Re: Decoding speculative insert with toast leaks memory

On Thu, Mar 25, 2021 at 11:04 AM Ashutosh Bapat
<ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
>
> Hi All,
> We saw OOM in a system where WAL sender consumed Gigabttes of memory
> which was never released. Upon investigation, we found out that there
> were many ReorderBufferToastHash memory contexts linked to
> ReorderBuffer context, together consuming gigs of memory. They were
> running INSERT ... ON CONFLICT .. among other things. A similar report
> at [1]
>
..
>
> but by then we might have reused the toast_hash and thus can not be
> destroyed. But that isn't the problem since the reused toast_hash will
> be destroyed eventually.
>
> It's only when the change next to speculative insert is something
> other than INSERT/UPDATE/DELETE that we have to worry about a
> speculative insert that was never confirmed. So may be for those
> cases, we check whether specinsert != null and destroy toast_hash if
> it exists.
>

Can we consider the possibility to destroy the toast_hash in
ReorderBufferCleanupTXN/ReorderBufferTruncateTXN? It will delay the
clean up of memory till the end of stream or txn but there won't be
any memory leak.

--
With Regards,
Amit Kapila.