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

On Fri, Jul 10, 2020 at 11:01 AM Ajin Cherian <itsajin(at)gmail(dot)com> wrote:
>
>
>
> On Fri, Jul 10, 2020 at 3:11 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>>
>> With your changes sometimes due to incomplete toast
>> changes, if it can not pick the largest top txn for streaming it will
>> hang forever in the while loop, in that case, it should go for
>> spilling.
>>
>> while (rb->size >= logical_decoding_work_mem * 1024L)
>> {
>> /*
>> * Pick the largest transaction (or subtransaction) and evict it from
>> * memory by streaming, if supported. Otherwise, spill to disk.
>> */
>> if (ReorderBufferCanStream(rb) &&
>> (txn = ReorderBufferLargestTopTXN(rb)) != NULL)
>>
>>
>
> Which is this condition (of not picking largest top txn)? Wouldn't ReorderBufferLargestTopTXN then return a NULL? If not, is there a way to know that a transaction cannot be streamed, so there can be an exit condition for the while loop?

Okay, I see, so if ReorderBufferLargestTopTXN returns NULL you are
breaking the loop. I did not see the other part of the patch but I
agree that it will not go in an infinite loop.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com