Re: Open Item: Should non-text EXPLAIN always show properties?

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Thu, Jun 25, 2020 at 8:42 AM James Coleman <jtc331(at)gmail(dot)com> wrote:
>> Yesterday I'd replied [1] to Justin's proposal for this WRT
>> incremental sort and expressed my opinion that including both
>> unnecessarily (i.e., including disk when an in-memory sort was used)
>> is undesirable and confusing and leads to shortcuts I believe to be
>> bad habits when using the data programmatically.

> +1.

I think the policy about non-text output formats is "all applicable
fields should be included automatically". But the key word there is
"applicable". Are disk-sort numbers applicable when no disk sort
happened?

I think the right way to think about this is that we are building
an output data structure according to a schema that should be fixed
for any particular plan shape. If event X happened zero times in
a given execution, but it could have happened in a different execution
of the same plan, then we should print X with a zero count. If X
could not happen period in this plan, we should omit X's entry.

So the real question here is whether the disk vs memory decision is
plan time vs run time. AFAIK it's run time, which leads me to think
we ought to print the zeroes.

regards, tom lane