Robert Haas <robertmh...@gmail.com> writes:
> On Thu, Mar 14, 2019 at 3:13 AM Amit Langote
> <langote_amit...@lab.ntt.co.jp> wrote:
>> I'm curious why DestroyPartitionDirectory doesn't do
>> hash_destroy(pdir->pdir_hash)?

> What would be the point?  It's more efficient to let context teardown
> take care of it.

Agreed, but the comments in this area are crap.  Why doesn't
CreatePartitionDirectory say something like

 * The object lives inside the given memory context and will be
 * freed when that context is destroyed.  Nonetheless, the caller
 * must *also* ensure that (unless the transaction is aborted)
 * DestroyPartitionDirectory is called before that happens, else
 * we may leak some relcache reference counts.

It's completely not acceptable that every reader of this code should
have to reverse-engineer these design assumptions, especially given
how shaky they are.

There's an independent question as to whether the planner's use of
the feature is specifying a safe memory context.  Has this code been
exercised under GEQO?

                        regards, tom lane

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