Date: Wed, 13 Mar 2019 14:38:02 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: hyrax vs. RelationBuildPartitionDesc
Message-ID: <20190313173802.GA24768@alvherre.pgsql>
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On 2019-Mar-13, Robert Haas wrote:

> On Wed, Mar 13, 2019 at 12:42 PM Alvaro Herrera
> <alvherre@2ndquadrant.com> wrote:
> > I remember going over this code's memory allocation strategy a bit to
> > avoid the copy while not incurring potential leaks CacheMemoryContext;
> > as I recall, my idea was to use two contexts, one of which is temporary
> > and used for any potentially leaky callees, and destroyed at the end of
> > the function, and the other contains the good stuff and is reparented to
> > CacheMemoryContext at the end.  So if you have any accidental leaks,
> > they don't affect a long-lived context.  You have to be mindful of not
> > calling leaky code when you're using the permanent one.
> 
> Well, that assumes that the functions which allocate the good stuff do
> not also leak, which seems a bit fragile.

A bit, yes, but not overly so, and it's less fragile that not having
such a protection.  Anything that allocates in CacheMemoryContext needs
to be very careful anyway.

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