Re: [PROPOSAL] VACUUM Progress Checker.

On Sat, Nov 21, 2015 at 12:38 AM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:
> On 11/19/15 7:29 PM, Amit Langote wrote:
>>>
>>> Another option is to provide the means for the index scan routines to
>>> >report their progress. Maybe every index AM won't use it, but it'd
>>> >certainly be a lot better than staring at a long_running boolean.
>>
>> The boolean would be a workaround for sure. I'm also slightly tempted by
>> the idea of instrumenting vacuum scans of individual index AM's bulkdelete
>> methods. One precedent is how vacuum_delay_point() are sprinkled around in
>> the code. Another problem to solve would be to figure out how to pass
>> progress parameters around - via some struct or could they be globals just
>> like VacuumCost* variables are...
>
> It just occurred to me that we could do the instrumentation in
> lazy_tid_reaped(). It might seem bad to do in increment for every tuple in
> an index, but we're already doing a bsearch over the dead tuple list.
> Presumably that's going to be a lot more expensive than an increment
> operation.

I think the cost of doing an increment there would be negligible. I'm
not quite sure whether that's the right place to instrument - though
it looks like it might be - but I think the cost of ++something in
that function isn't gonna be a problem at all.

--
Robert Haas
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