Random note of encouragement
Hey All,
I've been doing some (futile) work trying to speed up aggregates with a group by in PostgreSQL 9.5.
I installed PostgreSQL 9.6 on the same machine to see if I could get anything running in parallel when using partitioning - which didn't work.
But - I did find this:
With the following setup:
CREATE TABLE base(
view_time TIMESTAMP WITHOUT time ZONE,
view_time_day TIMESTAMP WITHOUT time ZONE,
count_n numeric);
INSERT INTO base
SELECT view_time,
date_trunc('day', view_time),
COUNT::numeric,
FROM
(SELECT
TIMESTAMP '2015-12-01' + random() * interval '30 days' AS view_time,
trunc(random() * 99 + 1) AS COUNT
FROM generate_series(1,30000000)) a;
analyze base;
Now when I run the following SQL (multiple times to allow for getting everything into shared buffers, which is 4GB on my machine):
select sum(count_n) from base group by view_time_day;
I get the following results:
PSQL 9.5 - ~21 secondsPSQL 9.6 devel - ~8.5 seconds
I think that's pretty good!
I know this is a devel release, things may change, blah blah. But still, something has changed for the better here!
I get the same plan on both nodes:
HashAggregate (cost=670590.56..670590.95 rows=31 width=13)Group Key: view_time_day-> Seq Scan on base (cost=0.00..520590.04 rows=30000104 width=13)
Cheers,
James Sewell,
PostgreSQL Team Lead / Solutions Architect
______________________________________
James Sewell,
PostgreSQL Team Lead / Solutions Architect
______________________________________
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