On Fri, 13 Dec 2019 at 15:50, Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Fri, Dec 13, 2019 at 11:08 AM Masahiko Sawada > <masahiko.saw...@2ndquadrant.com> wrote: > > > > On Fri, 13 Dec 2019 at 14:19, Amit Kapila <amit.kapil...@gmail.com> wrote: > > > > > > > > > > > > > > > How about adding an additional argument to ReinitializeParallelDSM() > > > > > > that allows the number of workers to be reduced? That seems like it > > > > > > would be less confusing than what you have now, and would involve > > > > > > modify code in a lot fewer places. > > > > > > > > > > > > > > > > Yeah, we can do that. We can maintain some information in > > > > > LVParallelState which indicates whether we need to reinitialize the > > > > > DSM before launching workers. Sawada-San, do you see any problem with > > > > > this idea? > > > > > > > > I think the number of workers could be increased in cleanup phase. For > > > > example, if we have 1 brin index and 2 gin indexes then in bulkdelete > > > > phase we need only 1 worker but in cleanup we need 2 workers. > > > > > > > > > > I think it shouldn't be more than the number with which we have > > > created a parallel context, no? If that is the case, then I think it > > > should be fine. > > > > Right. I thought that ReinitializeParallelDSM() with an additional > > argument would reduce DSM but I understand that it doesn't actually > > reduce DSM but just have a variable for the number of workers to > > launch, is that right? > > > > Yeah, probably, we need to change the nworkers stored in the context > and it should be lesser than the value already stored in that number. > > > And we also would need to call > > ReinitializeParallelDSM() at the beginning of vacuum index or vacuum > > cleanup since we don't know that we will do either index vacuum or > > index cleanup, at the end of index vacum. > > > > Right.
I've attached the latest version patch set. These patches requires the gist vacuum patch[1]. The patch incorporated the review comments. In current version patch only indexes that support parallel vacuum and whose size is larger than min_parallel_index_scan_size can participate parallel vacuum. I'm still not unclear to me that using min_parallel_index_scan_size is the best approach but I agreed to set a lower bound of relation size. I separated the patch for PARALLEL_VACUUM_DISABLE_LEADER_PARTICIPATION from the main patch and I'm working on that patch. Please review it. [1] https://www.postgresql.org/message-id/CAA4eK1J1RxmXFAHC34S4_BznT76cfbrvqORSk23iBgRAOj1azw%40mail.gmail.com -- Masahiko Sawada http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
v36-0001-Add-index-AM-field-and-callback-for-parallel-ind.patch
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v36-0003-Add-FAST-option-to-vacuum-command.patch
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v36-0002-Add-parallel-option-to-VACUUM-command.patch
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