Re: [PATCH] Incremental sort (was: PoC: Partial sort) - Mailing list pgsql-hackers

On Tue, Apr 07, 2020 at 08:40:30AM -0400, James Coleman wrote:
> On Tue, Apr 7, 2020 at 12:25 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
> > On Mon, Apr 06, 2020 at 09:57:22PM +0200, Tomas Vondra wrote:
> > > I've pushed the fist part of this patch series - I've reorganized it a
> >
> > I scanned through this again post-commit.  Find attached some suggestions.
> >
> > Shouldn't non-text explain output always show both disk *and* mem, including
> > zeros ?
>
> Could you give more context on this? Is there a standard to follow?
> Regular sort nodes only ever report one type, so there's not a good
> parallel there.

The change I proposed was like:

@@ -2829,7 +2829,6 @@ show_incremental_sort_group_info(IncrementalSortGroupInfo *groupInfo,

                ExplainPropertyList("Sort Methods Used", methodNames, es);

-               if (groupInfo->maxMemorySpaceUsed > 0)
                {
                        long            avgSpace = groupInfo->totalMemorySpaceUsed / groupInfo->groupCount;
                        const char *spaceTypeName;
...
-               if (groupInfo->maxDiskSpaceUsed > 0)
                {
...

To show in non-text format *both* disk and memory space used, even if zero.

I still think that's what's desirable.

If it's important to show *whether* a sort space was used, then I think there
should be a boolean, or an int 0/1.  But I don't think it's actually needed,
since someone parsing the explain output could just check
|if _dict['Peak Sort Space Used'] > 0: ...
the same as you're doing, without having to write some variation on:
|if 'Peak Sort Space Used' in _dict and _dict['Peak Sort Space Used'] > 0: ...

-- 
Justin