Re: PATCH: index-only scans with partial indexes

Hi,

On 03/30/2016 06:01 AM, Kyotaro HORIGUCHI wrote:
> Thank you for polishing this.
>
> At Tue, 29 Mar 2016 13:31:19 -0500, Kevin Grittner <kgrittn@gmail.com> wrote in
<CACjxUsNm9+tn0Hat0p4wR+sF0bfQDYMPLOEw7FyDycQ2UUrbyA@mail.gmail.com>
>> I tried to whip this into shape, but there were a few areas I
>> didn't feel I had the necessary understanding to feel comfortable
>> taking on the committer role for it.  I've cleaned it up the best I
>> could, fixing whitespace and typos, eliminating an unnecessary
>> addition of an include, improving C comments (at least to my eye),
>> and adding an Assert where it seemed like a good idea to me.
>
> Especially for this one,
>
> ===
> @@ -2697,6 +2697,7 @@ check_partial_indexes(PlannerInfo *root, RelOptInfo *rel)
>              continue;            /* don't repeat work if already proven OK */
>
>          have_partial = true;
> +        break;
>      }
>      if (!have_partial)
>          return;
> ===
>
> The initialization has been moved to set_rel_size so the break
> can be restored.

FWIW the break was restored in the v9 by me.

>
>
>> My own tests and those of others show performance improvements (up
>> to 10x for some tests) and no significant performance degradation,
>> even with attempts to create "worst case" scenarios.
>>
>> The only changes to the regression tests are to change an "out"
>> file to eliminate re-checking the index predicate against the heap
>> on every matching row, which seems like a good thing.
>>
>> I'm taking my name off as committer and marking it "Ready for
>> Committer".  If someone else wants to comment on the issues where
>> Tom and Kyotaro-san still seem unsatisfied to the point where I
>> can get my head around it, I could maybe take it back on as
>> committer -- if anyone feels that could be a net win.
>
> FWIW, as mentioned upthread, I added the following condition to
> decline ripping index predicates from base restrictinfo without
> understanding the reason to do so.

Ummmm, I'm a bit confused. Which condition?

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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