On Thu, Apr 16, 2020 at 8:36 PM Ashutosh Bapat <ashutosh.bapat....@gmail.com> wrote:
> On Thu, Apr 16, 2020 at 7:47 AM Andy Fan <zhihui.fan1...@gmail.com> wrote: > > > (9 rows) > > > > With this feature: > > explain analyze select a, sum(c) from grp2 group by a; > > QUERY PLAN > > > -------------------------------------------------------------------------------------------------------------------------- > > GroupAggregate (cost=0.00..553031.57 rows=10000023 width=12) (actual > time=0.044..13209.485 rows=10000000 loops=1) > > Group Key: a > > -> Seq Scan on grp2 (cost=0.00..403031.23 rows=10000023 width=8) > (actual time=0.023..4938.171 rows=10000000 loops=1) > > Planning Time: 0.400 ms > > Execution Time: 13749.121 ms > > (5 rows) > > > > Applying the patch gives a white space warning > git am /tmp/v6-000* > Applying: Introduce UniqueKeys to determine RelOptInfo unique properties > .git/rebase-apply/patch:545: indent with spaces. > /* Fast path */ > warning: 1 line adds whitespace errors. > Applying: Skip DISTINCT / GROUP BY if input is already unique > > Compiling the patch causes one warning > nodeAgg.c:2134:3: warning: enumeration value ‘AGG_UNIQUE’ not handled > in switch [-Wswitch] > > Thanks, I will fix them together with some detailed review suggestion. (I know the review need lots of time, so appreciated for it). > I have not looked at the patch. The numbers above look good. The time > spent in summing up a column in each row (we are summing only one > number per group) is twice the time it took to read those rows from > the table. That looks odd. But it may not be something unrelated to > your patch. I also observed that for explain analyze select a from > grp2 group by a; we just produce a plan containing seq scan node, > which is a good thing. > Great and welcome back Ashutosh:) > -- > Best Wishes, > Ashutosh Bapat >
