From: Jim Nasby <Jim.Nasby@BlueTreble.com>
To: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andreas Karlsson <andreas@proxel.se>
Cc: Julien Tachoires <julmon@gmail.com>
Cc: Alex Shulgin <ash@commandprompt.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Jaime Casanova <jaime@2ndquadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: patch : Allow toast tables to be moved to a different tablespace
Date: Tue, 14 Jul 2015 16:57:34 -0500
Message-ID: <55A585CE.306@BlueTreble.com> (raw)
In-Reply-To: <20150707120744.GM30359@alap3.anarazel.de>
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<550D6A82.2070208@proxel.se>
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<20150707120744.GM30359@alap3.anarazel.de>
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On 7/7/15 7:07 AM, Andres Freund wrote:
> On 2015-07-03 18:03:58 -0400, Tom Lane wrote:
>> I have just looked through this thread, and TBH I think we should reject
>> this patch altogether --- not RWF, but "no we don't want this". The
>> use-case remains hypothetical: no performance numbers showing a real-world
>> benefit have been exhibited AFAICS.
>
> It's not that hard to imagine a performance benefit though? If the
> toasted column is accessed infrequently/just after filtering on other
> columns (not uncommon) it could very well be beneficial to put the main
> table on fast storage (SSD) and the toast table on slow storage
> (spinning rust).
>
> I've seen humoungous toast tables that are barely ever read for tables
> that are constantly a couple times in the field.
+1. I know of one case where the heap was ~8GB and TOAST was over 400GB.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Data in Trouble? Get it in Treble! http://BlueTreble.com
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Cc: Jim.Nasby@BlueTreble.com, andres@anarazel.de, tgl@sss.pgh.pa.us, andreas@proxel.se, julmon@gmail.com, ash@commandprompt.com, alvherre@2ndquadrant.com, jaime@2ndquadrant.com, robertmhaas@gmail.com
Subject: Re: patch : Allow toast tables to be moved to a different tablespace
In-Reply-To: <55A585CE.306@BlueTreble.com>
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