From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Stephen Frost <sfrost@snowman.net>
Cc: Michael Paquier <michael.paquier@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: Reviewing freeze map code
Date: Thu, 23 Jun 2016 18:59:57 -0400
Message-ID: <20160623225957.GA230122@alvherre.pgsql> (raw)
In-Reply-To: <20160623224224.ubztdvhfx6bwkphu@alap3.anarazel.de>
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Andres Freund wrote:
> I'm looking into three approaches right now:
>
> 3) Use WAL logging for the already_marked = true case.
> 3) This approach so far seems the best. It's possible to reuse the
> xl_heap_lock record (in an afaics backwards compatible manner), and in
> most cases the overhead isn't that large. It's of course annoying to
> emit more WAL, but it's not that big an overhead compared to extending a
> file, or to toasting. It's also by far the simplest fix.
I suppose it's fine if we crash midway from emitting this wal record and
the actual heap_update one, since the xmax will appear to come from an
aborted xid, right?
I agree that the overhead is probably negligible, considering that this
only happens when toast is invoked. It's probably not as great when the
new tuple goes to another page, though.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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Cc: alvherre@2ndquadrant.com, andres@anarazel.de, robertmhaas@gmail.com, amit.kapila16@gmail.com, thomas.munro@enterprisedb.com, sfrost@snowman.net, michael.paquier@gmail.com, sawada.mshk@gmail.com
Subject: Re: Reviewing freeze map code
In-Reply-To: <20160623225957.GA230122@alvherre.pgsql>
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