Re: Hot Standby and 64+ subxids (was COPY enhancements)

Simon Riggs wrote:
> On Thu, 2009-10-08 at 11:50 -0400, Tom Lane wrote:
>
>> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>>
>>> Subcommitting every single row is going to be really painful,
>>> especially after Hot Standby goes in and we have to issue a WAL record
>>> after every 64 subtransactions (AIUI).
>>>
>> Yikes ... I had not been following that discussion, but that sure sounds
>> like a deal-breaker. For HS, not this.
>>
>
> Probably worth expanding this thought...
>
> HS writes a WAL record for subtransactions at the point that the subxid
> cache overflows for any single transaction. Current cache size = 64.
> Top-level transaction then writes one additional WAL record every
> additional 64 subxids after that. These are known as xid assignment
> records.
>
> If we execute transactions that completely fit in subxid cache we don't
> write any WAL records at all. There is no cumulative effect. So in most
> applications, we never write xid assignment records at all.
>
> Does that cover your objection, or do you see other issues?
>
>

I don't recall seeing an answer to this, and I can't find one on the
list archives either. Is it no longer an issue?

cheers

andrew