Re: Memory leak in nodeAgg

From: Neil Conway <neilc(at)samurai(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: Memory leak in nodeAgg
Date: 2007-08-07 00:13:35
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-patches

On Mon, 2007-08-06 at 18:52 -0400, Tom Lane wrote:
> Hmm. Good catch, but I can't help wondering if this is just the tip
> of the iceberg. Should *every* MemoryContextReset be
> MemoryContextResetAndDeleteChildren?

Yeah, the same thought occurred to me. Certainly having the current
behavior as the default is error-prone: it's quite easy to leak child
contexts on Reset. Perhaps we could redefine Reset to mean
ResetAndDeleteChildren, and add another name for the current Reset
functionality. ResetAndPreserveChildren, maybe?

> If we redefined MemoryContextReset to be the same as
> MemoryContextResetAndDeleteChildren, it'd be possible to keep the
> headers for child contexts in their parent context, thus easing
> traffic in TopMemoryContext, and perhaps saving a few pfree cycles
> when resetting the parent

The fact that MemoryContextCreate allocates the context header in
TopMemoryContext has always made me uneasy, so getting rid of that would
be nice. I wonder if there's not at least *one* place that depends on
the current Reset behavior, though...

> Anyone want to investigate what happens if we make MemoryContextReset
> the same as MemoryContextResetAndDeleteChildren?

Sure, I'll take a look, but I'll apply the attached patch in the mean
time (above cleanup is probably 8.4 material anyway).


In response to


Browse pgsql-patches by date

  From Date Subject
Next Message Tom Lane 2007-08-07 00:18:38 Re: Memory leak in nodeAgg
Previous Message Tom Lane 2007-08-06 22:52:13 Re: Memory leak in nodeAgg