Re: WIP: parallel GiST index builds

> On 22 Jul 2024, at 14:53, Tomas Vondra <tomas.vondra@enterprisedb.com> wrote:
> 
> 
> 
> On 7/22/24 13:08, Andrey M. Borodin wrote:
>> 
>> 
>>> On 22 Jul 2024, at 12:26, Tomas Vondra
>>> <tomas.vondra@enterprisedb.com> wrote:
>>> 
>>> I don't understand how would that solve the problem, can you
>>> elaborate? Which of the values are you suggesting should be
>>> replaced with the shared counter? lastlsn?
>> 
>> I think during build we should consider index unlogged and always use
>> GetFakeLSNForUnloggedRel() or something similar. Anyway we will
>> calllog_newpage_range(RelationGetNumberOfBlocks(index)) at the end.
>> 
> 
> But that doesn't update the page LSN, which GiST uses to detect
> concurrent splits, no?

During inserting tuples we need NSN on page. For NSN we can use just a counter, generated by gistGetFakeLSN() which in turn will call GetFakeLSNForUnloggedRel(). Or any other shared counter.
After inserting tuples we call log_newpage_range() to actually WAL-log pages.
All NSNs used during build must be less than LSNs used to insert new tuples after index is built.


Best regards, Andrey Borodin.