Re: [PROPOSAL] VACUUM Progress Checker.

On 11/24/15 2:02 AM, Amit Langote wrote:
>> 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.
> Just to clarify, does this mean we report index vacuum progress in terms
> of index items processed (not pages)? If so, how do we get total number of
> index items to process (presumably across all indexes) for a given phase 2
> round? As a context, we'd report phase 1 progress in terms of heap pages
> processed of total heap pages.

You'd get it from pg_class.reltuples for each index. Since all index
vacuuming is done strictly on a per-index-tuple basis, that's probably
the most accurate way to do it anyway.

Also, while it might be interesting to look at the total number of index
tuples, I think it's probably best to always report on a per-index
basis, as well as which index is being processed. I suspect there could
be a very large variance of tuple processing speed for different index
types. Eventually it might be worth it to allow index AMs to provide
their own vacuuming feedback, but I think that's way out of scope for
this patch. :)
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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