Re: Memory leak in nodeAgg

Added to TODO:

* Consider simplifying how memory context resets handle child contexts

http://archives.postgresql.org/pgsql-patches/2007-08/msg00067.php

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Neil Conway wrote:
> 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).
>
> -Neil
>
>
>
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