Re: [HACKERS] Parallel Aggregate

[Paul Ramsey]

On December 21, 2015 at 2:33:56 AM, Haribabu Kommi (kommi.harib...@gmail.com) 
wrote:
Yes the query is producing more groups according to the selectivity. 
For example - scan selectivity - 400000, the number of groups - 400 

Following is the query: 

SELECT tenpoCord, 
SUM(yokinZandaka) AS yokinZandakaxGOUKEI, 
SUM(kashikoshiZandaka) AS kashikoshiZandakaxGOUKEI, 
SUM(kouzasuu) AS kouzasuuxGOUKEI, 
SUM(sougouKouzasuu) AS sougouKouzasuuxGOUKEI 
FROM public.test01 
WHERE tenpoCord <= '001' AND 
kamokuCord = '01' AND 
kouzaKatujyoutaiCord = '0' 
GROUP BY kinkoCord,tenpoCord; 
Shouldn’t parallel aggregate come into play regardless of scan selectivity? I 
know in PostGIS land there’s a lot of stuff like:

SELECT ST_Union(geom) FROM t GROUP BY areacode;

Basically, in the BI case, there’s often no filter at all. Hoping that’s 
considered a prime case for parallel agg :)

P