Re: PATCH: logical_work_mem and logical streaming of large in-progress transactions

On Mon, Jan 6, 2020 at 3:56 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Mon, Jan 6, 2020 at 2:11 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > 3.
> > +static void
> > +ReorderBufferStreamTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
> > {
> > ..
> > + /*
> > + * If this is a subxact, we need to stream the top-level transaction
> > + * instead.
> > + */
> > + if (txn->toptxn)
> > + {
> > +
> > ReorderBufferStreamTXN(rb, txn->toptxn);
> > + return;
> > + }
> >
> > Is it ever possible that we reach here for subtransaction, if not,
> > then it should be Assert rather than if condition?
>
> ReorderBufferCheckMemoryLimit, can call it either for the
> subtransaction or for the main transaction, depends upon in which
> ReorderBufferTXN you are adding the current change.
>

That function has code like below:

ReorderBufferCheckMemoryLimit()
{
..
if (ReorderBufferCanStream(rb))
{
/*
* Pick the largest toplevel transaction and evict it from memory by
* streaming the already decoded part.
*/
txn = ReorderBufferLargestTopTXN(rb);
/* we know there has to be one, because the size is not zero */
Assert(txn && !txn->toptxn);
..
ReorderBufferStreamTXN(rb, txn);
..
}

How can it ReorderBufferTXN pass for subtransaction?

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com