On 10.11.2017 12:15, Ashutosh Bapat wrote:
Maybe in this thread[1] your described problem are solved through
introducing Parallel Append node?
1.
https://www.postgresql.org/message-id/CAJ3gD9dy0K_E8r727heqXoBmWZ83HwLFwdcaSSmBQ1%2BS%2BvRuUQ%40mail.gmail.com
You may want to review [2] and [3] as well.
[2] https://www.postgresql.org/message-id/9666.1491295317@localhost
[3]
https://www.postgresql.org/message-id/CAM2+6=V64_xhstVHie0Rz=kpeqnljmzt_e314p0jat_oj9m...@mail.gmail.com
Thank you very much for this references.
I applied partition-wise-agg-v6 patches and for partitioned tables it
works perfectly:
shard=# explain select count(*) from orders;
QUERY PLAN
---------------------------------------------------------------------------------------
Finalize Aggregate (cost=100415.29..100415.30 rows=1 width=8)
-> Append (cost=50207.63..100415.29 rows=2 width=8)
-> Partial Aggregate (cost=50207.63..50207.64 rows=1 width=8)
-> Foreign Scan on orders_0 (cost=101.00..50195.13
rows=5000 width=0)
-> Partial Aggregate (cost=50207.63..50207.64 rows=1 width=8)
-> Foreign Scan on orders_1 (cost=101.00..50195.13
rows=5000 width=0)
(6 rows)
But I wonder why the same optimization is not applied to normal
inherited table:
shard=# explain select count(*) from base;
QUERY PLAN
----------------------------------------------------------------------------------
Aggregate (cost=44087.99..44088.00 rows=1 width=8)
-> Append (cost=0.00..39079.46 rows=2003414 width=0)
-> Seq Scan on base (cost=0.00..0.00 rows=1 width=0)
-> Seq Scan on derived1 (cost=0.00..14425.00 rows=1000000
width=0)
-> Seq Scan on derived2 (cost=0.00..14425.00 rows=1000000
width=0)
-> Foreign Scan on derived_fdw (cost=100.00..212.39
rows=3413 width=0)
(6 rows)
Are there some principle problems?
--
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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