Re: Parallel bitmap heap scan

On 2016-10-19 09:43:10 +0530, Dilip Kumar wrote:
> On Tue, Oct 18, 2016 at 1:42 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> > But what's the impact on performance? Presumably parallel bitmap heap
> > scan was already slower than the non-parallel version, and that commit
> > presumably widens the gap. Seems like something to worry about...
>
> I have checked the performance in my local machine and there is no
> impact on the gap.

Try measuring with something more heavy on bitmap scan time
itself. E.g.
SELECT SUM(l_extendedprice) FROM lineitem WHERE (l_shipdate >= '1995-01-01'::date) AND (l_shipdate <= '1996-12-31'::date);
or similar. The tpch queries don't actually spend that much time in the
bitmapscan itself - the parallization of the rest of the query is what
matters...

Greetings,

Andres Freund