Re: Perform streaming logical transactions by background workers and parallel apply

On Fri, Feb 10, 2023 at 1:32 PM houzj(dot)fnst(at)fujitsu(dot)com
<houzj(dot)fnst(at)fujitsu(dot)com> wrote:
>
> On Tuesday, February 7, 2023 11:17 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Mon, Feb 6, 2023 at 3:43 PM houzj(dot)fnst(at)fujitsu(dot)com
> > <houzj(dot)fnst(at)fujitsu(dot)com> wrote:
> > >
> > > while reading the code, I noticed that in pa_send_data() we set wait
> > > event to WAIT_EVENT_LOGICAL_PARALLEL_APPLY_STATE_CHANGE while
> > sending
> > > the message to the queue. Because this state is used in multiple
> > > places, user might not be able to distinguish what they are waiting
> > > for. So It seems we'd better to use WAIT_EVENT_MQ_SEND here which will
> > > be eaier to distinguish and understand. Here is a tiny patch for that.
> > >
>
> As discussed[1], we'd better invent a new state for this purpose, so here is the patch
> that does the same.
>
> [1] https://www.postgresql.org/message-id/CAA4eK1LTud4FLRbS0QqdZ-pjSxwfFLHC1Dx%3D6Q7nyROCvvPSfw%40mail.gmail.com
>

My first impression was the
WAIT_EVENT_LOGICAL_PARALLEL_APPLY_SEND_DATA name seemed misleading
because that makes it sound like the parallel apply worker is doing
the sending, but IIUC it's really the opposite.

And since WAIT_EVENT_LOGICAL_PARALLEL_APPLY_LEADER_SEND_DATA seems too
verbose, how about shortening the prefix for both events? E.g.

BEFORE
WAIT_EVENT_LOGICAL_PARALLEL_APPLY_SEND_DATA,
WAIT_EVENT_LOGICAL_PARALLEL_APPLY_STATE_CHANGE,

AFTER
WAIT_EVENT_LOGICAL_PA_LEADER_SEND_DATA,
WAIT_EVENT_LOGICAL_PA_STATE_CHANGE,

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Kind Regards,
Peter Smith.
Fujitsu Australia