> > > # explain analyze select a%1000000,length(string_agg(b,',')) from ab > group > > by 1; > > QUERY PLAN > > > --------------------------------------------------------------------------------------------------------------------------- > > GroupAggregate (cost=119510.84..144510.84 rows=1000000 width=32) > (actual > > time=538.938..1015.278 rows=1000000 loops=1) > > Group Key: ((a % 1000000)) > > -> Sort (cost=119510.84..122010.84 rows=1000000 width=32) (actual > > time=538.917..594.194 rows=1000000 loops=1) > > Sort Key: ((a % 1000000)) > > Sort Method: quicksort Memory: 102702kB > > -> Seq Scan on ab (cost=0.00..19853.00 rows=1000000 width=32) > > (actual time=0.016..138.964 rows=1000000 loops=1) > > Planning time: 0.146 ms > > Execution time: 1047.511 ms > > > > > > Patched > > # explain analyze select a%1000000,length(string_agg(b,',')) from ab > group > > by 1; > > QUERY PLAN > > > ------------------------------------------------------------------------------------------------------------------------ > > HashAggregate (cost=24853.00..39853.00 rows=1000000 width=32) (actual > > time=8072.346..144424.872 rows=1000000 loops=1) > > Group Key: (a % 1000000) > > -> Seq Scan on ab (cost=0.00..19853.00 rows=1000000 width=32) > (actual > > time=0.025..481.332 rows=1000000 loops=1) > > Planning time: 0.164 ms > > Execution time: 263288.332 ms > > Well, that's pretty odd. I guess the plan change must be a result of > switching the transition type from internal to text, although I'm not > immediately certain why that would make a difference. >
It is strange, why hashaggregate is too slow? Pavel > > -- > Robert Haas > EnterpriseDB: http://www.enterprisedb.com > The Enterprise PostgreSQL Company > > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers >
