I like this idea in general. I'm envisioning a cool explain display in
pgAdmin that's updated live, as the query is executed, showing how many
tuples a seq scan in the bottom, and an aggregate above it, has
processed. Drool.
Currently the interface is that you open a new connection, and signal
the backend using the same mechanism as a query cancel. That's fine for
the interactive psql use case, but seems really heavy-weight for the
pgAdmin UI I'm envisioning. You'd have to poll the server, opening a new
connection each time. Any ideas on that? How about a GUC to send the
information automatically every n seconds, for example?
Other than that, this one seems to be the most serious issue:
Tom Lane wrote:
> Gregory Stark <stark@enterprisedb.com> writes:
>> There are downsides:
>
> Insurmountable ones at that. This one already makes it a non-starter:
>
>> a) the overhead of counting rows and loops is there for every query execution,
>> even if you don't do explain analyze.
I wouldn't be surprised if the overhead of the counters turns out to be
a non-issue, but we'd have to see some testing of that. InstrEndLoop is
the function we're worried about, right?
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com