step on the final scan/join
+ * relation, the costs obtained from the cache wouldn't yet contain
+ * the eval cost for the final scan/join target, which would have been
+ * updated by apply_scanjoin_target_to_paths(); add the eval cost now.
+ */
+ if (fpextra && !IS_UPPER_REL(foreignrel))
+ {
+ /* The costs should have been obtained from the cache. */
+ Assert(fpinfo->rel_startup_cost >= 0 &&
+ fpinfo->rel_total_cost >= 0);
+
+ startup_cost += foreignrel->reltarget->cost.startup;
+ run_cost += foreignrel->reltarget->cost.per_tuple * rows;
+ }
+
/*
* Without remote estimates, we have no real way to estimate the cost
* of generating sorted output. It could be free if the query plan
--
Antonin Houska
Cybertec Schönig & Schönig GmbH
Gröhrmühlgasse 26, A-2700 Wiener Neustadt
Web: https://www.cybertec-postgresql.com
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To: pgsql-hackers@postgresql.org
Cc: ah@cybertec.at, fujita.etsuro@lab.ntt.co.jp, tgl@sss.pgh.pa.us, andrew@tao11.riddles.org.uk
Subject: Re: Problems with plan estimates in postgres_fdw
In-Reply-To: <30524.1550499671@localhost>
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