Re: WIP: parallel GiST index builds

On 7/30/24 1:31 PM, Andrey M. Borodin wrote:>> On 30 Jul 2024, at 14:57, 
Tomas Vondra <tomas.vondra@enterprisedb.com> wrote:
>>
>>>
>>> How do we synchronize Shared Fake LSN with global XLogCtl->unloggedLSN? Just bump XLogCtl->unloggedLSN if necessary?
>>> Perhaps, consider using GetFakeLSNForUnloggedRel() instead of shared counter? As long as we do not care about FakeLSN>RealLSN.
>>>
>>
>> I'm confused. How is this related to unloggedLSN at all?
> 
> Parallel build should work for both logged and unlogged indexes.
> If we use fake LSN in shared memory, we have to make sure that FakeLSN < XLogCtl->unloggedLSN after build.
> Either way we can just use XLogCtl->unloggedLSN instead of FakeLSN in shared memory.
> 
> In other words I propose to use GetFakeLSNForUnloggedRel() instead of "pg_atomic_uint64 *fakelsn;”.

Yeah,

Great point, given the ugliness of passing around the fakelsn we might 
as well just use GetFakeLSNForUnloggedRel().

Andreas