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

On Tue, Aug 25, 2020 at 10:41 AM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Tue, Aug 25, 2020 at 9:31 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> >
> > I think the existing design is superior as it allows the flexibility
> > to create transaction files in different temp_tablespaces which is
> > quite important to consider as we know the files will be created only
> > for large transactions. Once we fix the sharedfileset for a worker all
> > the files will be created in the temp_tablespaces chosen for the first
> > time apply worker creates it even if it got changed at some later
> > point of time (user can change its value and then do reload config
> > which I think will impact the worker settings as well). This all can
> > happen because we set the tablespaces at the time of
> > SharedFileSetInit.
>
> Yeah, I agree with this point, that if we use the single shared
> fileset then it will always use the same tablespace for all the
> streaming transactions. And, we might get the benefit of concurrent
> I/O if we use different tablespaces as we are not immediately flushing
> the files to the disk.
>

Okay, so let's retain the original approach then. I have made a few
cosmetic modifications in the first two patches which include updating
docs, comments, slightly modify the commit message, and change the
code to match the nearby code. One change which you might have a
different opinion is below:

+ case WAIT_EVENT_LOGICAL_CHANGES_READ:
+ event_name = "ReorderLogicalChangesRead";
+ break;
+ case WAIT_EVENT_LOGICAL_CHANGES_WRITE:
+ event_name = "ReorderLogicalChangesWrite";
+ break;
+ case WAIT_EVENT_LOGICAL_SUBXACT_READ:
+ event_name = "ReorderLogicalSubxactRead";
+ break;
+ case WAIT_EVENT_LOGICAL_SUBXACT_WRITE:
+ event_name = "ReorderLogicalSubxactWrite";
+ break;

Why do we want to name these events starting with name as Reorder*? I
think these are used in subscriber-side, so no need to use the word
Reorder, so I have removed it from the attached patch. I am planning
to push the first patch (v53-0001-Extend-the-BufFile-interface) in
this series tomorrow unless you have any comments on the same.

--
With Regards,
Amit Kapila.